1Research Viticulturalist, Plant Pathologist (formerly with Colorado State University), andResearch Plant Pathologist and Cooperative Extension Fruit Disease Specialist, respectively.Colorado State University, Colorado Agricultural Experiment Station - Orchard MesaResearch Center, 3168 B.5 Road, Grand Junction, CO 81503.

THE COLORADO GRAPEGROWERS' GUIDE

1998 Edition

by

Richard A. Hamman1, Jr., Steven D. Savage, and Harold J. Larsen

Additional copies of this publication available from: The Other Bookstore: Cooperative Extension Resource Center

115 General Services BuildingColorado State UniversityFort Collins, CO 80523

(970) 491-6198

TABLE OF CONTENTS

IntroductionIntroduction 1Anatomy of the Grapevine 2Grapevine Structures 3

Establishing a VineyardSite Selection 4Common Mistakes in Vineyard DevelopmentPlant Selection 7Planning a Commercial Vineyard in Colorado 8Nursery Stock and Standards 9Phylloxera/Rootstocks 10Site Preparation 13Vineyard Development Checklist 14Trellising/Training 15Planting -- The First Year 18Grow tubes 21The Training Year (Year 2) 22The Third Year 26

Maintaining a VineyardWater Management 29Protection Against Winter Injury 30Frost Protection and Damage TreatmentPruning 32Bleeding 36Re-training Winter Damaged VinesShoot Tying and Suckering 39Shoot ThinningLeaf Removal 40Crop ThinningHedging 41Nutrition Analysis and Foliar Sprays

Zinc, Manganese, & IronCrop Estimation 45Harvest Timing 47

Sugar content, acidity, pH, & sampling

Pest Management / ControlDisease Management 49Powdery mildew, crown gall, Botrytis bunch rot, sour bunch rot,& virus diseases.Powdery Mildew Fungicide Program 49Insect & Mite Pest Management 57Nematodes 61Weed Management 62Bird Control 63

Wine Grape VarietiesWhite Varieties -- Vinifera Cultivars 65White Varieties -- Hybrid Cultivars 67Red Varieties -- Vinifera Cultivars 68Red Varieties -- Hybrid Cultivars 69Relative Cold Hardiness of Grapevines 70

Table Grape VarietiesHimrod, Interlaken, Lakemont, etc. 71

Vine SourcesNurseries 74Vineyard Supply Sources 75

Cost EstimatesVineyard Establishment Costs 78Vineyard Production Costs 79

Useful Books and PublicationsBooks and Publications 80Viticulture Trade Magazines 82Resources on the Internet 82

(The print version includes Cornell UniversityGrape IPM Sheets, not available in this CD-ROMversion.)

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Introduction

Wine grapes have been grown in severalcounties of Colorado since the end of the lastcentury. A renewed interest in wine grapecultivation was initiated during the mid-70's andthe most dramatic growth of the Colorado WineIndustry is occurring this decade. Since 1990,vineyard acreage has increased from 242 to over400 acres. State production levels have alsoincreased from 107 tons to 755 tons and maturevineyards in 1997 averaged 3.4 tons/acre. Thecurrent and future market for Colorado winegrapes appears healthy with 21 licensed wineriesthat have the capacity to produce approximately215,000 gallons of wine or the equivalent of 1,300tons. Ninety percent of the Colorado acreage is inMesa and Delta counties. The issues of coldclimate limitations on wine grape culture are ofextreme importance to Colorado growers. It hasbeen demonstrated that with careful site selection,varietal selection and use of proper viticulturalmanagement techniques, vineyards can toleratewinter conditions to a degree that allows theirsurvival in selected locations in Colorado. Winterhardiness is the only limiting factor for grapeculture in the state, since many severe disease andinsect pest problems do not yet play an importantrole.

The unique aspects of grape growing inColorado are the indirect effects of high elevation.Most suitable sites lie between 4,500 and 6,000feet above sea level – substantially higher thanmost growing regions of the world. The highelevation is accompanied by an extremely dryclimate. Because of these factors the regionexperiences intense sunlight and large dailytemperature fluctuations. These features fosterhigh pigment production and high acid, retentionin most grape varieties just as they do for thetraditional peach and apple crops of the area. Thus, grapes that survive Colorado winters canmature and produce fruit with highly desirablewine making characteristics.

As grape growing is both uncommon andin a sense new in Colorado, many gaps remain in

our knowledge of optimal growing practices. Theviticulture program at Colorado State UniversityOrchard Mesa Research Center is currentlyaddressing the unique problems facing Coloradogrowers. The CSU viticulture program providesgrowers and vintners with technical assistance andconducts applied research and fielddemonstrations in wine grape production.Colorado State University Orchard Mesa ResearchCenter is located at 3168 B½ Road, GrandJunction, Colorado 81503, 970-434-3264.

This publication is intended to presentwhat has been learned about the particular needsof grapes in a high desert region. The experienceof many growers is included as well as that fromthe test vineyard at the Colorado State UniversityOrchard Mesa Research Center.

Many people contributed to thepreparation of this new edition and their help hasbeen truly appreciated. Special recognition is dueto the pioneering grape growers of Colorado andthe visiting scientists who have shared theirexperience and knowledge with us over the lastdecade.

Where trade names are used, nodiscrimination is intended, and no endorsement byColorado State University is implied.

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Figure 1. Anatomy of the grapevine.

3

Figure 2. Grapevine structures.

4

Common Mistakes That Can Cause Poor Vineyard Development

Site: planting in the wrong site (poor drainage)Vine purchase: poor qualityTiming of planting: planting too late in the seasonIrrigation system: inadequate or not installed, poor use

Establishing a Vineyard

Site SelectionThere are limits to the absolute cold

temperatures that grapevines can survive, and thesuitability of a location greatly depends on thefrequency of large temperature changes. Ingeneral, arid continental weather is subject todramatic changes and thus grape survival isfeasible only in restricted areas that are somehowbuffered from these changes. Large bodies ofwater, lacking in Colorado, moderate temperaturechanges. In the high desert region, the mildest,most buffered climates occur in certain majorriver valleys such as the Grand Valley of theColorado, the North Fork Valley of the Gunnisonand the Arkansas River Valley near Canon City. The protection afforded by these geologic featuresis beyond the scope of this publication, but thehistoric success of other fruit crops often is thebest indicator of a location's suitability for grapeproduction.

Within these major areas, localizedmicroclimates play an important role in thefeasibility of planting grapes on a specific site. The most important feature is cold air drainage(See Figure 1). Under calm conditions, the earthradiates energy to the sky and receives heat fromthe air closet to it.

Cold air is heavier than warm and sinks to theground; the gradient formed (cold air below towarm air above) is called an inversion. Cold airalso acts like a liquid and flows to the lowestpoint. Slopes of two to three percent aresufficient to allow much of the cold air to moveaway, drawing down warmer air from higherlayers. This process is extremely important indetermining how cold a specific site will becomeon a calm, clear night. Temperature differences ofas much as 10oF can occur in sites that are in closeproximity, but have different cold air drainagecharacteristics. Often the coldest wintertemperatures and the most damaging spring frostsoccur during calm nights following the generalcooling by a storm or cold front. Sites that escapespring frosts also will often be warmer duringmidwinter episodes. Such differences can becritical for vine damage. Because grapes startgrowth fairly late in Colorado (usually earlyMay), there is only a short period during whichfrost damage may occur. Frost is actually a threatover a longer period in California and other majorgrape growing regions. As a rule of thumb, avoidplanting wine grapes where there are 150 frost-free days or less.

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Figure 3. Vineyard site selection factors.

The exposure of a slope relative to the sunis a more complicated factor. During the day, asouth or west facing slope will be some-whatwarmer throughout the year; however, this featureis not necessary to ripen grapes in Colorado eventhough it is important in other locations such asnorthern Germany. In fact, warming of soil on asouth slope during the winter in Colorado canreduce winter survival.

Soils can play an important role in grapesurvival and potential wine quality. Ideal soils aredeep, well-drained and not overly fertile. Suchsoils are difficult to find in many parts ofColorado with a climate sufficient for grapegrowth. For this reason, the limits due to

undesirable soil types need to be discussed.Deep soils - at least 3 to 5 feet - are needed

to discourage shallow rooting. Many cultivatedsoils are sufficiently deep, but have formed clayhardpans. This can prevent grapes from rootingdeeply, which is their natural growthcharacteristic. Checking for hardpans and takingsteps to eliminate them (i.e., deep ripping) arecritical steps in vineyard establishment; hardpansor other obstructions to deep water percolationneed to be avoided or changed. The grape growermust be able to control the water status of the soilto manage vine hardiness. Extremely gravellysoils can prove difficult to water adequately in thesemi-arid climate of Colorado; however,

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extremely heavy clay soils that cannot be drainedshould be avoided.

Grapevines have lower requirements formineral nutrient levels than many other crops. Therefore, few soils require substantialfertilization to support grapes. High nitrogenavail-ability can inhibit the transition of grapesfrom vegetative to fruiting to dormant states andthus should be used with caution.

High salt is a more common soil problemthan over/underfertility in western Colorado. Theparent materials for many soils in the area are veryhigh in calcium sulfates (gypsum) and carbonates. Grapes are not tolerant of high salts, and thusunleached soils or spots that accumulate saltsthrough seepage and evaporation will not supportvine growth. Analyze soil samples for a plantingsite. These tests include a check of soilconductivity which is an indication of salt content. Conductivities of less than 4 mmhos/cm areconsidered safe. Those above 6 mmhos/cm areconsidered to be very damaging to grapes. Checkthe salt content at various depths at the plantingsite; a low salt content near the surface does notguarantee a low salt content at a depth of 2 to 3feet. In soils with previous cropping history, onegenerally encounters salt problems in discreetareas fed by seepage from irrigation canalsystems. Areas with high water tables also areunsuitable for grapes due to high salts andexcessive moisture.

Areas with sufficiently low salt levels arecommon, and it is possible to maintain low saltlevels with low volume irrigation systems.

However, true drip systems can accumulate saltsif insufficient volume is applied.

A vineyard must have good quality wateravailable throughout the growing season; waterfrom drain ditches should not be used because ofpossible high salt content or unknown pesticideresidue. Water is required during April to Mayfor planting. Irrigation systems must beoperational before planting occurs. Finally,midwinter desiccation can kill many vines inColorado and must be prevented with a late fallirrigation to recharge the soil reservoirintentionally dried out after harvest. This is bestapplied after a frost to prevent any possibility ofthe vine's returning to a vegetative state.

Other factors to consider in site selectionare wind, hail, deer and birds. Extremely windysites could be troublesome due to mechanical vinedamage and desiccation. Certain locations maytend to have a higher probability of hail damage. Check with neighbors for historical weatherpatterns. Bird feeding is a common problem insmall vineyards with trees or other refuges forbirds nearby. Deer and elk can cause majordamage to both mature and immature vines. Fencing is the most effective means of control.

In summary, critical aspects to avoid invineyard site selection are frost pockets, shallowor poorly drained soils, high salt accumulations,poorly irrigated and overfertilized locations. Desirable factors include unobstructed slopes, andrelatively deep and well drained salt free soilswithout serious nutrient imbalances.

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Figure 4. Wine grape varieties by acreage in Colorado. Source: 1997 CSU grower survey.

Plant SelectionOnce a suitable site is chosen, many

critical decisions and steps must be taken beforethe grapes arrive. Perhaps the most criticaldecision is which grape varieties to utilize. (Note:It is often necessary to place orders nine months toa year ahead of planting). Relatively few of thethousands of grape varieties known are of anypresent or potential commercial value. The grapegrower must consider the relative winterhardiness, marketability, and potential quality ofthe variety when grown in Colorado. Visit 4 or 5wineries and determine what varieties arecurrently in demand and what the future marketlooks

like (See Figure 4). Additionally, manyvarieties have not been tested in Colorado. Even so, there are many varieties where notenough is known to either stronglyrecommend or tentatively discourage theirplanting. Wine grape varieties are presentedin Section V and table grape varieties arediscussed in Section VI.

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Planning a Commercial Vineyard in Colorado

Considerable planning and investigativework is needed before planting a vineyard on anew site. This preliminary work can minimize orprevent future problems and often can determineultimate success or failure. Some questions thatmust be addressed are as follows.

Economic Considerations: Will thisproject be economically viable? Gather allinformation possible and look carefully at start-upcosts and annual expenses; then evaluate yourprojected returns. Market potential must beexplored before planting grapes. Ask severallocal wineries what varieties they are currentlybuying and what they anticipate buying in 3 years. Ask them the current price per ton paid for thesevarieties. Supply and demand often directly affectwinegrape prices.

Climate: Is it suitable or not? Winegrapes have been successfully grown in over60 countries with a variety of climates. Between160-200 frost free days are needed to mature fruitof many varieties grown in Colorado. Mid-winterlow temperatures of -10oF and lower can injure orkill buds and canes. Weather data gathered on thevineyard site are invaluable, however, be cautiouswhen interpreting weather data obtained from astation located some distance from the actualvineyard site. Temperature differences of 10oF ormore between the station and vineyard may occur.

Site: What is a good site? Site selectioncannot be over emphasized. Planting the vineyardin the wrong site can be very discouraging andcostly. Continual retraining and low productionare frustrating and labor intensive. The idealvineyard site will be sloped (hill sides are best)and have very well drained soil with no hard pans. Avoid low lying valleys or areas where water andcold air naturally settle.

Water: Is irrigation water availablewhen you need it? Most fruit growing areas inwestern Colorado are irrigated by open ditchesfrom either rivers or reservoirs. Checkavailability of the irrigation water throughout the

growing season. Grapevines typically usebetween 20-25 inches of moisture per seasondepending on conditions (soil, climate, etc.). Have the water analyzed if you suspect high saltcontent or if you are pumping from a well.

It is critical that an irrigation system thatcan supply adequate water for young vines isfunctional before planting begins. The mostimportant aspect of the irrigation system is that itbe reliable. Much of the acreage being newlyplanted is using micro-irrigation rather thansurface irrigation. Both systems will grow grapeshowever, the micro-irrigation system hasadvantages such as; maintaining soil moisture atan optimum level, increased irrigation efficiency,improved chemical application, reduced weedgrowth, automation, and adaptability to difficultsoil and terrain conditions.

Previous crop history? Observe othercrops that are growing on or adjacent to theproposed vineyard site. These crops can givevaluable clues to problem areas. Poor growth andlow production may indicate problem areas andthe need for further investigation. Subsurfacewater created by over-watering neighbors can be aproblem. Careful observation of irrigationpractices of land uphill and adjacent to yourproposed vineyard site can help identify the needfor a drainage system or an alternate site.

Any wildlife problems? Some vineyardsites are excellent homes for rabbits, prairie dogs,deer and elk. These animals can causeconsiderable damage to new or establishedvineyards if preventative measures are not taken.

If you suspect these animals are near bybut see no evidence or signs, check with neighborswho may have historical knowledge of wildlifepatterns in the area.

Fencing may be required before plantingyour vineyard.

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Figure 5. Typical nursery grading differences. The 2 YR #1 cutting is most desirable followed by the 1 YR #1 and then#2 cutting.

Nursery Stock and Standards The majority of grapevines are sold as

dormant rooted cuttings. The dormant rootedcuttings are either grafted or self rooted. Theserooted cuttings are graded by nursery industrystandards.

Becoming familiar with these standardscan make the difference between success andfailure. Figure 5 demonstrates the relative sizedifferences between a 2 year number 1 dormantrooted cutting and a 1 year number cutting andwill transplant with better success and become

number 1 dormant rooted cutting and a 1 yearnumber 2 cutting. The 2 year number 1 is a morevigorous cutting and will transplant with bettersuccess and become productive quicker than thenumber 2 cutting. The rooted cutting should beproduced in a Phylloxera free nursery andcertified as virus free. Although certified virus-free vines are initially more expensive, they avoidthe higher costs of lower production and poorplant health that virus-infected vines experiencelater. These cuttings should be ordered as far inadvance as possible - usually one year prior toplanting.

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Rootstocks and PhylloxeraThe primary reason for planting rootstock-

grafted vines is the presence of phylloxera, a tinyaphid-like root louse that spends most of its lifecycle in the soil feeding on grape vine roots. Susceptible vines eventually die.

The most effective technique in managingphylloxera has been the use of tolerant or resistantrootstocks. Grafting 2 different varieties orspecies to form a plant with desired characteristicsis a technique that has been used for centuries infruit tree production and viticulture. This culturalpractice was first used to change variety, increasevigor or increase limestone tolerance withgrapevines.

It wasn't until after the great Europeanphylloxera epidemic during the decade of 1860,that the use of rootstocks increased dramatically. In France, the phylloxera epidemic had spread at arate of 12.5 miles a year and by the end of the19th century, grape phylloxera had killed morethan two-thirds of the vineyards on the continent. At that time, all of the vineyards on the Europeancontinent were planted to self-rooted Vitisvinifera. The interest to control this pest wasextremely important. Grafting the susceptiblewine varieties to the resistant American speciesworked well and became an adopted practice thatled to a chaotic period (1880-1930). Nurseriesoffered an assortment of rootstocks which causednew problems that were not previously known. Rootstocks were extensively studied in Europeand the New World for more than a century. Research after 1950 revealed that several aspectsof scion behavior such as tolerance to soil bornepests and diseases, vigor, productivity,adaptations to growing conditions, resistance tochlorosis, etc. were dependent on features of therootstock. (See tables 1-4).

In the 1850's, phylloxera was brought toCalifornia from the eastern US. In 1988,phylloxera was discovered in commercialvineyards in Washington state and in 1990 it wasdiscovered in vineyards in Oregon. BothWashington and Oregon are relatively new grapegrowing regions. Colorado is also a new grape

growing region with only 380 acres planted,however, the size of the industry or the climatedoes not make Colorado immune from phylloxera. Phylloxera has not been detected on the westernslope of Colorado and has only been observed inBaca County (1993-Kondratieff) on a nativeamerican grape species. Currently, the Coloradowine industry is 98% self-rooted. In 1995approximately 6 acres of rootstock grafted vineswere planted in Colorado. Rootstocks should beconsidered in new plantings as an insuranceagainst possible infestation.

A new strain of phylloxera called biotypeB has recently become a major problem forCalifornia growers using AXR #1 rootstocks. TheAXR #1 rootstock is susceptible to biotype Bphylloxera. California growers are spendingmillions of dollars replanting AXR #1 rootstockvineyards to resistant rootstock-grafted vines. Due to the problem California has encounteredwith AXR #1 being susceptible to phylloxerabiotype B, Colorado growers should avoidplanting on rootstocks that have Vitis viniferaparentage (see table 1). In 1992, four phylloxeraresistant rootstocks (3309C, 420 A, 101-14 and5C) were planted for study at the Orchard MesaResearch Center. These rootstocks were selectedfor their phylloxera resistance and low-to-moderate vigor. The results of this study are notcomplete and their recommendations would bepremature. Consequently, rootstockrecommendations for Colorado islimited to experience from other cool climategrape growing regions (e.g. New York,Washington, Oregon). Based on experience fromthese areas vigorous rootstocks that tend toproduce undesirable rank growth (eg. 5BB, 5C,504, 99 Richter, Kober 125 AA) should beavoided. Rank excessive growth is winter tendergrowth and rootstocks with this characteristicshould only be used in very low vigor sites(sandy, rocky well drained soils with lowfertility). Rootstocks with low to moderate vigor(eg. 3309, 101-14, 420-A) are more desirable for most Colorado sites. Rootstocks require

11

protection during the cold winter months. Routine hilling of soil 6-10 inches above the graftunion in the fall will protect enough scion tissue

to regenerate in the event of very cold trunkkilling temperatures.

Table 1. Common rootstocks listed by parentage (Morton and Jackson, 1988)

Parentage Rootstock

Riparia Riparia gloire de Montpellier (Portalis)Riparia, Berlandieri SO4, 5 A, 5 BB, 5 C, 8 B, 34 E.M., 125 AA, 225 Ru, 420 A,

157-11 C, 161-49 C, RSB 1, Cosmo 2 & Craciunel 2 & 71Riparia, Labrusca ViallaRiparia, Rupestris 3306 C, 3309 C, 101-14 Mgt, SchwarzmannRiparia, Vinifera 143 A, 143 BRupestris Rupestris du Lot (St. George)Rupestris, Berlandieri 57 R, 99 R, Prosperi Super 99 R, 110 R, 140 RU, 775 P,

779 P, 1103 P, 1447 PRupestris, Vinifera AXR 1 (ARG 1), 93-5 C ("XX"), 1202 CBerlandieri, Vinifera 41 B, 333 E.M., FercalComplex (2 species) 44-53 M, 1613 C, 1616 C, 1045 P, 196-17 Ca, 216-3 CA,

4010 Ca, Dog Ridge, Golia, Grezot 1, Harmony, Salt Creek (Ramsey), Tampa

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Table 2. Phylloxera resistance rating; based on potted vines and Italian phylloxera. 10 is absoluteresistance, 5 is tolerable resistance and 0 is completely susceptible. (from Pastena, B. 1976 Trattato diViticoltura Italiana)

Rating Rootstock

10 rotundifolia 9 riparia, berlandieri, and cordifolia8 rupestris, 779P, 420A, 41B(?)7 St George, 1103P, 140Ru, 11OR, 775P, 41B (in Palermo), 1447P6 3306C, 3309C, 225Ru, SO4, 5BB, 161-49, 157-11, 1045P, 44-535 Solonis, Jacquez4 AXR#1, several hybrid direct producers2-3 several vinifera cultivars: Tannat, Nocera, Olivetta, Carignane,

Sangiovese, Barbera, Trebbiano dorato, Sauvignon, Grecanico1 hybrid direct producers (many S.V. numbers, some Seibel)0 Vinifera and more hybrid direct producers.

Table 3. Resistance to nematodes (Meloidogyne spp.) (from Pouget and Delas, 1989)

Rootstock Variety Resistance

3309C lowGravesac low110R low161-49 low41B lowRiparia Gloire moderate420A moderateFercal moderate101-14 high140Ru high1103P highSO4 high

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Table 4. Resistance to lime-induced chlorosis; value of the Chlorosing Power Index (IPC) above whichsymptoms appear.(from Pouget and Delas, 1989)

Rootstock Variety IPC

Riparia Gloire 5 Low 101-14 10 3309C 10 Gravesac 20 110R 30 1103P 30 SO4 30 420A 40 161-49C 50 41B 60 140Ru 90 Fercal 120 High

Site PreparationPreparing the site for a vineyard is very

important and should be planned out in advance.One of the first steps in preparation is to removeall trees, stumps, rocks, wire, and even oldunusable irrigation pipe. Reluctance to removethat wonderful shade tree is often regretted laterwhen the vines planted near the shade of the treedon't grow like the vines planted in the open,unshaded field. Special soil preparation decisionslike deep ripping or weed control are best attendedto before vines are planted, especially if the use ofbig machinery is required. Perennial weeds suchas bindweed (Convulvus sp.) or even alfalfa arevery persistant and are best removed if treatedwith herbicides (i.e. glyphosate) the season beforeplanting, typically at the end of August. If asubsurface hardpan (created by equipment use or anatural impervious layer) is suspected, thevineyard should be deep ripped below that depthbefore planting when the soil is dry, typically thefirst of September. Powerful heavy machinery(D-8 cat or larger) is required for effective rippingof 45 inches or more. The ripped field willbenefit from freeze/thaw action if left uncultivatedduring the winter months. As soon as the wintermoisture subsides, disk, plow, disk, and float(level) your vineyard site for final preparation. At

this time, surveying the vineyard for roworientation and vine spacing will facilitate theplanting process. Planting holes are most oftenaugered, although in clay soils this can produce a"flower pot" effect. Holes can be made in the fallbefore planting and will weather sufficiently toprevent this. Holes augered in the spring shouldhave their sides cut away (caved in) at planting inorder to break any glazing of the hole wall. Vinescan also be planted in a V-ditch with the aid of atractor mounted V-ditcher. A very reliable butoften disliked method of planting is simple handdigging. Individual vine stakes should be placedbefore or during planting since delays in theirplacement during the training year can be costly interms of proper vine formation.

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Vineyard Development Checklist(One year in advance)

� Determine Market outlook and winery demand, and select appropriate

varieties.

� Determine physical and chemical suitability of soil (back hoe, soil test).

� Check irrigation water availability and quality.

� Check for diseases and nutritional imbalances of existing crops.

� Control perennial weeds: bindweed.

� Clear site and level the land if needed.

� Rip the soil when it is dry (August-September).

� Disc, plow, smooth soil in preparation for planting.

� Survey the vineyard site.

� Make scale drawing of the proposed new vineyard.

� Order #1 certified virus free dormant rooted cuttings from nursery.

� Install irrigation system.

� Install elk/deer fence (if necessary).

� Lay out and plant vineyard in the spring after frost hazard is past and soil

has warmed.

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Trellising/Training:There are several dozen different trellis

systems in use today. We do not attempt todiscuss them all in this grape guide. Each trellissystem is unique and has a function specific toeach situation. The handbook for canopymanagement "Sunlight into Wine" by Smart andRobinson is an excellent reference for those whoneed more information on various trellis/trainingsystems. The scope of this section is to providesome major factors to consider when selectingyour trellis and to provide some basic informationon constructing a commonly used vertical shootpositioned trellis system.

Trellising and training go hand in hand. Training is the strategic development of grapevinestructure and the trellis supports that vinestructure. The basic goal of trellising and trainingis to maximize production, facilitate culturaloperations (i.e. spraying, tillage, pruning,harvesting), improve canopy microclimate and tosupport the mechanical load of the vine.

The initial choice of a trellis system iscritical because vineyards are long term andusually trellised only once. Vineyard retrofittingor converting a vineyard to an improved trellisingsystem is possible during the dormant season butcan be very costly.

In the last 20 years trellising of grapevineshas seen considerable advances. The advanceshave been initiated by the desire to improve fruitquality, produce higher yields and increasevineyard mechanization (trimming, leaf removal,harvesting and winter pruning). These newimproved trellis systems have had the mostsignificant impact on vineyard canopymanagement. Some common features ofimproved trellis systems are; increased canopysurface area, decreased canopy density, increasedcapability for mechanization, improved yield andquality, better spray penetration, less disease(Botrytis and Powdery Mildew) and increasedwinter hardiness (more "sun" canes and less"shade" canes).

The following factors are the mostimportant considerations when selecting your

trellis system. Vineyard potential, variety vigor,and canopy spacing are the most important and toa lesser degree economic factors. Vineyardpotential would include environmental factors (i.e.temperature, topography, soil, rainfall and wind)and cultural management decisions (shootthinning, fertilization, irrigation etc.). Varietyvigor can often determine the choice of trellissystem. For example, choosing a single wiretrellis as compared to an improved multiwiredtrellis system with moveable foliage wires may besufficient for varieties with low vigor. Vines withexcess vigor (long shoots, lateral growth, andshading) may need a more extensive trellis systemsuch as a Geneva Double curtain, U-trellis or Lyresystem. The high vigor trellis systems usuallydivide the canopy to support a higher number ofbuds and thus increasing canopy surface area.

Canopy spacing is a combination of rowspacing and vine spacing. In Colorado, thedistance between rows varies from 6 to 12 feet. Equipment availability, tractor widths andcompaction has most growers planting 9 to 10 feetbetween rows. Specialized narrow vineyardequipment is not readily available in Colorado andthus 30-50 HP standard farm tractors are common. Closer row spacings (6 to 7 feet) increases soilcompaction with standard tractors. As a generalrule of thumb, row-spacings should not be plantedcloser than the height of the trellis (shading canoccur).

Vine spacing, the distance between vineswithin the vine row is a combination of vinegenetic vigor, soil capability and climatic factors. Vineyards in Colorado commonly have vinespacings between 4 and 8 feet. Vineyard sites thatare fertile and productive need larger distancesbetween vines. Soils in many vineyards ofwestern Colorado substantially vary within thevineyard and may require vine spacingadjustments within a 200 foot vine row. Soilanalysis and visual inspections before planting canassist in these decisions. Genetic vigor variationamong varieties also plays an important role withvine spacing. Site specific vigor i.e. how well a

16

particular variety grows in that specificsite/situation would be ideal, but unfortunatelyonly general information exists at this time. Genetically vigorous varieties typically requiremore distance between vines than less vigorousvarieties. Vineyards in cooler sites generally haveless growth (vigor) than warmer sites andtherefore narrower spacings are more suitable. Growers in Colorado who have ignored soil orgenetic vigor differences have had trouble trainingtheir vines to maximum production levels becauseof overcrowding, too dense of canopy, poor spraypenetration and training/pruning confusion.

The Vertical Shoot Positioned Trellis(VSP)

The VSP trellis is a good canopymanagement system for low to moderatelyvigorous vines. The VSP works well in Coloradoand the one described here is currently used at theOMRC. The VSP trellis contains either fixed ormoveable pairs of foliage wires that enable thegrower to form a narrow vertical canopy (seefigure 6). The VSP trellis system can be usedwith either cane-pruned vines or spur-prunedvines on unilateral or bilateral cordons. Shootsare kept between the foliage wires by lifting themoveable foliage wires and attaching them atsuccessive heights on either side of the line postsand hand tucking. This procedure is usuallyrequired 2 to 3 times during the period of activeshoot growth. The shoots are retained in a narrow(5 to 7 inch wide) vertical curtain. Up to 3 pairsof foliage wires can be used but 1 or 2 pairs ismore common. The fruiting wire is normally at40 inches with the first pair of foliage catch wires10-12 inches above and the second pair 10-12inches above that. The single catch wirepositioned at the top of the trellis also serves as asupport for bird netting. The entire canopy heightof approximately 40 inches contains plenty of leafarea for fruit maturation. The VSP trellisdescribed in figure 6 uses 4 inch by 8 foot CCAtreated pine line posts driven 2 feet and spacedevery 30-40 feet. End bracing posts are also CCAtreated pine that measure 4-5 inches by 10 feet

and are driven 4 feet.Posts: Lodgepole pine and native juniper

posts are frequently used in Colorado vineyards. Pine posts are the most common and are typicallypressure treated with a mixture of copper,chromium and arsenic salts (CCA). Once boundin the wood, CCA treatment becomes insolubleand non-toxic to vines. Juniper posts containnatural preservatives and are not treated. Anadvantage of pine posts is the ability to be able todrive them into the soil with a hydraulic powerdriver. Driving the posts with the narrow enddown compresses the soil and increases poststability. Driving the posts is also moreeconomical than boring a hole and hand tamping.The importance of a stake per vine cannot be overstressed. When vineyard construction begins donot neglect a stake per vine. Individual vinestakes vary in size, material (metal, wood, plastic,bamboo) and strength. Select a stake that will lastfor a good 15-20 years. These stakes will aid theretraining efforts and help stabilize and protect thevine if mechanical weed control is used.

Wire: Trellis wire usually ranges between10 and 13 gauge. Twelve and a half gauge hightensile wire is common and normally wound on100 pound spools that contain 4,000 linear feet. A"spinning jenny", a device used to unwind thewire painlessly in the field is a must for any trellisconstruction. The wire is fastened to line postswith 1.5-2 inch barbed staples, and in the case ofmoveable foliage wires, one legged J-nails areused. Trellis wire is tightened with a standardwire stretcher and attached to the end posts withpatented wire fasteners. These fasteners are small1/2 inch leaded sleeves that hold two wirestogether when crimped. Temperature effects,wind loads and fruit loads put a strain on wiresand they occasionally need tightened. Simpleratchet type tensioners do a fine job and areusually available where wire is purchased.Excessively tensioned wires can adversely affectyour entire end bracing assembly.

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Figure 7. "H-Brace" trellis brace assembly. Vine planting within the end brace assembly is possible.

The End Brace Assembly: Bracing theend of your trellis is the most importantcomponent of the trellis system. Improper bracingcan lead to failure and costly repairs. Trellisfailures can be prevented by avoiding thefollowing common mistakes: Inserting andbracing posts into deep-ripped trenches, excessivetensioning of the trellis wires, tractor/implementabuse and inserting end bracing posts to depthsless than 3 feet. Figures 7 and 8 describes twoend bracing assemblies.

The main difference between the H-braceand the tie-back is planting efficiency and greaterprotection. The H-brace enables vine planting to the end of the vineyard row without vine trainingmodifications. The tie-back assembly is equally asstrong as the H-brace, has lower up front costs butdoes not allow adequate training space forefficient vine management. Tie-back or "deadman" anchoring posts are more prone to tractorblight than the H-brace assembly.

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Figure 8. "Tie-back" trellis brace assembly. No vine planting within this type of end brace assembly.

Planting - The First YearThe goal of the planting season is to es-

tablish a strong root system at the proper depth. This is accomplished by careful attention to a fewmajor points.

The fully dormant rooted cuttings shouldhave a substantial root system and reasonable topgrowth. They should be long enough so that twobuds of the previous season's growth are aboveground and the bulk of the roots begin at a depthof 12 to 14 inches (see Figure 6). The rootingdepth is critical; shallower roots will respond tooquickly to winter and spring soil temperaturechanges and lead to winter killing or frostdamage. Uniform rooting depth also is veryimportant for controlling drought stress and

properly maturing the crop for consistent winequality.

The cuttings must be carefully protectedbefore and during planting to avoid drying andoverheating. This is even more critical if thevines have started to grow due to overly warmstorage at some point. Generally it is best toavoid the coldest winter temperatures. Springplanting (April-May) is the best time to plant inColorado. In any case the vines should beplanted before high temperatures occur. Cuttingsshould be stored in a cool place (40oF) and keptmoist until planting can begin.

The roots can be lightly pruned to fit thesize of the hole and to remove any dead ordecayed tissue (Figure 9C). At planting, the

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Figure 9. Grape propagation plant materials: A) Grape cutting (14 to 16 inches) with sloping cut at tip end to ensureproper orientation. B) One-year-old own-rooted cutting as received from nursery with some shoot and root growth. C)Properly planted rooted cutting; note that dead or damaged roots should be removed and the remaining roots prevented frombunching. Two buds [b] are left from nursery growth.

cuttings should be set in water (i.e., in tubs ordrums) until they are actually placed in the hole,but should not be kept in water more than oneday. The vines should be set an inch or two belowthe desired 13 to 14-inch depth, then add a fewinches of fine soil and then gently tug the vine upto arrange the roots in a slight downwardorientation. Any bunching or twisting of the rootsshould be avoided to prevent the vine's selfstrangulation as it grows.

The vines should be irrigated immediately

after planting, making sure that water reaches theroots. Failure to deliver water at planting andover the first few months of a vine's lifecommonly results in an inadequately preparedvineyard and leads to poor growth andestablishment.

Throughout the remainder of the firstgrowing season, maximum growth of the youngvine should be encouraged. This can be done byproviding a balance between the water and oxygenneeds of the developing root system; over- and

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underwatering should be avoided. The waterstatus of the soil from which the limited rootsystem actually is drawing can be determined withsoil probes or with tensiometers placed at theproper location. Vines do not use a great deal ofwater, but irrigations must be long enough for water to reach the deep roots. Once the vine isplanted, an irrigation schedule should beestablished. Surface irrigation every 2 weeks (6-8hour sets) is very effective for the establishmentyear. Drip irrigation of 15 gallons per vine perweek is also recommended for the establishmentyear. These recommendations are for deep clayloam soils. More frequent irrigations may benecessary on sandy well drained soils.

Optimum growth requires the removal ofcompetitive weeds. Generally, bindweed andalfalfa are the biggest problems and should beremoved by mechanical or chemical means withinat least a 3 foot radius of the vine.

The vine's growth and winter hardinesswill be compromised if powdery mildew is notcontrolled in mildew-susceptible varieties --especially the Vitis vinifera varieties. Powderymildew occurs in all grape growing areas ofColorado and applications of mildew-effectivefungicides at two to three week intervals fromJune through August are wise preventativemeasures (see Disease Management, Section IV).During the initial stages of acclimation, (whengreen shoots begin to turn tan in color) the vinesare allowed to dry to encourage good woodformation toward the base of the shoots. Anirrigation after leaf fall is encouraged to preventwinter desiccation of the soil and subsequent rootinjury. Mulching or throwing up a few inches ofsoil over the crown of the vine can provideprotection against winter injury. The vine is bestpruned in the spring (March) to leave only oneshoot with two buds (see Figure 10B) and ifgrowth has been encouraged, it now has a rootsystem that can support vigorous growth in themost crucial year of the vineyard's life - thetraining year.

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Figure 10. A) Growth at the end of the planting season. B) Above ground portion of vine following first pruning; note twobuds [b] from first year vineyard growth are retained.

What About Grow TubesThe grow tubes or plastic shelters have

become a very popular method for training newlyplanted vines in California and other grapegrowing regions. Colorado has also joined thetrend with several growers beginning to use thetubes in 1995. The grow tubes are plastic sheltersavailable in various colors (white, blue, green,etc.) and sizes. Typical stock sizes are from 24 to44 inches high with diameters of 2-3/4 inches to4-1/2 inches. The grow tubes have been reportedto enhance growth, reduce training costs andprotect vines from chemical sprays and rodents. Suppliers recommend the grow tube to be placedover the young vine at planting. They alsorecommend the grow tube be pressed into the soil2 inches and tied to the grape stake or wire for

stability and micro climate maintenance.Growers in Washington state find the

plastic shelter useful, especially with younginterplants that are struggling. Recentunpublished work at UC Fresno, Californiasuggest the narrow tubes (less than 3-1/2")increase temperatures to extreme levels causingfoliar burning. Colorado growers have had goodand bad experiences with the plastic shelters. Some Colorado growers excessively burnt theirvines with grow tubes and they claim late plantingto be the major cause. Other growers had positiveexperiences, claiming first year growth was betterthan they had ever seen. Removal of the tubeswas a topic of confusion. Some growers removedthe tubes when burning was evident while others

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waited until early fall. Growers who used thetubes were planing on single trunk, not doubletrunk training. Double trunk training may be morechallenging with grow tubes. Most growers feltthe grow tubes were beneficial but expensive. Grow tubes normally range in price from $.40 to$1.40 each plus the cost of installation andremoval.

It appears that grow tubes will be used by somegrowers in Colorado regardless of the pros andcons. The tubes are expensive and moreexperience under Colorado conditions is needed. Correct grow tube use may be a cultural practicethat can favor early vine development andenhance vine establishment; however, incorrectuse could be detrimental.

The Training YearPerhaps because there is no crop, grape

growers tend to give insufficient attention to thenew vines during their second year. The cost ofthis mistake will be felt throughout the expected30 to 40 year life of the vineyard. The goal of thetraining year is to establish the framework of thevine so that future pruning will be efficient andcrops of the future will be properly supported. Although the vine looks like it did at the time

of planting, the carbohydrates stored in itsexpanded root system have prepared it withenough energy to develop a trunk and cordonarms or canes. If the vine's environment is keptentirely weed free and the steps of training arecarried out in a timely and accurate manner, thevine will reach training height and be ready toproduce a modest crop the following year.

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Figure 11. Grapevine training during the second season. A) Early growth (6 inches) before choosing a shoot to train. B)Strong, well-positioned shoot tied after removal of other shoots. C) Shoot tied to form a straight trunk -- growth is 18 to 24inches above lower wire; it will be topped at the node [n] just above that wire. Note that all lateral side shoots on the lowertwo-thirds of the trunk have been removed, directing growth to the trunk. D) Growth at the end of the second season inwhich the trunk and laterals were established. E) Vine pruned in March, retaining three two-bud spurs [s]. Short, lateralcanes are often retained on very vigorous vines.

A shoot is selected when it is about 6inches long and all the other side shoots areremoved (see Figure 11C). Remove only thelateral side shoots at each leaf axil, not the leaves. The chosen shoot is carefully tied to a support asit grows so that a straight trunk is formed. A fiveto six year old vine will be strong enough tosupport much of its own weight if its trunk isstraight. If it is not straight, the vine will neverhelp bear the load and will put inordinate strain onthe trellis system with crop weight and windaction. The system in which a permanent stake isplaced at each vine requires frequent tying tomake a straight trunk. Having a good permanent

stake at each vine is very handy for any futureretraining needs. Obviously, the training supportmust be in place before growth begins the secondseason.

As the shoot grows, it should be firmlytied (without crushing or breaking the tendertissue) a few inches behind its growing tip atapproximate 6-10 inch intervals. This mayrequire a tie every five to eight days if the vine isgrowing well. By late spring, the vine will begrowing as fast as one inch per day. The best wayto tie is with commercially available ties orflexible tying tape.

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Figure 12. Second year training options.

Young shoots with less than 15 inches ofgrowthare very susceptible to breakage. Careshould be taken when tying and forming the trunk. Each vine must be visited every week and newshoots or buds arising from the crown of the trunkmust be cut off and laterals removed up to the"head" training height (lower wire). All fruitinflorescences are removed but the leaves on thenewly formed trunk should be retained tostrengthen it.

Three common second year trainingoptions are described above (Figure 12). Previouseditions of this guide suggest that once the canehas grown 18 to 24 inches above head trainingheight, it should be cut back to the point at whichthe vine will be headed (See figure 11). Thisforces laterals in the axils just below the cut. Thismethod does work however, lateral spur growth

development for cordon trained vines is delayed. A method that gives a 2-3 week advantage oncordon arm and lateral spur development is eitheroption 1 or option 3. Option 2 works well for theclassic head trained cane pruned vine. Option 1and option 3 are more appropriate for cordontrained vines. Option 1 is often referred to as asingle trunk unilateral cordon. Option 3 isreferred to as a double trunk bilateral cordon. Option 1 would be used in high density vineyards(4 feet between vines) with low vigor vines. Option 3 is better adapted for cold climates. Mostviticulture areas of Colorado occasionallyexperience temperatures cold enough to causetrunk injury. The double trunk system (option 3)provides for some additional protection. Frequently, when cold temperatures aredamaging, one of the two trunks remain uninjured

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and thus retains a partial crop. The advantage ofoption 3 is quicker lateral spur development andpotential retention of a partial crop as a result ofcold injury. Nearly all vinifera vineyards inColorado have multiple trunks. Multiple trunktraining is a cold climate viticulture managementtool (see Retraining Winter Damaged vines) thatis an effective method of controlling vine vigor oninjured vines with "out of balance" shoot to rootratios.

During the training season it is againimportant that the vines have adequate wateravailable through May, June, July and August. Depending on the soil type and irrigation system,water should be withheld in late August or earlySeptember to encourage the formation of woodand the cessation of succulent growth. Often, fruitclusters can occur on the two nodes left from theprevious year. These may aid in slowingvegetative growth in the late season. If the vine isnot growing well by midsummer, the clustersshould be removed to minimize the growthdifference from the more vigorous vines.

Pest and disease control also is crucialduring the training year (see Pest Management /Control, Section IV). Cut worms and Lygus bugsmay feed on the growing point of the vine. Although the vine will regrow from a lateral if theapex is destroyed, valuable time and a straighttrunk will be lost. At any sign of cutwormdamage, carbaryl baits can be sprinkled aroundeach vine. Lygus injury is best halted by applyingan insecticide such as diazinon.

Powdery mildew must be controlledduring the training year. A main shoot heavilyscarred with mildew has a much smaller chance ofsurviving the next winter. The normal mildewprogram should be followed (see pages 47-51)and continued later in the summer since residueon the fruit is not a problem. Again, a post-leaffall irrigation is desirable.

Pruning after the training year should bestarted after the coldest part of winter and, ifpossible, during March when all winter damagecan be assessed.

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Figure 13. Vine at conclusion of third season growth on a two wire trellis.

The Third YearThe vineyard should produce a small crop

in the third year, but generally it’s best not to relyon it in for financial planning. The quantity willbe small, and the pattern of its maturation will beunlike that of a more mature vine. Most of thecare for a third year vine is like that for a maturevineyard with the following points of emphasis. Itmay be wise to tie shoots to the wind-catch wirewhen they are around 24 inches long. Windbreakage is more significant when there are fewershoots. The use of moveable catch wires forcanopy manipulation has provided excellent shootbreakage control, sunlight penetration and aircirculation. Removing suckers is alwaysimportant, but is required to a greater degree witha young vine. During the third year, periodically

break off the shoots on the lower two thirds of thetrunk to encourage better growth in the head area.Grapes from three year vines can ripen earlierthan the characteristic time for a mature vine andacid content can be lower. In order to get the bestuse of the crop, carefully monitor acid content toobtain the best possible sugar/acid balance. Donot judge future wine quality based on fruit from the third or fourth year grapes. It will probably belighter and not develop the full character that ispresent in older, more mature vines.

Pruning after the third year emphasizesboth selection of two strong canes which will fillas much of the trellis wire as possible and selection of well-positioned renewal spurs(Figure 14).

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Figure 14. Vine pruned to two canes [c] and three replacement spurs [s] before start of fourth season.

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Maintaining a Vineyard

In this section, the various components ofvineyard management will be discussed separately. Optimum management is based on a completeunderstanding of your vineyard site.

and the vines needs. These discussions areintended to emphasize the special concerns of highaltitude arid viticulture.

Water ManagementWine grape yield and quality are

determined by climate, soil and culturalmanagement practices including irrigation. Poorirrigation management can result in a waterstressed or over vigorous condition resulting inunbalanced growth, reduced yields and inferiorfruit quality.

For practical purposes, rain can be ignoredas an input to the water status of a vineyard inColorado. Rains do occur, but almost never wetthe soil to a depth that can benefit a properlyplanted grapevine. Thus, the water supplied byirrigation not only keeps the vines alive, but alsois the major tool the viticulturist has to optimizewinter hardiness and wine quality.

Grape vine water stress can occur if thesupply of water to the roots is less than theevaporative demand. The cause for the stress maybe low available soil moisture, high evaporativedemand conditions, unbalanced shoot/rootsystems, a poorly developed root system, high saltlevels or a combination of these. Unlike tomatoesor squash, immediate signs of current seasonwater stress are not clearly visible withgrapevines. Symptoms are typically observed afterrepeated episodes of water stress, which causereduced shoot and fruit development.

During the early part of the season (May-August) the vines should be given a good supplyof water to promote growth. Humidities are verylow in Colorado so water is transpired veryrapidly. Few growers can precisely control theamount of water they apply and, even if they can,it is better to calibrate the irrigation through somedirect measure of the soil water status in therooting zone. Grape vines do not require as much

water as do many tree fruits, but this should not betaken to an extreme. As a point of reference, on adeep, fairly heavy soil, three to five 12-hourfurrow irrigations are sufficient for mature vinesbetween May and September. The last irrigationis timed to allow the vines to experience mildstress that encourages a switch from rapid,vegetative growth to the maturation of the cropand the wood on the canes. If drip irrigation isused, a rate of 12-15 gallons per vine per week formature vines is typically sufficient. With dripirrigation, reducing the rate per vine per week by40-50% approximately two to three weeks beforeharvest will also encourage fruit and shootmaturation. For example, an irrigation rate of 14gallons per vine per week would be reduced(40%) to 8.4 gallons two to three weeks beforeharvest. It is, however, very easy to overstressvines under Colorado conditions; in this case thecrop will stop maturing and the canes also will beless winter hardy. Finding the middle groundbetween excess growth and excess stress is themain challenge of learning to grow grapes in eachindividual vineyard. Parts of a given vineyardmay have different requirements. As a startingpoint, the middle of August is an approximatetime to stop irrigating many Colorado soils so thatthey dry to some degree through September. Ifthe cut-off is too early, one may see the loss ofleaves and a marked slowing of sugaraccumulation by the fruit. If the cut-off has beentoo late, the basal portions of the canes may fail tobecome brown and woody and fruit may retainvery high acidity (some varieties will retain highacidities under any circumstances).

Occasionally, winters are sufficiently dry

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in Colorado to cause the killing of roots throughdesiccation. To prevent this type of winterkilling, it is best to restore the water in the soilwith a late irrigation. This is best timed after thefirst frost so that there is no chance of shifting thevines back into a vegetative pattern. Sometimesthe irrigation

system is closed down before a frost; in this casestill irrigate on the last day practical as it generallyis too cool for the vines to become active again. Ifthe crop is still present, a decline in both sugarand acid may occur through dilution in followingirrigation; however, the effect may only last aweek or so.

Protection Against Winter InjuryThere are several ways that vines may be

damaged in the winter. Two that have beenmentioned are best prevented through watermanagement. The killing of green tissues at thefirst frost is best prevented by encouraginghardening off of the canes. The killing of roots orabove ground tissues through winter desiccation isbest prevented by a late irrigation to recharge thesoil.

The killing of buds or canes and eventrunks by very low temperatures is minimized bythe same steps described above, but is less easilycontrolled. As mentioned earlier, avoid areassubject to sudden temperature drops and pick siteswith good cold air drainage in order to minimizethis problem. One way to prevent winter damageby extreme cold is to take the vines off the trellisand bury them under 6 inches or so of soil. Thispractice is very expensive and is not common.

A final type of winter damage may be theone that causes more damage than any other typein Colorado. It is termed "false spring damage". The parts of Colorado protected from the coldesttemperatures and rapid changes of winter temper-ature sometimes experience winter periods of verymild temperature. This can lead to soil warmingand reduce vine hardiness. The best cure forprotection against winter injury is to grow ahealthy vine. Vines that are stressed by poorcultural practices are vulnerable to winter injury.

In Colorado, the bright winter days warmthe dark trunks of many vines well above airtemperature. This can result in damage when thetemperature suddenly declines at sunset. As withfruit trees, painting the trunk with white latexpaint can help minimize this. Training the trunkon the north or northeast side of a stake alsoaccomplishes the same goal of preventing heatloading.

Frost Protection and Damage Treatment

In Colorado, grapes actually are lesssubject to spring frost damage than in manyimportant grape growing regions of the world. They also are in less danger than the traditionalfruit crops of the area. This is because they tendto break bud two weeks later than peaches, whichreduces the time and risk of frost injury. Windmachines are the method of choice to frost-protecta large commercial scale vineyard.

Heaters: University of California tests show that,for hard frosts, adding a small number of heaterscan provide more warming than use of windmachines without heat. For example, 8 to 12heaters per acre to support a wind machine canprovide an additional 1-1/2 or 2oF more than withthe wind machine alone, because the windmachine distributes heat that otherwise would ispartly lost by updraft from the heaters.

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Wind Machines: The theory behind windmachines for frost protection is based on theassumption that temperatures in and abovevineyards are assumed to increase with heightduring nights with little cloud cover and lightsurface winds. The purpose of a wind machine isto mix air vertically and transport it horizontallydisplacing cold air at vine height with warmer airbrought down from above. Effective operation ofwind machines requires that a sufficiently strongtemperature inversion exists. Site specificinversions can be determined by placing onethermometer at fruit height and the other at the topof the wind machine. Late spring frost protectionshould begin when air temperature is 31oF andshould be terminated when the air temperatureoutside the treated area is at least 32oF. Windmachine protection in early spring (just before budswell) may also be beneficial. Vines are in atransitional stage at this time and lose their mid-winter hardiness and become susceptible to injurywith temperatures in the low to mid-twenties.

Delayed Pruning: Pruning grapevines inlate February or March (delayed pruning) is acultural practice normally recommended forColorado conditions. The objective of delayedpruning is to permit some compensation in theevent of bud or cane/trunk injury duringDecember, January and February. Thirty years ofweather data recorded at the Orchard MesaResearch Center in Grand Junction indicate severearctic cold spells (0oF or lower) occur before the15th of February. If pruning can be delayed untilafter mid February, uninjured tissue (bud, cane)may be more available than if pruning occurs inthe dead of winter. A decision to delay pruningmust be factored in your overall managementstrategies because with large acreage it is simplynot possible to wait until March and hope to finishbefore bud-break. An alternative is to prune thehardiest varieties first and delay pruning with theleast hardy varieties.

Rough pruning, (removal of poorlypositioned canes and rank growth) in January andFebruary followed up by quicker less congestedpruning during normal spring pruning season is a

frequently used management strategy forefficiency. Regardless of whether you roughprune or not, pruning should be completed beforebud break which usually occurs the 3rd week inApril for the Mesa County area.

Late Pruning: Late pruning (after thebuds on the apical parts of the canes have startedto grow) delays the leafing out of the buds on theretained spurs and can protect vines from earlyfrosts. This delay may vary from three days totwo weeks, depending on temperature. When it isvery warm, the delay is short; when it is cold, thedelay is longer. Shoots that grow mainly on theapical portions of the canes can be allowed togrow 3 or 4 inches without injuring the basal budsor vine in general. In large vineyards, delayedpruning may present labor problems, especiallyduring seasons when vines burst into rapidgrowth. If shoots should grow considerably morethan 3 or 4 inches before pruning, the vines maybe weakened and the crop reduced.

Treatment of Frosted Vines: Treatmentof frosted vines requires patience. Frost damageto grapevines becomes apparent within a fewhours, but the degree of injury to clusters cannotaccurately be determined until after fruit set. Inmany frosted vineyards it is best to do nothing,but in others shoot removal may be beneficial.

When vines are frozen, look to thesecondary or tertiary buds or dormant latent buds. Some crop can be expected from varieties wherethese buds are fruitful, even if shoots that developfrom the primary bud are frozen. Frozen shootsshould be removed immediately after a freeze toenhance growth from secondary growing points. When growth does occur, secondary and tertiarybuds usually initiate shoot growth in about twoweeks. Secondary growth is best if shoots are lessthan 6 inches long when frozen.

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PruningA complete discussion of pruning

philosophy is not possible here. However, theessential goal of pruning is to match theproduction of a vine with its growth potential. Pruning is the removal of living shoots, canes,leaves and other vegetative parts of the vine. Itdoes not include removal of flowers or fruit. Thepurpose of dormant pruning is to balance the leafsurface area with the capacity of the vine toproduce a mature crop. The purpose of summerpruning is to thin out (remove shoots) and/or toreduce shoot length for increased light and airexposure.

Pruning in Colorado should begin inMarch. Thirty years of weather data at OrchardMesa Research Center indicate the severe coldtemperatures of December, January and Februarywill be over by March. The threat of coldtemperatures (below 0oF) is minimal and anywinter damage can be assessed and pruningadjustments made (see Retraining WinterDamaged Vines). Pruning should be completebefore bud swell. If pruning occurs during budswell, crop loss can occur by physically rubbingoff the tender buds when removing unwantedcanes. The actual removal of the "unwanted"pruned canes can be quite abrasive to the"wanted" remaining buds. Extra care should beused.

Pruning Intentions:1. To establish and maintain the vine in a form

that will facilitate vineyard management.2. To produce fruit of a desired quality.3. To select nodes that are fruitful.4. To regulate the number of shoots/ clusters.5. To regulate the vegetative growth of the vine.

In Colorado the two most commonpruning systems are: A) Cordon trained, spurpruned and B) Head trained, cane pruned.

A. Cordon training/spur pruning: Cordon trained vines currently represent morethan 50% of the Colorado industry. Onceestablished, a cordon trained vine is much easierto prune than cane pruning. Less decision making

is needed when pruning, i.e. It is easier to seewhat to cut out. Cordon training works well witha vertical shoot position trellis system. Excellentspray penetration and sunlight exposure are someof the benefits of cordon pruned vines trained to avertical shoot positioned trellis. A cordon trainedvine will have permanent cordons attached to thehead wire. Cordons are simply modifiedhorizontal trunks with vertical spurs. Spursprovide fruiting and shoot renewal functions. Figure 12 theoretically demonstrates the second orthird year process of cordon training an ideal vine. The goal of second year training is to form thetwo cordon arms and if good growth occurs,develop vertical shoots from those cordon arms. The vertical shoots will be the fruiting wood forthe next season. If an arm does not extendhalfway to the next vine, a terminal (apical) bud isallowed to form a shoot which is trained as anextension of the arm.

One of the most critical operations tocordon training is to remove all shoots growingfrom the underside of the new cordon arm. Thisprocedure directs the remaining growth uprightand enables adequate spacing between spurs(typically 4-6 inches). As the shoots grow, tuckthem between the double catch wires to maintainthe vertical canopy. This procedure is importantand must be done on a timely basis to helpstabilize the arm and prevent it from twistingunder the weight of the shoots and prevent winddamage.

Pruning an uninjured cordon trained vineis straight forward. To prune the vine, remove theshoots that grew from the cordon arms, leavingshort (2-3 bud) vertical spurs spaced 4-6 inchesevenly along the upper side of the cordon. Retainenough buds to balance the vigor of the vine. Amoderately vigorous vine such as Chardonnaywould typically have a range of 28 to 40 buds,depending on soil and site conditions.

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Figure 15. Cordon training, the second or third growing season depending on vine vigor.

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The spur renewal process over the yearsbuilds short arms at each growing point along thecordon. These short arms should be replaced witha new shoot arising at the base once the short armsreach 3-5 inches in length.

B. Head trained, cane pruning: The buds oncanes that grew in the previous season are thesource of fruiting shoots. Each shoot will producetwo to three clusters. The level of vigor onmature vines in Colorado usually warrants leavingtwo canes and two to three replacement spurs; thismeans that approximately 40 to 60 buds areretained. Figures 16 and 17 demonstrate a headtrained cane pruned vine.

The canes that are kept are of medium thickness,with neither short nor long spaces (internodes)between buds. The canes chosen are thosepositioned 4 to 8 inches below the wire. Thesenew canes will be trained and tied to the wire. Ifpart of the cane is allowed to be higher than therest, it may result in a failure of the low buds todevelop. The canes are also selected to fill theentire trellis system. In the case of a vigorousvine, two canes are wrapped together on the lowerwire. The upper (wind-catch) wire is present onlyto allow the young shoots to have support in orderto prevent "rolling" of the cane in the wind. Renewal spurs are chosen so that the canes theyproduce from their two to three buds will be

Figure 16. Head trained,cane pruned mature vine showing growth at the end of the fourth season.

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in desirable positions to form the canes to be keptin the following season. Over the years, the headof the vine is kept in the same spot - around 4 to 6inches below the lower wire. The specialconsiderations for pruning in Colorado mainlyconcern winter damage. If pruning can be delayeduntil late March and April, it often is possible toidentify canes that have died and to retain livecanes instead. However, if the vine is damaged,all above ground parts often are uniformlyaffected. Live canes will have a moist, brightgreen color when scraped with knife. Often, thesmall diameter

portions of a shoot are brown and dead while thethicker basal portion is healthy. The opposite isnever true. Sometimes, the color of scraped canesis ambiguous -- neither green nor distinctlybrown. If no bright green canes can be found, oneshould prune the vine normally because it isdifficult to predict whether it will grow normallyor require retraining from ground level. Extremely low temperatures can kill buds withoutkilling canes, and it is a good practice to cut intobuds at random before pruning to determine thelevel of damage present and to leave additionalbuds if necessary.

Figure 17. Head trained, cane pruned mature fourth season vine (start of fifth season).

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Bleeding:Near the end of winter or the beginning of

spring the vine may bleed after being pruned. Bleeding is the exudation of sap from cut canesand a phenomenon that has no reported harmfuleffects on the vine. The sap exudate comes fromthe cut ends of the vessels of the xylem tissues(water and mineral conducting pipelines). Bleeding may occur at any time during activegrowth if a major portion of the top growth of thevine is removed. Heavy bleeding is mostnoticeable when vines are pruned at bud swell orlater. Winkler reported as much as 5 gallons ofsap exudate was recovered from individual vineswhen new cuts were made every other day. Themajor contents of sap exudate is water, sugars,mineral nutrients, solutes and the plant hormonescytokinin and gibberellin. The significance ofthese hormones and other compounds is notknown. This bleeding condition depends on theactivity of living root cells. The time of canebleeding in the spring coincides with renewal rootactivity and or growth. Vine root growth initiateswhen soil temperatures attain 48oF.

In Colorado, we observe minimal bleedingof vines pruned during mid-dormancy when rootactivity is non-existent. Drying or suberization ofthe cut xylem vessels may occur during this timeof dormancy when root activity is low and whenxylem vessel water movement is minimal. Innormal years, bleeding will not occur if you pruneyour vines the first two weeks in March. Soil andair temperatures in the fruit growing districts ofwestern Colorado at this time are still cool enoughto hinder renewed root activity.

Retraining Winter Damaged VinesUnless extreme deep ground freezing

occurs, a winter damaged vine will regrow frombelow ground level. Essentially, the idea ofretraining is the same as in the original training interms of the need to tie a shoot frequently to asupport to form a straight trunk. The differencewith an older vine is that the root system willsupport extremely vigorous regrowth. Canes thatgrow very rapidly tend to be winter tender and

may be killed the next year. See figures 18 and19.

Steps to retrain winter damaged vinesthat are self-rooted: If you suspect your vineshave been winter injured, make an actual tissueassessment. To help identify injured tissue, use arazor blade and cut horizontally through buds. Buds that are brown or black (not green) aretypically injured. Using a knife or sharp pruningshears, scrape through the bark and into phloemand cambium tissue (typically 1/8 inch deep inenough). Cane tissue that is injured will generallybe brown. All live tissue will be moist. Occasionally, trunk tissue is damaged from coldair that stratified in a layer near the ground andcane tissue is injured. As the vine begins to growin the spring and all carbohydrate reserves areused up, the canes and buds begin to desiccatebecause of trunk injury below. Injured trunktissue will have a similar dark brown oxidizedappearance but you may have to scrape (cut)through several layers of bark to expose livetissue. Live trunk tissue will have more of a light-green to white-cream colored appearance ratherthan the definite green color of live cane tissue.

Once an overall assessment has been madeand injury is evident, retraining must begin withremoval of injured tissue. If trunks and canes arepartially injured and show signs of "weak life", itis generally more productive to remove theseweak tissues. Helping the vine decide where toput its energy by removing injured weak tissuewill lead to quicker vine recovery and moreefficient (labor savings) retraining decisions.

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Figure 18. Retraining winter damaged vines. Select and tie shoots for the development of a multiple trunk.

Healthy vines that have been in the groundfor 2 years or more that have been injured toground level can benefit by incorpo-rating amultiple trunk system. A multiple trunk trainingsystem will help balance the root/shoot ratio andreduce "bull" canes and the unwanted "winter kill"cycle. Vigorous "bull" canes are winter tender canes and should not be selected forretraining. Shoots that are pencil size in diameterand have internode lengths of 2.5 to 4 inches arepreferred. Dividing the growth will help control

vigor and depending on variety and age, theremay be a need for 2-6 trunks the first retrainingyear. The following year, half of those trunksmay be removed and eventually one or two trunkswill be all that is needed to balance the root/shootratio. It is the first and second growing seasonsafter winter injury that controlling vigor is vital.

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Figure 19. Retraining winter damaged vines. Dividing growth with multiple trunks will help control vigor and avoid the"winter kill cycle."

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Management practices that minimize winter injury1. Site selection: Having the land and deciding to

grow grapes on it is not site selection. Avoidplanting grapes in valleys or low lying areas. Look for a site that has good air and waterdrainage, preferably >5% slope.

2. Varieties: Diversify, avoid planting the entirevineyard to winter tender varieties.

3. Cultural management: Cultural decisions thathelp prepare the vine for winter or "hardenoff" the vine should be carefully incorporated. Decisions that favor vigor control enhancevine hardiness. When irrigating, alwaysinclude a dry down period (especially in deepheavy soils). This dry down time provides a

slowing down or stopping of shoot growth whichhelps the vine initiate fall acclimation responses(lignification of tissues). Always apply a late fallirrigation to prevent mid-winter desiccation. Trellis modification that encourages uprightcanopy development or split canopies favorsunlight penetration which increases thedevelopment of "sun canes" rather than "shadecanes". Sun canes develop fruitful buds andhardier bud and cane tissues.

Shoot Tying and SuckeringAs young shoots reach above the second

wire in spring, it is a good practice to tie two tothree of the shoots of each cane to that wire tostabilize the whole cane. This prevents it fromrolling in the wind later in the season andexposing the fruit to sunburning. The shoots mayattach to the wire by tendrils, but not withsufficient support in windy sites. For this tyingprocess the tape guns and temporary stapled tapementioned before are ideal since they must beremoved at the next pruning. Two or three pairsof moveable catch wires can keep shoot tying to

a minimum and allow for excellent sunlightexposure and air circulation. Suckers (shootsappearing at ground level or on the lower 2/3 ofthe trunk) should be removed while green andeasily broken off. This will be necessary duringmost seasons and can be done while passingthrough the vineyard to tie shoots. Suckerremoval channels more energy into the fruit andfacilitates many other maintenance activities. If asystemic herbicide such as Roundup is to be used,it is critical that all green tissue near the ground beremoved.

Shoot ThinningFor maximum air and sun exposure of the

fruit and shoots, shoot thinning may be necessary. Shoot thinning is the removal of unwanted shoots. Vines typically grow more shoots than the nodesleft at winter pruning. These extra shoots developfrom buds at the base of the spurs or out of oldwood and often are not fruitful. In Colorado, it isnot uncommon to retain some of these shoots torenew growth from winter injured spurs/buds thatnever developed. Shoot thinning on moderatelyvigorous vines is typically started when newgrowth has reached about 15 inches and can

continue until soon after set. New shootsmay be forced from buds on the cordon orhead of the wire if shoot thinning is carriedout too early. If shoot thinning occurs toolate, the energy used to develop the shoots tobe removed is lost and the redirected energyis of less benefit to the shoots in moredesirable locations. Vines are commonlythinned along the cordon wire so that theyare evenly spaced at a distance of 3 to 5inches. In Australia, vines are typicallyshoot shoot thinned to about 15 shoots permeter (5 shoots per foot).

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Leaf RemovalLeaf removal in the fruit zone can improve

fruit composition, spray penetration, enhance fruitcolor and reduce disease by increasing theexposure of the clusters to sunlight and aircirculation. Normally, removal of one to threeleaves per shoot is sufficient. Leaf removal trialsat the Orchard Mesa Research Center indicateminimal sunburning occurs if fewer leaves areremoved on the west side of the canopy. Afternoon sun can be extremely hot in westernColorado.

The ideal time for leaf removal is 3-4weeks before veraison (Veraison is the time

when berries begin to color). Lateral leaves maydevelop and require the practice to be repeatedlater in the season if leaf removal occurs too early. Avoid exposing shaded fruit in mid-late summeras sunburn can occur. Fruit clusters exposed tothe sun in the early season are less prone tosunburn. Mechanized leaf removal is currentlypracticed throughout Europe, South Africa,Australia, California and in some vineyards inColorado. The machines perform best withpositioned canopies such as vertical shootpositioned trellis.

Crop ThinningCrop thinning is a final adjustment

technique of crop regulation that results in themost significant fruit quality improvement. Cropthinning adjustments may be necessary to maturethe fruit earlier or change wine style. Vigorousvarieties such as Seyval blanc and Dechuanachave high initial fruit set and continue to produceabundant flowers late in the season which must beremoved for proper fruit composition andmaturation. The earlier the thinning, the greaterthe benefit to the remaining inflorescence. Early

inflorescence thinning, i.e., before flowering, is anoperation that is rapid and easily visible. Bunchthinning or cluster thinning is done after floweringand set. This operation involves removal ofundersized, poorly-set or immature clusters. Researchers in Italy (Ferrini et.al. 1995) haverecently shown the best time to cluster thin"Sangiovese" grapes was at the veraison stage. They found at that time, quality is not impaired,clusters are more visible, thinning is faster andmore accurate.

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Hedging, Trimming or ToppingHedging, Trimming or topping consists of

cutting off shoot tips during the early to midsummer. Late season trimming should be avoidedsince lateral regrowth may be stimulated andcause a delay in fruit maturation. Trimming toless than 10-12 nodes may impair fruit ripening. If trimming is not performed previous to a lateseason topping, healthy leaves could be removedfrom the canopy exterior exposing previouslyshaded older unproductive senescing leaves andthus lowering fruit ripening potential. Non-positioned canopies are very prone to thispractice.

If vine trimming is needed for increasedlight exposure, spray penetration, harvesting or toease the application of bird netting, etc.,alternative practices should be considered. Controlling vine vigor through proper irrigationmanagement, fertilization, use of an improvedtrellis system, or matching variety to site arebetter viticultural strategies than vine trimming. Vine trimming is a temporary "band- aid" solutionto vineyard canopy problems.

Nutrition Analyses and Foliar SpraysGrapevines have fewer mineral

deficiencies and a lower plant food demand thanmany other horticultural crops. Grapevines canadapt to a wide range of soil types and, if soildepth, texture, and water conditions are favorable,will survive and bear salable crops in soils withpoor fertility.

Sixteen elements are known to benecessary for normal plant growth: carbon,oxygen, hydrogen, nitrogen, phosphorus,potassium, calcium, magnesium, sulfur, zinc,boron, iron, manganese, copper, molybdenum,and chlorine. Plants take three of these, carbon,oxygen, and hydrogen, primarily from air andwater. The other 13 are absorbed from soil by theroots and divided into two groups, macronutrientsand micronutrients. The last seven elements listedabove are micronutrients and are used in smallerquantities than the macronutrients.

The function of each element in the plant'smetabolism is beyond the scope of thispublication; however, the vineyardist generallycan determine deficiencies and/ or excesses withthe proper laboratory diagnostic methods. Laboratory soil analysis is used to appraisevineyard problems related to Ph, salinity, andcertain toxicities. Soil analysis is not a reliablemeans of determining nutritional problems andfertilizer requirements. Field research hasrepeatedly shown inconsistent relationships

between soil nutrient levels and grapevine needs.Tissue analysis (TA) is a much more

effective and reliable means to determine vineyardnutrition than soil analysis. TA determines theconcentrations of nutrients the grapevine is able toremove from the soil. A typical complete TA willassess levels of nitrogen (N), phosphorus (P),potassium (K), calcium (Ca), magnesium (Mg),zinc (Zn), manganese (Mn), boron (B), iron (Fe),and sometimes sulfur (S) and sodium (Na), allexpressed either as percent or as parts per million(ppm). TA is another tool that helps thevineyardist establish a guideline for proper vinenutrient levels.

Sample timing is extremely important;samples must be taken during bloom time, thenearer to full bloom the better. The plant part tosample is the leaf petiole, and petioles from leavesopposite the blossom clusters toward the base ofthe shoot are preferred. Each sample shouldrepresent not more than five acres; areas ofdifferent soil types and vine strength should besampled separately. A representative sampleconsists of 75 to 100 petioles (one per vine) fromvines uniformly distributed over each area. Puteach sample in a new, clean brown kraft paperbag, label it with pertinent information -- e.g.,name, date, variety, location, and foliar spraysused or fill out an information sheet supplied bythe laboratory. Both soil and tissue samples canbe sent to the Soil Testing Laboratory, Colorado

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State University, Fort Collins, CO 80523. Information on current costs per sample can beobtained from your county Cooperative Extensionoffice.

Critical nutrient levels have not beenestablished for Colorado conditions, andinterpretations of the analysis can be comparedonly to other viticultural areas with similarconditions until further research has beenaccomplished.

NitrogenNitrogen is acknowledged to be one of the

most important and most likely limiting nutrientsin grapevines. Nitrogen is the essential elementused in greatest amounts by vines. Nitrogen isneeded for growth and development. Grapevinesuse nitrogen to build essential compoundsincluding proteins, enzymes, amino acids, nucleicacids, and pigments including chlorophyll andanthocynanins of fruit.

Once absorbed by the vine, nitrogen canbe lost through fruit harvest and annual pruning ofvegetation. Previous research has determined thaton average, each ton of fresh grapes containsabout 3.5 pounds of nitrogen. A harvest of 5tons/acre would remove approximately 18 poundsof nitrogen per acre. The depletion of nitrogenwould be even greater if cane prunings areremoved from the vineyard. (Canes contain about4.5 pounds of nitrogen per ton of grape.) Mostsoils will eventually be depleted of readilyavailable nitrogen if supplemental additions arenot made. Nitrogen depletion will occur mostrapidly with soils low in organic matter content(typical in western Colorado). Soil higher inorganic matter content can more easily convertorganic nitrogen to available forms (nitrate andammonium ions) capable of being absorbed by thevine.

Symptoms of nitrogen deficiency:The classical symptom is a light green

color of leaves, as opposed to dark green leaves ofvines receiving adequate nitrogen. If the leavesshow this uniform light green color, it will be

most noticeable on basal to mid-shoot leaves. Newly developing leaves often have a pale greencolor and should not be confused with nitrogendeficient leaves.

Some growers confuse nitrogen deficiencywith iron deficiency. In western Colorado soil pHis typically in the range of 7.3 to 8.4. High pHsoils like these make iron unavailable to the vinewhich is often confused with nitrogen deficiency. Symptoms of iron deficient vines are easy todetect. the classical symptom is a pronouncedintervenal leaf yellowing. The veins of amoderately iron deficient grape leaf remain green. In Colorado, Iron deficiency is typically visible bylate June. Nitrogen deficiency on the other handshows complete fading of green color includingthe veins. Other symptoms that point to nitrogendeficiency are a slow rate of shoot growth, shortinternodal length, and small leaves. Insufficientnitrogen can also reduce crop through a reductionin cluster, berries and berry set. Note that otherfactors such as drought, insect pests, disease andovercropping can also cause similar nitrogendeficiency symptoms.

Nitrogen and vine cold hardiness:The belief that any added nitrogen will

reduce cold hardiness of a vine is amisconception. The addition of moderateamounts of nitrogen (20-40 pounds of actualnitrogen per acre) will not reduce the vines coldhardiness level and will likely improve theiroverall performance.

Correcting nitrogen deficiency:Maintaining an appropriate nitrogen status

is based on past experience, vine performance andsupplemental use of bloom-time analysis fornitrogen concentration. Adequate nitrate-nitrogenlevels at bloom time range between 350 - 1200ppm for most grape varieties. Site, variety andyear to year differences may exist. This data isbased on leaf petioles taken from opposite clustersat full bloom. If nitrogen fertilization is needed,application of 20-40 pounds of actual nitrogen peracre on sandy loam soils is a good starting point

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for mature vineyards. Young vineyards (first andsecond growing season) in need of nitrogenfertilization typically require no more than 30pounds of actual nitrogen per acre. It occasionallytakes two years for added nitrogen to have animpact on vine performance. This is becausemuch of a vines early-season nitrogen needsdepend on nitrogen stored in the vine from theprevious

Time of Application:Nitrogen fertilizer should be applied

during periods of active uptake to minimize lossthrough soil leaching. This includes the periodform bud break to veraison, and if leaf fall has notoccurred, immediately after fruit harvest. Nitrogen is very mobile in the soil and applyingnitrogen while the vine is dormant and notactively absorbing nutrients should be avoided.

Multiple applications of nitrogen arepreferred over one mega spring application.

Applying Nitrogen:Apply nitrogen within 1 -2 feet of the vine

or where absorption can be aided by irrigation. Nitrogen should be immediately incorporated intothe soil by discing, irrigating or if plannedaccordingly, apply it before a rain. Incorporatingnitrogen into the soil minimizes volatilization andhence loss. Application can be achieved bybanding, injecting through the drip system or handtilling the soil around the vines. Banding with amodified tractor-mounted fertilizer spreaderworks well for large vineyards without dripinjection capability. Incorporating nitrogen byhand tilling a ring 15 - 20 inches from trunks ispractical for small vineyards.

Calculating Actual Nitrogen:There are several forms of nitrogen

fertilizer commercially available such as Urea(46%), ammonium sulfate (21%) or ammoniumnitrate (35%). Recommendations for actualnitrogen must be translated into rates based oncommercial formulations. for example, arecommendation for 45 pounds of actual nitrogen

per acre would require 98 pounds of ureafertilizer/acre (45#/46% = 98) or 128 pounds ofammonium nitrate fertilizer/acre (45#/35% = 128)or 214 pounds of ammonium sulfate fertilizer/acre(45#/21% = 214).

Foliar Sprays:A properly applied foliar spray program

usually focuses on micronutrients and can bebeneficial. Before applying any nutrient spray, alaboratory analysis of petiole samples fromaffected and normal leaves and a soil analysisshould be performed and evaluated. This allowsyou to base your decision with more evidencethan just visual symptoms. Foliar spray productsare not cheap and may be of little benefit ifimproperly applied. Micronutrients can beextremely toxic even in small amounts. They cankill vines if applied in excess. Some nutrient-deficiency symptoms can be confused with factorsother than nutrient supply. Care should be takenbefore applications are made to verify visiblesymptoms by tissue analyses.

Consider your foliar spray program as asupplement to basic root feeding. The micro-nutrients most commonly applied in foliar formare manganese, zinc and iron. Boron also can beconsidered, but deficient levels are not common inColorado soils. Macronutrients generally are noteffective or practical as foliar fertilizers andshould be soil-applied either by spreader, hand, ordrip system. Correcting a deficiency andcontrolling growth are major concerns inColorado, and trying to achieve this with acombination tank mix of N, P, K, Mn, Zn, Fe, andB may lead to increased vigor problems and,hence, increased winter damage. "Witches brew"tank mixes of pesticides and foliar nutrientsshould be avoided as phytotoxicity and berryscarring have been reported in California. Thefollowing is a brief summary of materials, rates,and trial studies for Mn, Zn, and Fe as foliarnutrients. The information was gathered from theWine Advisory Board Research Report (Oregon)and the UC-Davis publication #4087, GrapevineNutrition and Fertilization.

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Zinc deficiency may be corrected by applying a foliar spray two or three weeks beforebloom (10 to 15 cm shoot growth or near tightcluster stage); this helps improve berry set. Thevines should be sprayed with enough volume towet the flower clusters and the underside of theleaves. Treatments applied with a dilute sprayer(100 to 150 gal/acre) result in more Zn absorptionthan a concentrate sprayer application (20 to 30gal/acre) when comparable rates of Zn are used.

A number of products containing 50percent Zn are available under various tradenames. These products (basic zinc sulfates) willbe neutralized to prevent foliage burn. Zincsulfate (36 percent Zn) alone has no neutralizerand must be used with caution to prevent foliageburn. Studies in California have shown thatneutral zinc products containing 50 to 52 percentZn to be the most effective on a label rate per acrebasis. Chelated Zn (EDTA 14 percent Zn)materials are available, but are a little moreexpensive on a cost per acre basis than the basiczinc sulfates. The zinc sulfates are fully soluble inthe spray tank, whereas basic zinc sulfate is notand requires good agitation to remain insuspension. Soil application beneath dripirrigation emitters may be more effective since itprovides more concentrated placement with morecontinuous wetting for zinc movement into theroot zone. Deficiencies were nicely corrected in adrip irrigation trial where rates of liquid zincsulfate (12 percent Zn) at 4 to 9 fl. oz. per vineand liquid zinc chelate (EDTA 6.5 percent Zn) at0.25 to 1.8 fl. oz. per vine were tested. However,a foliar spray treatment in this moderatelydeficient trial vineyard was equal to the best dripsoil treatments (zinc sulfate) and would be themost cost-effective treatment.

Manganese deficiency rarely is a problem,but can occur in soils with high Ph values such asthose in many Colorado vineyard sites. A Mndeficiency has little practical effect on vine yieldssince it appears in late season on older leaves thatcontribute little to vine function. The symptomsbegin on the basal leaves as a chlorosis betweenthe veins. The only effect appears to be areduction in leaf chlorophyll. Manganese sulfateat 2 to 3 lbs per 100 gal of water applied as afoliar spray at the loose cluster stage has correctedthe deficiency in some California vineyards. Higher rates should be avoided as it may causeminor leaf burn. Manganese chelate productshave been used as foliar sprays with somesuccess.

Iron deficiency is considered one of themost difficult nutritional problems to correct. Foliar spray treatments of Fe chelates atmanufacturer recommended rates or of ferroussulfate at 4 to 6 lbs per 100 gal of water result in atemporary correction, at best. Because Fe isnonmobile in plants, a spray benefits only existingfoliage. If chlorosis is severe and persists,repeated applications at 10 to 20-day intervalsmay be necessary. Experience in Colorado hasfound that soil treatments with Fe chelates workbest and tend to last longer; however, they areexpensive.

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Estimating Grape YieldsCrop estimation, also called crop

prediction, is the process of projecting asaccurately as possible the quantity of crop thatwill be harvested. Why estimate the crop? Obviously, growers need to know how much cropthey produce. Also, growers would like to knowwhether their vines are overcropped orundercropped in order to conduct the necessaryadjustment. This is especially important in coldareas such as Colorado where winter freeze andspring and fall frosts could change the cropquantity each year.

The formula described below is the mostpopular and easy to understand system to estimateyield. This system is used successfully in otherwinegrape growing regions of the country. Thissystem provides only an “estimate” of yield whichshould never be considered “final”. Componentsof yield vary each year depending on the year,site, variety, and cultural practices. The followingformula can be used to estimate crop withreasonable accuracy:

PY = (NV x NC x CW)/2000

Where PY = predicted or estimated yield(in tons per acre)NV = actual number of vines/acreNC = number of clusters per vineCW = cluster weight (in pounds).

According to the formula, the growerneeds to measure the following 3 parameters eachyear: the actual number of vines per acre, thenumber of clusters per vine, and the clusterweight. These parameters are discussed belowwith examples.

1) Actual number of bearing vines peracre: the maximum number of vines per acre isdetermined by the row and vine spacing. Forexample, a vineyard spacing of 5 x 10 feet willhave 871 vines per acre. Almost always the“actual number” is lower than the “maximumnumber” of vines per acre due to vines missing

for several reasons such as diseased vines, winter-injured vines, etc. For these reasons, each yeargrowers need to physically count the missingvines, subtract that number from the maximumnumber to get an accurate count of the bearingvines. If 10% of the 871 vines/acre (i.e. about 87vines) were missing or nonbearing then the actualnumber of bearing vines/acre is 871-87 = 784.

2) Number of clusters per vine: thisnumber will depend on how many nodes (buds)are left after pruning. The number of clusters pervine can be counted as soon as they are visible(i.e. two weeks before bloom) or as late as berryset (i.e. BB size stage). The advantage of doingan early count is that clusters are readily visibleand are not obscured by leaves. The number ofvines on which to count clusters depends onvineyard size and uniformity. For example, in 1to 3 acre-vineyards with vines of a uniform age,size, and pruned to the same bud number, only 45of the vines need to be counted. For practicality,10 to 20 vines could be used; however, bear inmind that the higher the number of vines selectedfor cluster count the more accurate the yieldestimate will be. In larger, non-uniformvineyards, more vines should be selected. All theclusters on the sample vines should be counted. Also, the vines should be selected methodically,e.g. select every 10th vine in every other row.

3) Cluster weight: this is the componentof yield that varies the most from year to year. Itis influenced by environmental conditions. Forexample, wet weather during bloom could causepoor set and may lead to low cluster weight; alsoa dry summer tends to reduce berry size and thusmay decrease average cluster weight. Otherfactors that may affect cluster weight includecultural practices (irrigation, fertilizers), diseases,insects, and birds. Cluster weights at harvest are akey part of any yield prediction program. Thegoal of obtaining cluster weight at harvest is notto predict the yield that year, but to providerecords for yield prediction in subsequent years. Clusters can be collected from picking bins afterharvest. This is an easy way to sample clustersfrom the bin but not as accurate as sampling

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clusters from the vines. The same vines used forcluster counts could be used for cluster weights. Clusters from each sample vine are picked andthen weighed. The average cluster weight isobtained by dividing the total cluster weight pervine by the number of clusters per vine. Growerswho do not have these data (but hopefully will inthe future!) could use estimates of cluster weightsshown in Table 5 on the next page (source: CSU-OMRC and Washington State University).

4) Example of predicted yield ofChardonnay for 1997 harvest at OMRC: -spacing = 5 x 10 feet or 871 vines/acre-missing/nonbearing vines = 1% or about 9 vines/acre-actual number of bearing vines = 871 - 9 = 862 vines/acre-average cluster count = 45 clusters/vine-average cluster weight (based on 1996 harvest) =0.3 lbs.-predicted yield = (862 x 45 x 0.3)/2000 = 5.8tons/acre

Even with thorough sampling, accurate vinecounts, and many years of average cluster weightdata the actual crop tonnage at harvest can vary. However, accuracy with this system is very goodand usually falls between 75 - 100%.

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Table 5. Average cluster weights for wine grape varieties in Washington and Colorado.

Variety Cluster Wt. (lbs.) in WA Cluster Wt. (lbs.) At OMRC*

Whites:Chardonnay

White RieslingGewurztraminer

SemillonMuscat blanc

ViognierSauvignon blanc

Pinot blancChardonel

Seyval BlancVignoles

0.3 - 0.450.25 - 0.30.25 - 0.30.4 - 0.50.4 - 0.5

–0.25 - 0.3

––––

0.30.340.20.460.570.27

–0.30.230.240.18

Reds:Merlot

Cabernet SauvignonCabernet franc

Pinto noirShiraz

SangioveseDolcettoMalbecNorton

Lemberger

0.3 - 0.450.3 - 0.40.4 - 0.45

––––––

0.4 - 0.5

0.360.370.290.340.280.610.40.360.12

–

*Cluster weights taken at OMRC are based on 1996 harvest data.

Harvest TimingThe greatest potential of any wine grape

variety is realized only when it is harvested at theproper time. The maturity of grapes is usuallybased on three parameters: sugar content, acidcontent and Ph. All of these change over time,and the rate at which they change is based largelyon the temperature regime in which the grapesexist. Each parameter and its means ofmeasurement is discussed below.

Sugar Content: Grape sugar contentremains low until a midseason point, usually inJuly or August in Colorado, at which time it

begins to increase rapidly. This stage is calledveraison. From that point on, if nothing else islimiting, the sugar content will increase over timeand do so more rapidly at higher temperatures. The best way to measure sugar is with a hand-heldrefractometer which uses the degree to which lightis bent by the dissolved sugar in the juice to give aquick visual measure of the "dissolved solublesolids." The scale on these instruments is given inoBrix or oBalling which for practical purposes canbe considered to be percent sugar by weight. These really are worth their approximate $150 to$250 cost since they can measure the sugar

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content of the juice of single berries.A hydrometer is a less expensive device

which, when floated in a cylinder of juice, sinksto a level dependent on the juice density whichalso corresponds to sugar content. Around 50 to100 ml (2-3 fl. oz.) of juice are required to do thistest.

The alcohol content of a dry, finished wineis approximately 0.55 times the sugar content atharvest. White wine grapes are usually harvestedbetween 18 and 24 percent sugar depending onthe intended style of the wine. Red wine grapesare generally harvested at 21 to 25oBrix.

Acidity: The organic acid content ingrapes (mostly malic and tartaric acids) increasesthrough the early season until a point nearveraison. From that point on, acid is lost throughthe grape skins by evaporation, and that processoccurs more rapidly at high temperatures. Acidityis more difficult to measure, but choosing the besttime to harvest depends upon having a goodestimate of acidity. A sample of juice of knownvolume (usually 10 milliliters) is diluted withdistilled water to make 40 milliliters. Thismixture is then stirred while adding a base(sodium hydroxide or NaOH) of known strength(usually 0.1 Normal). In the example describedhere, the number of milliliters of base required toraise the pH of the juice to 8.2 is divided by 10. This results in a number called the percent acid(grams/ 100 ml). The standard strength base canbe purchased and the pH 8.2 end point can bedetermined by a color change of an indicatorsolution. If measured in that manner, it is notnecessary to have a pH meter available. Thedesired acid content of a wine varies greatly withthe intended style of the wine; high acids (above.9 percent) can be useful in sweet finished winesand for those who have a taste for high acid drywines. Acids that are too low are of greaterconcern (i.e., below .7 percent for white and .6percent for red).

pH: The pH of a wine is only indirectlyrelated to acidity; pH tends to increase afterveraison. But, if pH becomes too high, the winewill not be stable. The optimum pH range is 3.0

to 3.4, but it is difficult to measure pH accuratelyenough using specially treated papers. A pHmeter, an electronic device, is a rather expensivepiece of equipment, but it is standard in anycommercial winery lab. Most home winemakersfunction without a pH meter.

Sampling: Sampling is critical indetermining crop maturity. You can determinethe sugar content of a single berry with arefractometer, but there is a wide variation inmaturity between berries even on the same cluster. To make an accurate estimate of the sugar, acidand pH of a crop, draw a representative sampletaken from as many parts of the block, as manyvines, and as many clusters in different sunexposures as possible. Younger vines and vinesthat are somewhat more water stressed will havehigher sugar and lower acid. Clusters exposed tothe sun will be higher in sugar and lower in acidthan those on the inside of the canopy. Oftenthere are two size classes of berries (especially oncultivars such as Chenin blanc) that differ greatlyin maturity. In order to get a good estimate forpicking, it is recommended that at least 200berries be plucked with an effort to spread thesample across all the variations which might exist. It is easier to sample exposed clusters and exposedberries, so one tends to overestimate sugar contentand underestimate acidity. It is also importantthat the grapes be squeezed to approximately thesame degree to which they will be when actuallypressed since higher sugar juice is released withonly mild crushing. Unless it is very hot, weeklysampling is sufficient to follow trends in maturity. A few samples carefully collected on a weeklybasis are better than many inaccurate onescollected on a daily basis.

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Pest Management/Control

All too often in the past, only limitedattention has been given to options for pestmanagement. With the increasing concern forchemical toxicities and consumer risk and thedecreasing number of chemical control options,the wise grower will consider all of the availableoptions and their cost (risk) : benefit relation-ships. Sometimes an option may provide a lowerlevel of pest control that may in fact still besatisfactory; conversely, an option that

provides the greatest control probably will be thepoorer choice if satisfactory control at lower environmental or monetary cost is availablethrough other options. Remember, the goalshould always be satisfactory control at the leastcombined environmental, health, and monetarycost. Color identification sheets for somediseases and insects are appended to this guide.

Disease ManagementClimatic conditions have a large role in

disease development and occurrence. The warmerand wetter the climate, the more numerous andsevere disease problems are likely to be for thegrape grower. Colorado generally has an arid tosemiarid climate, with 7 to 20 inches annualprecipitation in areas where grapes might begrown. Thus, even in the wetter areas (i.e., 15 to20 inches precipitation per year), diseaseproblems should be manageable with advanceplanning and attention throughout the growingseason.

Of the eight grape diseases reported orsuspected in Colorado, two (grape powderymildew and crown gall) are very commonthroughout the state. Three others (Botrytis bunchrot, sour bunch rot, and Verticillium wilt) occurwith varied frequency and distribution. Oc-currence of one virus disease, grape leafroll, hasbeen confirmed in several western Coloradovineyards planted with non-certified nurserystock. Suspected observations of two otherdiseases (Eutypa dieback and nematode-vectoredfanleaf degeneration) have been reported but notyet confirmed. Occurrence of downy mildew,Phomopsis leaf spot, and black rot is highlyunlikely in western Colorado and not too likelyeven in eastern Colorado, although some of theFront Range areas might have sufficient summerhumidity and rainfall to allow them to occur.

Powdery Mildew: Grape powderymildew (caused by the fungus Uncinula necator)is an important disease in almost all grapegrowing regions of the world, but it is the mostimportant in relatively dry climates. UnderColorado conditions, powdery mildew is the mostcommon and most destructive single grapedisease. Uncinula necator originated in NorthAmerica and thus the native grapes are generallyless severely damaged by mildew infection. Grapes which originated elsewhere in the world,particularly the V. vinifera cultivars, are oftenhighly susceptible and easily damaged bypowdery mildew since they were selected forcenturies in the absence of that pathogen. Hybridcultivars vary in their mildew susceptibility.

Powdery mildew fungi infect a widevariety of crops, but each species can be quitespecific. The mildew that infects grapes does notinfect any other Colorado crop and the powderymildews of other crops (e.g. apples, cucurbits,roses...) do not infect grapes. Powdery mildewsare unique among fungal pathogens in that they donot require free moisture for spore germination orfor penetration of the host plant. The spores arespread by wind. After arriving on the plantsurface they germinate and grow a short distancebefore forming a structure called an appressorium. From that structure a small peg is formed thatpenetrates the cuticle and epidermal cell wall. A

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specialized feeding structure called a haustoriumdevelops inside the penetrated cell, but that is theextent of fungal development inside the plant. After an infection is established the continuinggrowth of the fungal colony is on the surface ofthe plant. Hyphae radiate from the firstpenetration site and periodically penetrate morecells to establish more haustoria for nutrientuptake. As the colony develops, columns ofbarrel shaped spores are produced. Whencolonies grow large enough to be visible or whenmultiple colonies are present, the infected plantsurface develops a white to gray, felt-like topowdery appearance. The entire process frominfection to sporulation can take anywhere from 5to 21 days, depending on temperature. Powderymildew grows most rapidly at moderatetemperatures (�70F) and is very slow at extremelyhigh temperatures (>90F). Mildew responds toleaf temperature, not air temperature andtranspiring leaves are usually much cooler thanthe surrounding air.

Almost any green tissue of a grapevine issusceptible to mild infection including tenderparts of the shoot, blossoms, leaves, berries, therachis and pedicles. Immature tissues are alwaysmore susceptible. Severe shoot and leaf infectioncan reduce yield, reduce overwintering hardinessor stunt growth, but the most common form ofmildew damage concerns the fruit. When berriesare infected, the epidermis under the colonydevelops a network of russeted scars. This can beunsightly (a problem for table grapes). Moreimportantly, if the berry is still expanding thedamaged portion of the skin fails to grow and theberry cracks. This enhances secondary infectionby fungi and acid bacteria. Even withoutcracking, severe fruit infection reduces yield, andthe presence of mildew spores and mycelium canimpart off-tastes to the wine. Berries aresusceptible to infection from before bloom untilveraison. When berries have around 11% sugar,they can be considered safe from further infectionand the mildew present on the berries will soondie. Even so, the rachis remains susceptible.

Like all powdery mildews, Uncinula is an

obligate parasite -- it can only live and grow onthe host grape tissue. It overwinters in two ways. Mycelium can enter the developing buds andremain alive inside of the bud scales to growagain the following spring. When the necessarymating types are present, the fungus can alsosurvive in its resistant, sexual spore bearingstructures called Cleistothecia. These small (thesize of a pinhead) structures can sometimes befound on leaves and fruit late in the season. Theyhave appendages with hooked ends which cancatch on the bark of the cordon or trunk. Cleistothecia which remain on the vine canmature and produce ascospores there in the spring,and these can be forcibly ejected following rainsto infect the emerging grape shoots. It is not clearhow much overwintering inoculum in Coloradocomes from cleistothecia and how much frominfected buds.

Whether originating from infected buds orfrom Cleistothecia, even a small population ofpowdery mildew can build up through the seasonbecause of the relatively short infection cycledescribed earlier. To the grower, powdery mildewinfection often appears to have occurred suddenly,but actually it was building logarithmically longbefore it was found. It is for this reason thatpowdery mildew control methods must bepracticed pro-actively -- long before infectionscan be found in the vineyard.

The key to a successful powdery mildewcontrol program is the assumption that mildew isalways present in the vineyard and must either beprevented from spreading or repeatedly killed-back so the epidemic does not develop to levelsthat will damage the crop. Begin spraying as soonas practical after buds emerge in the spring and continue steadily until veraison. Overall mildew"pressure" varies from year-to-year based onoverwintering conditions and on the temperaturepattern of the given season, but any grower whoneglects to maintain a good mildew program willeventually suffer severe damage.

There are currently three registered classesof fungicides for powdery mildew control ongrapes. Each has its own advantages and

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weaknesses so that the optimal control programoften uses 2 or 3 classes at one point or anotherduring the season. Each class is described below:Sulfur: Elemental sulfur is the oldest knownfungicide and was the mainstay of mildew controluntil recent times. It is recognized as suitable for"organic" production. Sulfur particles on the plantslowly sublimate (change from solid directly togas) and generate sulfur compounds which cankill germinating spores of powdery mildew. Sulfur is a completely preventive fungicide and isonly effective immediately in the vicinity of theparticle. Excellent coverage is necessary forcontrol with sulfur. Sulfur is available either as adust (use rates 5-15 lbs/acre) or as a wettablepowder for water application (use rates 2-6lbs/acre). Dusts have the advantage of potentialhigh speed application and penetration of densecanopies but they have the disadvantages ofsubstantial drift which can damage neighboringcrops and irritate neighbors. Sulfur dust should beapplied on a 7-10 day cycle. Wettable sulfur canbe used on a slightly longer spray interval (7-14days) and does not have problems with drift. Ittakes longer to apply and can be more difficult todeliver to all parts of the canopy. With either kindof sulfur, high temperatures (>90F) can speedsublimation to the point that leaves are damaged. Very low temperatures (<55F) do not allowenough sublimation to be effective. Sulfur ishighly susceptible to rain wash-off and must bere-applied after any significant rain. When usingsulfur for mildew control, the basic goal is to keepa coating of relatively fresh sulfur on the entirevine as consistently as possible. The faster thevine is producing new, unprotected tissue, themore frequent the sulfur applications must be toreestablish the protective barrier. Sulfur does notkill established mildew infections, it simply slowsthe progress of the epidemic.

Sterol Inhibitors: There is a class ofsynthetic, systemic fungicides variously referredto as SIs (Sterol inhibitors), EBIs (Ergosterolbiosynthesis inhibitors), or DMIs (Demethylaseinhibitors). All these names are more or lessspecific descriptions of the kind of fungal

enzymes which are inhibited by the fungicides. All of those available for use on grapes inhibit thesame enzyme in the ergosterol biosynthesispathway which is important because strains whichbecome tolerant to one DMI fungicide are alsomore tolerant to other DMI products (crossresistance). These fungicides are all applied inwater and move to a certain extent from cell-to-cell in the plant and with the transpiration stream. The systemic movement is not sufficient to movefungicide to new tissues, but it does helpovercome small inconsistencies in spray coverage. DMI fungicides can be very potent tools forpowdery mildew control and are particularlyvaluable during bloom and immediately afterwhen berry tissue is expanding so rapidly thatsulfur protection is difficult to maintain. DMIfungicides can kill a young mildew colony (1-3days), but are not able to kill established,sporulating infections. Although they have thiscurative action, they should be approached asprotective fungicides and used on a 14-18 dayspray schedule. Tolerance to DMI fungicides iswell documented, but is not a dramatic all-or-nothing type of resistance. Even so, it is best tolimit the total number of DMI sprays used in aspray program, to use other fungicides as part ofthe program, and to avoid using DMI fungicideslater in the season when the selection pressure isapplied to a large mildew population. As newclasses of systemic fungi-cides are introduced, thesame general guidelines should apply. Do not relyon a single mode-of-action throughout the seasonand use potent systemic treatments early to mid-season before larger mildew populations arepresent.

Impact Fungicides: A class of powderymildew control tools has been introduced recentlythat is described as "impact fungicides". These arematerials that are capable of killing mildew sporesand mycelium during direct contact of the spraysolution or suspension. These materials arealmost strictly curative in their activity becausethey have no effect on new spores that arrive after

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Standard Fungicide Programs

The most highly recommended fungicide programs for grapepowdery mildew control are as follows:

Standard DMI program:1. Wettable or dusting sulfur starting at budbreak and

continuing on a 10-14 day pattern (7 days for dust) untilbloom or 10" shoot growth.

2. DMI applications every 18 days from bloom or 10"shoot growth until the total, annual dosage/acre has beenapplied (usually around 3 sprays).

3. Sulfur applications on a 10-14 day interval (7 dayinterval for dust) until veraison.

Standard Sulfur Program:1. Wettable sulfur starting at budbreak.2. Dusting or wettable sulfur on a 7-14 day cycle until

veraison.

Older recommendations (first written in 1905) began theprogram at 6 or 12 inches of shoot growth, but recent research indicatesthat much better control is usually achieved by starting the sprayprogram earlier.

These programs are commonly modified by grape growersfor various reasons.

DMI program modified for resistance management:� Alternation: sulfur sprays inserted between the DMI

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the spray dries. Any type of impact fungicide isbased on emulsions of either plant oils orparaffinic mineral oils. The mineral oils are notvery compatible with a spray program that alsoincludes sulfur. Under some conditions, a sulfurtreatment as much as two weeks before or after anoil application can lead to severe burning ofleaves. The other type of impact fungicides arepotassium salts of naturally occurring fatty acids. These materials are compatible with the use ofsulfur and can be particularly useful for "rescue"applications when mildew infection is "flaring up"in isolated areas or because of failure of theprevious preventive control program. A sprayprogram (10-14 day interval) using only curativefatty acid products has been shown to give season-long mildew control. Fatty acids are alsoattractive alternatives when conditions are too hotfor sulfur or if the winemaker is concerned aboutsulfur residues carrying over to the must atharvest. Oils (and to a lesser extent fatty acids)effect the appearance of the waxy surface of theberries. This does not effect their resistance toother diseases or resistance to water, but it isgenerally considered unsuitable for table grapeproduction.

Crown Gall: Crown gall, a bacterialdisease caused by Agrobacterium tumefaciens,can be a significant problem in some Coloradogrape plantings. Galled vines frequently havepoor shoot growth and fruit production, andportions of the vines above the galls often dieprematurely. Vinifera grapes appear to be mostsusceptible to crown gall attack and damage, butsome V. labrusca cultivars (e.g., Niagra,Dutchess, and Isabella) also can become heavilyinfected. Hybrids that are often infected includeAurore, Chancellor, and Cayuga White. InColorado, Merlot appears to be more susceptibleto crown gall than Riesling.

The bacterium lives in soil but, whenpresent at a plant wound, it invades the host celland transforms it into an undifferentiated gall typeof growth. The galls interfere with normal sugarand water transport in the host and, depending onthe location and size of the gall, can kill the plant

or stress it so that it becomes non-winter hardy. Injuries for gall initiation are most common in thenursery and during planting, but winter freeze-cracking of trunks provides another potential entrypoint in Colorado.

Crown gall has been controlled on somehosts by use of another bacterium that produces anantibiotic that inhibits some strains of thepathogen. Unfortunately, the common grapestrain (biovar 3) is not sensitive to this antibiotic. Thus the biological control option (strain K84 ofA. radiobacter) is not effective in controllinggrape crown gall. An eradicant chemical such askerosene or Gallex can be used on the gall itself tokill gall tissues, but treated vines should bechecked for gall recurrence over the next year ortwo since new galls can develop at treated sites.

Use of management practices that reducewinter injury can be helpful because thedevelopment of crown gall is frequentlyassociated with the occurrence of freeze injury. Freeze cracking injury in the field allows theformation of galls on mature vines; thisoccasionally kills the trunk outright, and the vinemust be retrained from root suckers. Thus, insites prone to severely cold winter temperatures,growers should consider burying young vines inthe fall to reduce freeze injury and possible"hilling" of trunks in the fall to protect the crowntissues (and to protect replacement buds fromfreezing just in case they are needed for trunkrenewal the next season). Any galled woodshould be removed from the vineyard and burned. Recent research also has shown that thepathogen can become systemic within grape tissueand can be introduced into previously non-infested soil by planting infected grape plants. This points out the need to plant only pathogen-free vines, especially in new planting ground. Such a practice should help minimize crown galloccurrence in replanted ground and avoid the highincidence of disease that has often beenexperienced in new plantings.

Botrytis Bunch Rot: Botrytis bunch rot orgrey mold generally is present in all vineyards,but only occasionally causes problems in Colo-

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rado vineyards. Varieties with tight clusters(Chenin blanc, Muscat blanc, Gewurztraminer,Pinot noir, Rougeon, Sauvignon blanc, andRiesling) are usually the only ones damaged inColorado and usually only in seasons with cool,unusually wet summer weather. Both yield andquality can be reduced. Table grapes can losesubstantial fruit quality in the field, in storage, orin transit, but wine grapes suffer even moreserious damage to quality because of the chemicalchanges within the grapes brought about byinfection. Wines made from diseased fruit tend tobe less clear, have off-flavors and do not age well.

Affected bunches also can be affected bythe vinegar bacterium, Acetobacter sp., and acommon saprophytic fungus, Aspergillus niger inwhat is known as sour bunch rot (see next entry).

Control can be obtained through two non-chemical management options. Leaf removalaround the developing fruit clusters will increaseair circulation and decrease humidity levels withinthe canopy. This will reduce the liklihood ofbunch rot getting started. Secondly, varieties withvery tight clusters may be cluster thinned byremoving selected berries when young; this opensup the clusters to allow more air movementthrough them and thus reduce the potential forbunch rot.

Sour Bunch Rot: Sour bunch rot maycause damage to varieties with tight clusters(Chenin blanc, Muscat blanc, Gewurztraminer,Pinot noir, Rougeon, Sauvignon blanc, Riesling)in seasons where hot August weather isaccompanied by rains. Broken berries attract thevinegar fly that carries the vinegar bacterium,Acetobacter sp. The berries rot and develop anobjectionable vinegar order. The fungusAspergillus niger is often involved in thecomplex. This disease has no real control exceptby avoiding berry breakage by birds or otherfactors. To date, it has not occurred in sufficientabundance in Colorado to adversely effect winequality.

Verticillium Wilt: Verticillium wilt iscaused by the fungus Verticillium dahliae. Itoccurs only sporadically in Colorado, primarily in

vineyards planted in soils in which susceptiblecrops (e.g., sweet cherry, apricot, tomato,strawberry) have been grown.

Symptoms of Verticillium wilt mimicthose of drought stress. Shoot wilt, collapse, anddeath can be extremely rapid by mid-summer, andleaves and young berries just dry up and remainattached to the dead cane. The diagnosticsymptom, however, is the greyish to brownishdiscoloration of the vascular elements within thebase of the collapsing cane. This discoloration,best seen by cutting the bottom portion of the caneon a diagonal (an oblique cut), appears as greyishto brownish streaks associated with or within thevascular bundles.

The reason for the drought stress typesymptoms and the vascular tissue discoloration isthat the Verticillium fungus colonizes and plugsup the vascular tissues. Thus, as the need forwater transport increases with increasing summertemperatures, the infected vine simply cannotsupply enough water to the heavily colonizedcanes fast enough to keep up with demand. As aresult, the affected canes simply wilt and die.

This disease is mostly a problem in youngplantings between their second and sixth leaf. Bythe sixth leaf, vines that exhibited symptomsearlier but did not die recover and are not affectedthereafter. At that point, the disease generally isno longer a problem within the vineyard. Although early fruit production can be reducedand full production delayed by the disease, noeffect on yield has been shown in vineyards thatno longer show symptoms of Verticillium wilt. Thus specific control measures for the disease donot appear warranted other than avoiding any siteswhere the disease has actually killed grapevines.

Eutypa Dieback: Eutypa dieback is alsoknown as "dying arm" (formerly "dead arm"). Itis one of the most destructive diseases of woodytissues of commercially grown grapes. The causalfungus, Eutypa lata (synonym = E. armeniaca),and the disorder are most common in areas ofhigher rainfall and severe winters, but can beexpected in areas where the annual precipitation isabove 10 inches per year. Occurrence in areas

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with less than 10 inches precipitation per year isunlikely, but since many of the grape plantingswithin Colorado are likely to be within areaswhere apricots are grown, the possibility of thedisease does exist.

Characteristic symptoms of Eutypadieback begin with early season growth, whenshoot growth is 10 to 20 inches in length. Affected shoots are deformed and discolored, withmuch dwarfed internodes, and the leaves smallerthan normal, cupped and chlorotic. The leavesoften develop small necrotic spots and tatteredmargins with age. The diagnostic feature ofEutypa infection on arms with such symptoms is awedge-shaped zone of dark-brownish deadsapwood extending into the wood when the woodis cut in cross-section.

Control is available through a drenchingspray of benomyl applied at pruning to any largewounds or cuts on woody tissues (i.e., not theannually produced canes, but rather any tissue thatis two years old or older). This material iseffective in preventing spores from germinatingand gaining a foothold for infection; thus, it mustbe in place before the spores arrive. Applicationsmust be sufficiently drenching to be absorbed andtaken up into the vascular tissue to be effective,and they must be applied as soon as possible afterthe wound or cut is made. Manual treatment ofsuch wounds at the time of pruning will have thehighest probability of success. In Colorado'smore arid climate, those chances should berelatively high.

Virus Diseases: The two virus diseasesknown or suspected to occur within Colorado aregrape leafroll and fanleaf degeneration. In bothcases (the same is true for most other virusdiseases) problems can be avoided by plantingonly certified clean stock such as that grown inthe Pacific Northwest and in certified programs inCalifornia. The various viruses, in addition to thesymptoms for which they are generally known,appear to reduce the winter hardiness of the vines. In addition, some grape viruses are spread bydagger nematodes that occur within our fruitproducing soils. Thus importation of non-

certified nursery stock could import a potentialvirus problem that could spread within vineyardsand last in the soil even after the diseased vinesare removed. NON-CERTIFIED VINES orvines from questionable sources SHOULD NOTBE PLANTED OR USED FORPROPAGATION .

Grape Leafroll Disease : Grape leafroll,which results from infection with the grapeleafroll virus, causes chronic damage to affectedvines. Leafroll infection does not kill affectedvines, but yield loss of 20 percent has beenreported to occur each year for as long as thediseased vines were maintained within thevineyard. The disease is widely distributedbecause of past propagation from diseased mothervines, but was not known to occur withinColorado vineyards before the 1989 season. However, one confirmed occurrence in an entireplanting of Lemberger and a second in a secondleaf Cabernet franc planting in Mesa Countyillustrates the need to order only certified virus-free grapevines.

The disease is characterized by theoccurrence of colored leaves (yellow for lightfruited varieties or red to red-purple for darkfruited varieties) with green veins and downwardrolled leaves. These symptoms develop in latesummer beginning with the leaves at the base ofthe cane and proceeding toward the tip. However,since similar symptoms also can be produced (tosome extent) by cane or vine injury (from caneborers, crown gall, mechanical damage, crown rot,etc.), careful examination must be made to ruleout these other possible causes. General size ofinfected vines and plant structures (leaves, shoots,canes, trunk, and root system) is slightly smalleroverall than that of healthy vines. In addition, thedisease delays fruit ripening and reduces fruitcluster size and fruit sugar content; fruit color,especially in the red or black cultivars, is pale.

Control of the disease is relatively simple -- removal of the affected vines. No vector for thecausal virus is known, and natural spread incommercial vineyards is slow. This stronglysuggests that the primary source of infection is the

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diseased budwood from which vines werepropagated. Leafroll is an avoidable disease ifcare is taken to plant only virus-free vines.

Fanleaf Degeneration: Fanleafdegeneration, the oldest known virus disease ofvinifera grapes, varies with cultivar tolerance tothe virus. Sensitive cultivars are severely affectedwith infection causing decreased yields (up to 80percent losses) and fruit quality, progressive vinedecline and shortened productive vineyard life,reduced graft take and rooting ability of cuttings,and lower tolerance of adverse weather conditions(e.g., winter hardiness, heat and drought tolerance,etc.).

Diagnosis is complicated by the fact thatthe virus can cause any of three distinct symptomsyndromes. These focus primarily on leaf shapeand color patterns, shoot growth patterns, and fruitproduction effects.

The first symptom syndrome, infectiousmalformations, includes the most severesymptoms and is the best known of the symptomsyndromes. Its most obvious effects aremalformations of the leaves and shoots thatappear in the spring and continue throughout theseason, with a slight lessening in severity of theleaf symptoms severity during the summer. Leaves are variously deformed, oftenasymmetrical and puckered, with the leaf basetending to be more flattened (less of an angularnotch at the leaf base) and the veins less separatedto give the leaves a more open, fan-likeappearance (from which the disease derives itsname). The leaves also may have a chloroticmottle. Shoots are commonly malformed withshortened internodes, a zigzag or snake-likegrowth pattern, double nodes, abnormalbranching, and fasciations. Fruit set in vines withsuch symptoms is poor, and the fruit bunches arefewer and smaller than normal with shot berriesand irregular ripening.

The second symptom syndrome, yellowmosaic, exhibits little or no malformation ofshoots or leaves, but it does result in small fruitclusters with some shot berries. Its maincharacteristic is the bright chrome yellow

discoloration of early spring vegetative structures(leaves, shoots, tendrils, and inflorescences). Thediscolorations range from scattered yellow spotsto rings or lines to extended leaf mottling to totalyellowing. Affected vines are easily spottedwithin the vineyard in early spring, but are lessobvious by summer in areas with hot summerweather whey they begin to produce normal,green foliage.

The third symptom syndrome,veinbanding, consists of mid- to late-summerdiscoloration in mature leaves and severelyreduced fruit yield (to virtually zero). No shoot orleaf malformations are produced, but chromeyellow flecks develop along the main veins ofsome (but not all) mature leaves. The fleckingthen spreads somewhat into the interveinal areasof the affected leaves. Fruit set is poor and theclusters are straggly.

Grape fanleaf virus (GFLV) is spreadprimarily by a dagger nematode, Xiphinema index. The virus has no known natural weed hosts -- onlygrapes. However, the nematode can acquire thevirus in a single, brief feeding on an infected vineand can remain inoculative for up to eight months,even in the absence of host plants. Added to thisis the ability of grape roots to remain viable (and,thus, as sources of inoculum) for many years afterthe mother vine is removed. This makes controlextremely difficult once the nematode andinfected grape roots are present within a planting.

The best control for fanleaf degeneration isto plant only certified virus-free stock. Once thenematode and infected grape roots are present, theecological cycle of the nematode / virus / grapecomplex must be broken. This usually requires aprolonged fallow period with rigorous weedcontrol or eradication of the vector nematodeswith soil fumigants or both. Soil fumigation (athigh rates) works better in shallow than in deepsoils, as some nematodes can survive below thedepth the fumigant penetrates. Rootstocksresistant to either the virus or the vector nematodeor both are being developed and should beconsidered for use in renovated vineyard plantingswith a history of fanleaf degeneration.

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Insect & Mite Pest ManagementInsect and mite pest problems have not

been severe enough in Colorado to require aregularly scheduled spray program. However,with the continued increase in acreage planted tograpes, this could change. Grape pests known tooccur within Colorado vineyards or orchardsinclude: grape leafhopper, grape berry moth,grape cane borer, grape mealybug, grapeskeletonizer, sphinx moth, thrips, cutworms,cottony maple scale, thrips, and mites. Phylloxerais not known to occur currently in Colorado. With proper care in selection of plant sources andcareful examination of all materials beforeplanting, it is hoped that this pest can be kept outof Colorado. Leafminers are an occasionalproblem in backyard grape plantings but have notbeen a problem in commercial plantings to date.

Climbing Cutworms: Several species ofclimbing cutworms may be found chewing ongrapes in Colorado. These pests hide in the soilor debris beneath the grape trellis by day andmove up the vine at night to feed on buds just asthey are swelling and pushing in the spring. Theirfeeding leaves small (1/16 to 1/8 inch) tunnelsinto a bud; this kills the bud and results in croploss. Sprinkling a suitable carbaryl (Sevin) baitaround the trunk of each vine usually will stopthis damage. If the worms are living on the trunkitself, a spray may be necessary.

Grape Berry Moth: Grape berry mothscan be important pests of grapes in Colorado andcan cause serious fruit losses in some areas. Thelarval stage of this insect enters young berries andcauses them to wither as they mature. The insecttypically is found in American grapes such asConcord and in hybrids, but also can be found invinifera grapes.

There are two generations of the motheach year, with peak flights in mid-June and late-July. Adult moths emerge in late May fromoverwintering pupae and lay eggs singly on smalldeveloping grapes or cluster stems. If the berriesare too small, the larvae will make webs on thecluster stems and feed there until the berries are of

sufficient size to enter. Entry of the larvae intothe berries of some grape varieties causes theberries to turn red in response; this can be helpfulin identifying the problem early. Full-grownlarvae pupate on the ground or on the leaves, anda second generation of moths becomes active inlate July. This second generation usually is themost injurious. Eggs are laid on the berries, andemerging larvae invade the fruit. Pheromonetraps are available that can help determine periodswhen adult moths are flying and laying eggs. Insecticide applications are suggested forapproximately 10 days after flight periods begin. Concord growers have had good success incontrolling the problem with sprays of carbaryl(Sevin) at those times. Vinifera grape growersshould watch for this problem to determine if theyneed such sprays.

Grape Leafhopper: Although thisdistinctive, orange and white mottled leafhopper isusually encountered at some level in vineyards, itseldom reaches sufficient populations tomaterially damage the vines. The nymphs of thispest suck the juice from the leaves and cause themto become blotched with white spots. Infestedvines may show a lack of vigor. Its droppings areundesirable on table fruit and, if enough stipplingof leaves occurs due to its feeding, the crop couldbe delayed in maturity.

Adult grape leafhoppers overwinterbeneath leaves and trash near vineyards. In Maythe adults migrate to the grapes, feed, and lay eggsjust under the lower leaf surface. After hatching,the young nymphs feed on the leaf undersurfaceand cause the typical leafhopper damage. Therecan be a partial second generation late in thesummer.

Grape leafhoppers are relatively easy tocontrol with insecticides when the nymphs arepresent. These include carbaryl (Sevin),azinphosmethyl (Guthion), methomyl (Lannate)and diazinon. There also are some naturalcontrols (e.g., an Anagrus wasp that parasitizesleafhopper eggs).

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Grape Flea Beetle: These bluish-blackshiny beetles feed on the interior of developingprimary grape buds and, in this way, preventdevelopment of primary grape canes. Theyoverwinter in trashy or wooded areas and emergein the spring to feed and lay eggs on the vines. The eggs hatch to produce light brown larvae thatfeed on the upper leaf surfaces. Mature larvaedrop to the ground to pupate in the soil, and asecond generation of adult beetles emerges in Julyto August.

Control is obtained primarily throughinsecticide applications to kill the feeding larvae. Methoxychlor is labelled for this use on grapes.

MealybugsThe grape mealybug Pseudococcus

maritimus has been identified in vineyards ofwestern Colorado by B.C.Kondratieff and W.Cranshaw (Technical report #TR94-1 Departmentof Entomology, CSU 1994). Populations haveincreased during the last three years and it hasbecome a production threat to vineyards ofwestern Colorado.

Mature, fully grown mealybugs are 3/16of an inch long, pinkish red, covered with a whitepowdery wax. Filaments of wax extend from thesides and rear of the oval, somewhat flattenedbodies. Eggs are yellowish to orange, laid in acottony eggsac under bark or in protectedlocations. Newly hatched nymphs (crawlers) arebrownish and lack the powdery wax cover. Mealybugs overwinter as eggs in their cottonywhite ovisacs, or as young crawlers beneath theloose bark of the vine. In spring the eggs hatchand the crawlers move to the base of the spurs andout onto the new growth. Once mealybugs reachmaturity in mid June most females return to thevine trunk and lay eggs in the protected regionsbeneath the loose bark. The second generationwill hatch a month later and will be responsiblefor a noticeable population explosion. It is thisbrood which will cause the majority of thedamage as well as lay the eggs that willoverwinter.

Vineyard monitoring for mealybug

infestations is important and simple. Mealybugsprefer vigorous vines and can be detected inspring and summer by the presence of honeydewand/or sooty mold on the trunk and below thevine. The presence of honeydew should trigger acloser examination of the vine for eggsacs,crawlers, and adults. In mid-summer, fruitclusters that touch old wood should be examinedclosely for evidence of honeydew, and black sootymold. It s common for mealybug populations toexplode mid-summer and then decline just asrapidly due to the presence of natural predators. Ifcontrol is necessary, it is best achieved with adormant spray which can be followed by asummer treatment. It is important to note thatsummer treatments are only effective if appliedbefore the insects are half grown and their waxycovers are still permeable.

Mealybugs have two generations a year. The first overwinters as eggs or as nymphs; thesecond is produced in mid-summer and, in turn,lays the eggs that constitute the overwinteringgeneration for the next season. In spring theyoung nymphs move to the base of the spurs andthen out onto the green portions of the vine to feedon foliage and fruit. After maturation in earlyJune, most females return to protected areas to layeggs that hatch about a month later (early July). The second or summer generation nymphs thenmove out to the green portions of the vine to feed,and it is primarily this brood that produces thebulk of the fruit damage. As the secondgeneration females mature, some may deposittheir eggs on fruit and leaves; most, however,return to old wood or protected locations to laytheir overwintering eggs.

Achemon Sphinx Moth: Caterpillers ofthe Achemon Sphinx moth have causedoccasional damage to grapes in Colorado. Thelarvae are voracious feeders and can quicklydefoliate sections of a vineyard if large numbersare present.

This pest is related to a better knowncousin, the tomato hornworm. The adults, alsoknown as hawkmoths, approximate the size of ahummingbird and have a similar, darting,

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hovering flight as they fly and feed on flowers atdusk. The achemon sphinx moth has about a 3 to4-inch wingspan, a body and forewings that are amarbled brownish-gray with well-defined darkbrown spots, and hindwings that are a rich rosypink with a brown border and dark spots. Thelarvae are green or reddish, about 2.5 to 3 inchesin length.

Control is rarely needed, but applicationsof Bacillus thuringiensis (Dipel, Biobit,Thuricide) are very effective against sphinx mothif made before the larvae become too large. Otherinsecticides are also effective if applied at earlystages.

Thrips: Thrips are primarily a problemfor table grape production, and then only rarely inColorado. Feeding by western flower thripsduring bloom and early postbloom can result inscarred fruit that is not salable. Feeding by largenumbers on young shoots in the spring can stuntthese shoots and may thus require control.

Thrips are small insects with fringe-likewings (instead of the membranous wings of manyother insects). Adults generally are about 1/16 ofan inch in length and can occur in three colorphases: light, intermediate, and dark. The darkform predominates in early spring while the lightand intermediate forms are most common later. The light form is the most numerous. The twonymphal stages last one to two weeks, duringwhich they feed on both stem and flower or fruittissues. It is this feeding that produces the fruitscarring. Two additional stages (prepseudopupaland pseudopupal) occur in the soil debris. Theemerging adults feed primarily on pollen so far asis known. There are five to seven generations peryear, with a population peak coinciding withgrape bloom. The western flower thrips over-winters in the adult and nymphal stages.

Thrips populations can be determined bycounting adults or nymphs knocked out of theflowers or fruit clusters. Generally, if more than10 adults are observed per cluster, control spraysmay be needed on those cultivars moresusceptible to damage.

Grape Cane Borer: Grape cane borer,

perhaps better known as the branch and twigborer, is at most only a minor pest in Colorado'svineyards; its presence is suspected in FremontCounty, but this has not yet been confirmed byexamination of actual insect specimens. It is awood-boring beetle, Malalqus confertus LeConte,that also attacks other woody plants such as fruitand ornamental trees and shrubs.

On grapes, it derives its common namefrom its method of feeding and the resultingdamage; the adult beetle burrows into weak grapecanes at a crotch or bud axil and proceeds to mineout the woody tissue. This causes shoot wiltingand flagging and, occasionally, partial breakage atthe feeding point when shoot growth reaches 8 to10 inches in length. These broken shoots oftenremain hanging down from the spur afterbreakage. Such wilted or wilted and brokenshoots should be closely examined for anyevidence of feeding holes or, possibly, the feedingadult beetle.

The adult blackish brown beetle is small tomedium sized, 0.3 to 0.6 inches in length,cylindrical in shape with an obviously narrowed"waist" between the abdomen and thorax. Theeggs are smooth, white, and cylindrical with aslightly pointed end. The larvae also are whitish,but covered with fine hair and heavy bodied witha curved "C"-shape that is larger toward the headend. The larvae also can do equally seriousdamage to vines through their feeding on bothdead wood and living tissue; they plug theirfeeding channels with excrement and chewedwood frass.

The eggs are laid singly in cracks andcrevices of the roughened trunk or arm barkduring late spring/early summer (approximatelyMay in Colorado). The larvae emerge two to fourweeks later and establish themselves within thewood of the vine trunk or arms. They feed for thenext 10 months or so, and then burrow toward thetip of the arm (usually in mid-spring) where theyprepare a hollow cell and pupate for one to twoweeks before emerging as adults.

Chemical control can be obtained throughtwo to three applications of carbaryl (e.g., Sevin)

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at seven to ten day intervals when adults areemerging, but this should be considered only as alast resort. Satisfactory control usually isobtained through attention to vineyard and areasanitation. Newly hatched larvae enter dead ordying areas on grape trunks and arms, so much ofthe problem can be controlled by keeping vineshealthy and by removing any dead or dyingportions. Prunings should be collected andburned before bud-break in the spring in order toeliminate overwintering larvae before they pupate. Brush and wood piles should not be allowed toaccumulate near vineyards and also should beburned before mid-March.

Grape Leaf Skeletonizer: Grape leafskeletonizer is reported to occur within Colorado,but damage from this pest is not common. Thebulk of the damage is due to vine defoliation bythe larvae. Under certain conditions, it can feedon the fruit and this injury then leads to bunch rotthat usually destroys the entire fruit cluster.

Adult skeletonizer moths are about 5/8-inch long and have a wingspan of 1 to 1.3 inches,a characteristic bluish-black to greenish-blackcolor, and comb-like bristles along the antennae. The caterpiller larvae are strongly gregarious andhabitually feed side-by-side during their first threeinstars and sometimes in the fourth instar. Thelarvae display a unique swarming behaviour evenat time for the first three molts; they move awayfrom their feeding site (often to an undamagedleaf or to the stem or shoot), form a roundassembled mass, and then molt. The larvaebecome increasingly banded in appearance withsuccessive molts with band colors of brown toblackish purple; body color between the bands isinitially pale brown, but finally a bright yellowjust before the larvae spins its silken cocoon. Thelarvae also have many long, dark hairs on thebody that seem to be poisonous; workers whobrush against the hairs often develop skin weltssimilar to those produced by contact with stingingnettle.

The skeletonizer overwinters in the pupalstage and has two complete (and sometimes athird partial) generations each year. Initial

emergence from overwintering pupae occurs inlate April to mid-May, and the first generationlarvae are usually found in early May to late June. The second generation runs from late June to lateAugust or early September.

Control is readily obtained with chemicalsused for lepidopterous larvae on grapes. Astomach poison, such as cryolite, is preferredbecause of its long residual activity and lowtoxicity to natural enemies. Application ofBacillus thuringiensis (Biobit, Dipel, Thuricide)also gives good control of grape leaf skeletonizerif treatments are properly timed.

Cottony Maple Scale: Scale insects arerarely observed on grapes in Colorado. The onlyspecies observed on grapes here thus far has beenone incidence of cottony maple scale. The mainproblem caused by this pest is the production of agreat quantity of honeydew which, in turn, makesthe grapes sticky and sooty in the same way thatgrape mealybug does.

The adult female cottony maple scale isabout 1/5-inch long, flattened, oval or oblong, apale or dark brown with a large cottony egg sacthat is about two to three times as long as thebody. They could be confused with grapemealybug if care is not taken in examining theinsects. As the scale female continues to lay eggs,the egg sac enlarges; it remains for some timeafter the female has died and the crawlers havedispersed to the undersides of leaves. In late Julyor early August, they mature; the males developwings and mate with the wingless females. Themated females then crawl back to young canes foroverwintering.

Control is best accomplished throughdormant sprays such as those for grape mealybug.

Eight-spotted Forester: Larvae of theeight-spotted forester moth feed on grape leavesand can defoliate vines when quite numerous. Serious injury, however, usually is rare inColorado. Fully grown larvae are about 1 inch inlength and have distinct markings of orange,yellow, black, and white. After feeding iscompleted, larvae drop to the ground to pupate. The adults are black with white and yellow spots

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on the wings.Mites: Mites have not been observed as a

major problem in Colorado vineyards. They dobest in dry, dusty conditions so that raising of dustin the vineyard in mid-summer should be avoided.

The McDaniel and two-spotted mitesoverwinter primarily as adult females in soil andtrash near the base of woody plants. The extent towhich the mites may survive the winter on thetrunk or branches of fruit trees or vines isunknown for western Colorado. It is generallythought that any mites on the trunk migrate downto emerging cover-crop vegetation early in theseason. At this time mite populations exhibit apreference for herbaceous plants and seem toattack fruit plants only secondarily, later in thesummer. Because the two-spotted mite spendshalf the growing season on the cover crop,considerable control can be achieved throughcultural practices such as minimizing oreliminating weeds around and under the vines.

Each adult female produces 40 to 100eggs, and the average adult life span is 15 to 30days but may be up to two months. Unfertilizedfemales produce only male young. Under averagegrowing conditions, probably 10 generations ofmites are produced in a season. As temperaturesbecome cooler in the fall and the days shorter, thefemales turn orange and congregate in branchcrotches and under bark scales. Mite populationsexperience considerable mortality over winter.

The injury caused by mite populations islargely confined to foliage feeding. This feedingcauses collapse of plant cells and loss of vigor inthe vine. When infestations are heavy, the mitepopulations retard fruit color development to suchan extent that fruit quality may be downgraded. High mite populations also can affect budformation.

Nematodes: Nematodes are microscopic,multicellular, unsegmented, parasitic roundworms that live in the soil and feed on roots ofvarious plant species. Some general symptoms ofnematode injury to grapevines are overall vinedecline, yield reduction, weak vigor, greatersensitivity to stress, poor root development, off-

color, and knotted roots. These symptomaticconditions are often confused with water stressand nutrient deficiencies. Unfortunatelynematodes do not cause specific symptoms onabove ground tissues and thus nematode detectionwithout laboratory analyses is impossible. Nematodes can also transmit a variety of viruses(e.g. tomato ringspot virus, grape fan leaf virus).

The following is a list of potentiallydamaging nematode genera found in orchard/vineyard soils of western Colorado (Mesa, Deltacounties). The listed nematodes were identified in1963, 1985 and 1992 by the Colorado AgricultureExperiment Station.Helicotylenchus spp. (the spiral nematode),Meloidogyne spp. (the Root-knot nematode),Paratylenchus spp. (the pin nematode),Pratylenchus spp. (the root lesion nematode),Tylenchorhynchus spp. (the citrus nematode),Xiphinema spp. (the dagger nematode).Currently, none of the above mentioned generahave been specifically connected with decliningvine growth in Colorado vineyards, however poorvine growth could be associated with these multi-host parasitic roundworms.

The intent of this Guide is not to give adescription of the life cycles and associatedsymptomatic injuries of each genera of nematodebut to inform the vineyardist of the problems thatmay occur. Since many vineyard sites inColorado are being planted in orchard ground, itwould be of benefit to get a laboratory analysis ofthe species present and the population levels. Various laboratories throughout California and thenorthwestern states offer a nematode detectionservice.

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Methods for controlling nematodes aremainly limited to resistant rootstocks (see table 3),preplant fumigation and clean nursery stock. Cover crops have been demonstrated to reducenematode population levels. Research trials at theUniversity of California Kearney Field Station hasshown that the cover crop Cahaba white vetchexhibits nematode resistance and nematicidalproperties.

Soil fumigation studies in California havedetermined that the preplant fumigants methyl

bromide and 1,3-D, when properly applied, giveeffective control, but nematode populationsfrequently recolonize quickly followingincomplete fumigations.

It is important to recognize that fumigantsare not only becoming less available (EPAregistrations canceled) but also upset the totalmicroflora and fauna of the soil. The need forwell balanced healthy soil, thus a healthy rootsystem, is significant for wine productivity andlongevity.

Weed ManagementIt is beneficial to take steps to reduce

perennial weed infestations before planting. Thiswill greatly help to control these perennial weedslater. Annual weeds also can be controlled priorto planting if proper steps are taken in thepreparation period.

Most weeds between grape rows can becontrolled by cultivating, disking and mowing;however, weeds in the row are more difficult tomanage. Special hydraulic oes that retract to missthe vines (e.g., Clemons, Weed Badger) can beused to mechanically remove these weeds as canhand hoeing. Most growers, however, prefer thepartial use of chemical herbicides. Severalherbicides are compatible with grapes, includingsoil active types (dichlobenil, diuron,napropamide, oryzalin, simazine, trifluralin) andfoliar active types (glyphosate and paraquat). Allmust be used carefully and in accordance withtheir label requirements.

In Colorado native bindweed is the most commonproblem weed, and in orchards it is usuallymanaged with herbicides containing 2,4D (e.g.,Dacamine, Weedar). This herbicide is NOTREGISTERED for use in vineyards and is verydetrimental to grapes by causing grotesque leafdistortion and reduced growth. Vine death canresult from 2,4-D applications. Spray drift andcontaminated tailwater can cause damage invineyards that have not been sprayed directly.

Glyphosate (Roundup) provides excellentcontrol of weeds in the vine row and can beapplied next to the trunks IF suckers have beenremoved and IF applied before canes droptowards the ground. Vines can be killed if theherbicide is sprayed on green tissue! Duringretraining of damaged vines, special precautionsmust be taken to avoid spraying the shoots atground level.

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Bird ControlBirds of many species (e.g., starlings,

robins, blackbirds, and finches) are attracted toripening grapes. This leads to both crop loss andbunch rot. A flock of 20,000 blackbirds in a twoacre vineyard for 30 minutes can cause verysignificant damage. The problem is severe insmall vineyards and in those with neighboringtrees. There are numerous noise and decoymethods available to keep birds away, forexample, scare eye balloons, mylar reflective tape,plastic bags, electric fencing, recorded distresscalls, 12 volt programmable electronic birddeterents and propane canons. However, the mostreliable method is plastic netting. Plastic birdnetting typically comes in 5,000 ft. rolls that are14 or 17 ft. wide and are 3/4 inch mesh. Theplastic bird netting is draped over an entire

vineyard row (posts, trellis, vines, etc.) and tied. The plastic netting can be virtually a bird-proofenclosure when anchored to the ground orgathered under the vines and tied. the plasticnetting is lightweight (approx. 3 lbs. per 1,000 sq.ft. of 3/4 inch mesh size) and can be applied byhand or by machine. Most growers complainseverely when applying or removing the nettingby hand, expecially if the wind is blowing. Thenetting snags and hangs up on what seems likeeverything in the vineyard (twigs, leaves, posts,wire, your shoes, watch, etc.). Machineapplicators make applying and removing the5,000 ft. X 17 ft. wide rolls an easy task. One rollof 3/4 inch mesh by 5,000 ft. X 17 ft. widetypically costs about $700.00.

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Wine Grape Varieties for Colorado

Variety selection based on your palate isnot good viticultural judgement in Colorado orany wine growing region. Unestablished marketsand unsuitable climates are two very importantreasons worth considering before selecting avariety to plant in Colorado (see table 6, RelativeCold Hardiness of Grapevines Grown inColorado). The climate of a region and particularsite strongly influence the survival, the maturationof grapes and the quality of wines which comefrom them. Planting varieties without establishedmarkets could leave the grower out in the coldwith no home for his crop. Since the 1990 editionof this guide, more wineries have opened and newmarkets established. This increased market hasbeen favorable for some varieties and not so forothers (see Figure 4). Research trials at OMRChave demonstrated several varieties can be grownquite well viticulturally

and enologically. Many of these varieties are ofthe European wine grape species, Vitis viniferawhich is generally recognized as producing thebest wines. Others are hybrids between Vitisvinifera and native American grape species suchas Vitis labrusca, Vitis rupestris, Vitis aestivalis,and Vitis riparia. These hybrids were bred forresistance to disease and pests and for increasedwinter hardiness. Generally hybrids aresomewhat more winter hardy than Vitis viniferavarieties and many bear prolific crops. The winequality of the hybrids is often very good butsometimes is described as lacking a distinctcharacter. Currently, the market for hybrids isextremely limited and most wineries are onlyinterested in Vitis vinifera grapes. All of thevarieties listed below are grown in well drainedmoderately fertile clay loam textured soils.

White Wine Varieties - Vitis viniferaChardonnay. This grape makes the

renowned white wines of Burgundy. It is one ofthe most winter hardy members of V. vinifera andgenerally of the highest commercial value. Chardonnay reaches high sugars (22-24o Brix) inColorado with desirable high acidity (8-10 g/l TA) Currently, Chardonnay is the most widely plantedwine grape in Colorado representing 30% of theentire acreage and has an established market. Chardonnay is an early ripening variety typicallyharvested the first two weeks in September. Mature clusters are small to medium sized (.2 - .4lb.) and amber colored with good sunlightexposure. Chardonnay is a moderately vigorousgrower. The only drawback to Chardonnay is itsslightly earlier budbreak that can result in cropreduction by frost as the variety has poorfruitfulness in secondary buds.

Riesling (White Riesling, JohannisbergRiesling). This major variety of Germany has amedium to hardy winter hardiness rating. Severalvines survived the 1989 freeze of -22oF with

moderate trunk damage. It matures fairly late, butreaches 20-22o Brix in the Grand Valley andusually retains 10 g/l TA. This is a suitablebalance for a wine that can be bottled withresidual sugar. Colorado Riesling is characterizedby its ability to develop the floral bouquets likethose found in German Rieslings. Riesling vinesare moderately vigorous with small to mediumclusters (.15 - .25 lb.). Because it ripens late, thisvariety should be planted in sites with longergrowing seasons. Riesling currently tends tocommand a lower price per ton than Chardonnaywhile yields are comparable.

Pinot blanc. This variety is moderatelyhardy in Colorado and matures early. It is a lowto medium vigor vine that has very desirable sugar: acid balances with potential as a varietal orblended wine. Pinot blanc clusters are small (.2 -.3 pound) and tight and thus subject to occasionalbunch rot. Because of its low - medium vigor thisvariety is well suited for higher density plantings.

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Gewurztraminer. This early ripening,orange-skinned variety is most famous in Alsace,France. It is winter hardy and can bear a largenumber of clusters. Gewurztraminer is a mediumvigor, small (.2 - .35 lb.), tight clustered variety. Picking costs are often higher for this varietybecause of the difficulty removing the shortstemmed clusters. This variety can be harvestedat desirable balances (i.e., 19-20o Brix, 7-8 g/lTA) with careful monitoring of its maturity inSeptember. The variety has shown significantpromise to produce its distinctive aromaticqualities. It tends to command a somewhat higherprice than Riesling.

Muscat blanc (Muscat Canelli). Thisaromatic, early ripening variety has potential to dowell in Colorado although it is less winter hardythan the preceding four varieties. As withGewurztraminer, careful monitoring can allowharvest with sufficient sugar and desirable acidlevels. Muscat blanc is a medium to high vigorvine with medium sized clusters (.40 - 1.00 lb.)and medium-large berries. Presently there arerelatively few producers of the variety in the U. S.although the market is expanding.

Pinot gris. Pinot gris also know as Pinotgrigio in Italy, when ripe is a grayish-rose coloredvariety similar to Gewurztraminer. Pinot grisevolved from Pinot noir and thus retains similarlow to medium vigor growth characteristics. Thesmall clusters (.15 - .25 lb.) ripen early with goodsugar, acid and ph balances. Pinot gris is a newvariety to Colorado that shows good winterhardiness. Although the market potential is notknown the grape is very versatile, and canaccommodate several winemaking styles (i.e.barrel fermentation, malo-lactic, sur lie aging etc.) Pinot gris has an established market in Oregonand is becoming popular in Ohio.

Sauvignon blanc. A popular varietytraditionally blended with Semillon in France tomake a dry dinner wine. Sauvignon blanc is avigorous variety and has a medium winterhardiness level. Sauvignon blanc ripens earlyabout the same time as Chardonnay. The grapeproduces distinct flavors of hay or grass common

in other grape growing regions. Clusters aremedium sized (.2 - .5 lb.). Because of its highervigor, Sauvignon blanc would benefit from alower density planting.

Semillon. Semillon is widely planted inthe Sauterne or Graves region of France where itis used to blend and soften Sauvignon blancwines. Semillon is moderately vigorous andproduces medium to large clusters (.3 - .75 lb.). The berries are large and amber-yellow in colorwhen ripe. Semillon is medium-tender inhardiness. The canes are larger in diameter thanthe others mentioned above. Semillon is slow toleaf out in the spring. This variety would also bemore adapted to a low density planting.

Siegerebe. An aromatic (similar to Muscatblanc), orange-skinned, early maturing varietythat is typically harvested the second week inAugust with low acids of 6-8 g/l TA. Siegerebe isa cross between Gewurztraminer and MadelaineAngevine. This variety is highly susceptible tobird damage. It is not vigorous and thus issuitable for high density plantings. Althoughsomewhat unknown on the market, thismoderately hardy variety could become veryimportant for Colorado.

Rkatsiteli. Rkatsiteli originated in Russiaand Bulgaria. It has a low to moderately vigorousgrowth habit and has performed well in westernColorado. It's upright growth and small diameterreddish canes are distinct. The fruit clusters areloose, slender, small to medium in size (.2 - .4 lb.)and produce wine and floral bouquets similar toRiesling. The berries have an elliptical "football"shape and mature late in the season. Rkatsiteliwould be very adaptable to a high density plantingon a more vigorous site. Rkatsiteli has a medium hardiness level. Availability of this variety is limited.

Muller-thurgau. Muller-thurgau is widelyplanted in Germany and was developed in 1924from a cross of Riesling and Sylvaner at theGeisenheim institute in Germany. The wine is apleasant neutral wine and would be best utilizedfor blending. In Colorado, Muller-thurgauappears less hardy than Riesling. It has a low to

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moderately vigorous growth habit and ripensearlier than Riesling.

Viognier - Nationally, Viognier plantingstotal less than 600 acres. Viognier comes fromthe northern Rhone Valley in France and hasrecently become a popular variety in the US.

Several Colorado growers have planted thisvariety and produced some good wines with finefloral bouquets. The vine has a moderatelyvigorous growth habit and has a medium-tenderhardiness level. It produces good quality fruit andripens during mid-season. The clusters are looseand small - medium (.2 - .4 lb.) in size.

White Wine Varieties -- HybridCultivars

Aurore . A popular hybrid in the easternU. S., it matures very early and is subject to lowacidity unless harvested at fairly low sugar. Wines are fairly neutral and would be betterutilized for blending. It is winter hardy, but notimmune from damage.

Seyval blanc. This hybrid grape has avery vigorous growth habit and is well suited forlow density plantings and improved trellising forbetter canopy management. Seyval produces afresh, crisp wine that is used to blend or withimproved winemaking techniques (oakfermentation, sur lie aging, etc.) made into aricher, longer-lived varietal wine. it is one of themost winter hardy varieties planted in Colorado. Seyval quite frequently needs cluster thinning toachieve high sugars (21-23o brix) and good acids. This medium sized loose clustered variety ripensearly. Seyval would be well adopted to coldersites.

Vidal blanc. This vigorous cultivarappears to be very hardy. The crop ripens late andgenerally retains at least 1 percent TA, which isdifficult to utilize in a dry wine style such as thatfor which the variety is gaining a good reputationin the eastern U. S.

Chardonel. Chardonel, a hybriddeveloped at Cornell University, is a cross ofSeyval blanc and Chardonnay. Chardonel wasdeveloped for its superior wine quality, highproductivity and cold hardiness. Chardonel lookspromising for Colorado. The wine is delicate withlight fruitiness and good body with very littleflavor characteristics of interspecific hybridgrapes. Chardonel has a moderately vigorous

growth habit and its winter hardiness levelappears better than Chardonnay (based on 3 yearsdata). Chardonel breaks bud later thanChardonnay and produces medium sized clusters. Thinning may be necessary during years of goodfruit set.

Cayuga White. Cayuga, also developed atCornell University, was released in 1972 as agrape that would produce a European style whitetable wine. Cayuga is a cross of Seyval and theAmerican species Schuyler. Cayuga grows well inColorado, producing vigorous growth with large(.3 - .85 lb.) loose clusters and big round goldenberries. Cayuga is winter hardy. It is slow tobreak bud but ripens early. This hybrid producesfruity wines that are slightly low in acidity (5-7 g/lTA) but full bodied. Approximately 3 acres arecurrently planted to this promising variety.

Vignoles. Vignoles also know as Ravat 51is widely planted in New York, Ohio and Michigan. Vignoles wines are usually very highin acid and quite often made into a sweet reservedesert style. The growth habit of Vignoles ismoderate and upright. Vignoles ripens very early,the clusters are small, the berries are large andfleshy, not juicy. Vignoles is new to Colorado butappears to be winter hardy and might prove to bea good late harvest style wine.

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Red Wine Varieties - V. Vinifera Merlot. The Merlot grape produces one of thebest wines from Colorado and is the second mostwidely planted grape in Colorado representing18% of the entire acreage. In most years,Colorado Merlots are deep colored, very fruityand full bodied. It is often used as a blend to forma soft velvet-like quality to the finish of wines thatmight otherwise be harsh. Merlot has a moderategrowth habit and is medium tender in hardiness. It has small to medium (.2 - .4 lb) clusters that areloose to well-filled and have long stems. Handharvesting goes quickly as stems are easily cut. Merlot ripens fairly early and can achieveexcellent sugar acid balances (24o brix, 8 g/l TA). Merlot has an established market in Colorado andcontinues to be popular with winemakers.

Cabernet Sauvignon. The cool nights ofColorado and late-season ripening characteristicsof this variety tend to produce outstanding colorretention and an excellent balance of sugar, acidand Ph. This leads to a well-proportioned, full-bodied wine. It's winter hardiness level is equiva-lent to that of Merlot, its traditional blendingpartner. This variety has a vigorous growth habitand small to medium (.2 - .4 lb.) conical shapedloose clusters. It is very easy to pick and becauseof its late ripening would be a candidate forplanting in sites with longer growing seasons.

Pinot noir. This variety, one of thefamous red Burgundies, is mentioned because it isgenerally considered to be the most winter hardyred variety. Pinot noir is a low vigor vine withsmall tight-filled clusters (.1 - .2 lb.). This varietyadapts well to high density plantings. Unfortunately it has yet to demonstrate an abilityto develop adequate color and character inColorado. One should not rule it out with futureexperience; however, at this time the variety isbest suited to sparkling cuvee' or blanc d'Noirwine styles.

Lemberger. This loose-clustered dark pigmented variety shows promise for Coloradowith very favorable sugar, acid and Ph parameters. It is increasingly popular in Washington state andhas moderately high winter hardiness under

normal Colorado conditions. Unfortunately, cleanvirus free Lemberger stock is unavailable and thisshould be considered before planting.

Cabernet franc. Cabernet franc isbecoming popular with Colorado winemakers as ablending wine. The wine is similar to Cabernetsauvignon yet softer and more subtle and retainsthe distinctive Cabernet aroma. Cabernet francdoes not develop deep skin color. It has amoderately vigorous growth habit and appearsslightly more winter hardy than Cabernetsauvignon. The clusters are loose filled and smallto medium (.2 - .4 lb.) in size. It ripens later thanMerlot but earlier than Cabernet sauvignon. Atharvest clusters often appear immature because ofthe poor skin color, however fruit compositionsachieve excellent balances. Cabernet franc is wellknow in the scientific community as a sensitiveindicator plant for diagnosing leafroll virus. When inoculated with the virus, it visiblyexpresses symptoms (red leaves, green veins)much more profoundly than other varieties.

Sangiovese. This vigorous variety is oneof the most widely planted grapes in Italy where itis a major component of Chianti wines. Sangiovese is new to Colorado and its becomingquite trendy in California. This variety ripensvery late in Colorado and produces light coloredfresh fruity wines. The clusters are large andloose filled with light red-colored large berries. Hardiness levels (based on 3 years data) appearequivalent to Merlot. The vines produce heavycrops that may require cluster thinning to achievesugars of 20-22o brix. Sangiovese would be amatch for a low density planting on sites with thelongest growing season.

Shiraz-Syrah. Syrah is a very darkskinned grape that ripens late and in Coloradoproduces wines with good acid, color and tannins. The clusters are long, loose-filled and conical inshape weighing about (.2 -.45 lb.) each. Thehardiness level of this moderately vigorous varietyis similar to Merlot and Cabernet. Syrah, alsoknown as Shiraz in Australia would be well suitedfor the warmest sites with a longer growingseason.

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Red Wine Varieties - Hybrid Cultivars

Chancellor. Also known as Seibel 7053,produces relatively full-bodied wines, is a loose-filled clustered variety that ripens mid season. Itis a medium hardy variety.

Rougeon. A very hardy variety thatproduces an early well-balanced crop withexcellent color. The loose-filled clusters aremedium sized (0.35 lb.) and the berries are blue-black in color. This variety survived the 1989freeze of -22oF with little trunk damage.

Dechaunac. Also known as Siebel 9549,is very prolific, colors very early, but ripens lateseason and may require thinning to mature thefruit. This variety is extremely hardy, survivingthe 1989 freeze of -22oF with no cane or trunkdamage and very little latent bud damage. Thisvariety can produce up to 60 lbs./vine and shouldbe considered for low density plantings.

Norton/Cynthiana. Norton also known asCynthiana produces very good wine with a deepblue-black red color. The small to mediumclustered high acid variety was first discovered byDr. D.N. Norton of Virginia. Norton is anAmerican species Vitis aestivalis and is verywinter hardy. It's canes are very red in color withsmall buds. Norton blooms late and appears tohave medium vigor.

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Table 6.

Relative Cold Hardiness1 of Grapevines Grown In Colorado

Very Hardy Hardy Medium Medium Tender

Concord Aurore Cabernet franc Cabernet Sauvignon

De Chaunac Baco noir Chancellor French Columbard

Niagara Cayuga Chardonnay Merlot

Norton/Cynthiana Chardonel Dolcetto2 Muscat blanc

Rougeon Delaware Gewurztraminer Sangiovese

Foch Lemberger Sauvignon blanc

Seyval blanc Pinot blanc Semillon

Pinot gris Shiraz

Pinot noir Viognier

Riesling

Rkatsiteli

Siegerebe

1Hardiness is based on visual assessment and differential thermal analysis of vines grown in adeep clay loam soil at Orchard Mesa Research Center.2Dolcetto is grafted to 1616 couderc rootstock.

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Table Grape Varieties

Successful table grape cultivation in Colo-rado requires optimum cultural practices; but,with certain considerations, they can be grownwith the same management skills as wine grapes. The intent of this section in the Colorado GrapeGrower's Guide is to provide the grower withadditional information for table grapes that hasnot been addressed previously in the text.

Varietal selection is extremely importantand involves considerations of winter hardinessand marketability. Information concerning per-formance of specific cultivars in Colorado islimited although some information does exist. Asummary of vegetative growth and fruit character-istics for 15 of the most popular seedless tablegrape cultivars that are currently available isprovided in Tables 7 and 8. The followingdescriptions are of several varieties grown atOrchard Mesa Research Center that appear wellsuited for the wine grape growing regions ofColorado.

Himrod . This white variety is a crossbetween Ontario X Sultanina (ThompsonSeedless) and has excellent quality fruit which isjuicy and sweet with pleasant flavor. Thisvigorous vine is moderately hardy; it survived the1989 freeze of -22oF with little trunk damage. Himrod tends to shed individual berries whenpicked; this should be considered before plantinglarge acreages.

Interlaken . A second white variety that isalso a cross between Ontario X Sultanina. Thisvigorous vine bears heavy crops early in theseason, has good flavor and is somewhat lesshardy than Himrod.

Lakemont. A third white variety of thesame parentage as Interlaken (Ontario X Sultanin-a). It produces large compact clusters with qualitythat approaches that of Himrod and ripens a weekor two later. It has moderate to low winter har-diness.

Suffolk Red. A large-berried, red seedlessgrape with good quality. It has low winter

hardiness and sets loose clusters. It survived theeight winters prior to 1989, but was winter killedto ground level by the -22oF temperatures duringJanuary of 1989.

Other seedless varieties (e.g., ConcordSeedless, Thompson Seedless, Flame Seedless)have been tested at OMRC. However, theirperformance has been poor and they cannot berecommended for commercial production. Thereare many seeded varieties (e.g., Concord, Niagra,Steuben, Golden Muscat, etc.) that can be suc-cessfully cultivated in Colorado; all have moreintense marketing challenges when competingwith the more desirable seedless varieties.

Pruning and improving grape quality aretwo additional areas that should be modified fromwine grape production. Pruning and training tablegrapes depends on variety and the overall objec-tive of the operation. Pruning and training tablegrapes can be identical to that of wine grapes, butoften should be modified to help equalizeproduction for large average crops of high-qualityfruit. Most varieties mentioned above are vigo-rous and should be trained to a pruning systemthat allows for that vigor such as the GenevaDouble Curtain, Four Arm Kniffen and/orUmbrella Kniffen. These systems require moretrellis expense but may be better suited for themore vigorous varieties.

Quality of table grapes can be improvedby blossom thinning (i.e., removal of flowerclusters before bloom and of immature clusters), acultural practice not typically performed on winegrapes. Like pruning, thinning concentrates theactivities of the vine into the remaining parts andstrengthens the vine by limiting the crop withoutdiminishing the leaf area. Girdling, also calledringing, is an old practice that improves set, in-creases size of berries and advances maturation; itshould NOT be performed in Colorado due to theincreased risk of Crown Gall infection.

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Table 7. Vegetative growth characteristics of seedless table grape cultivars.

Ripening Vine Yields/ WinterVariety Season Vigor Vine Hardiness

Canadice Early Medium High High

Challenger Mid Season Medium Medium Medium

Concord Seedless Late Mid Medium Low High

Glenora Mid Season Medium Low Low

Himrod Early Medium Low Medium

Interlaken Very Early Medium Medium Low

Lakemont Mid Season High High Low

Mars Early Medium Medium Medium

NY 63878.1 Mid Season Medium High Medium

Reliance Early High Medium High

Remaily Late Mid Medium High Low

Romulus Late Medium Medium Medium

Suffolk Red Mid Season High Low Low

Vanessa Mid Season Medium Medium High

Venus Very Early High High Medium

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Table 8. Fruit characteristics of seedless table grape cultivars.

Berry Cluster ClusterVariety Color Flavor Size Size Compactness

Canadice Red Good Medium Medium Tight

Challenger Red Good Large Medium Loose

ConcordSeedless Blue Fair Small Small Loose

Glenora Blue Good Medium Medium Compact

Himrod White Excellent Medium Medium Loose

Interlaken White Good Medium Medium Compact

Lakemont White Good Medium Large Compact

Mars Red Good Medium Small Compact

NY 63878.1 Red Excellent Medium Medium Compact

Reliance Red Good Medium Medium Loose

Remaily White Fair Large Large Compact

Romulus White Fair Small Large Compact

Suffolk Red Red Excellent Large Medium Loose

Vanessa Red Good Medium Medium Compact

Venus Blue Good Large Large Tight

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Vine Sources (1995)

In the United States there are hundreds of grapevine nurseries and thousands of retail outlets forgrapevines. The following is a representative sample of suppliers from coast to coast that have good varietalselection and certified stock availability.

Arroyo Seco Vineyards Inc. (V)P. O. Box 395Greenfield, CA 93927408-674-2318

Bien Nacido Vineyards (V)1253 Coast Village Road, Suite 102Santa Barbara, CA 93108-3790805-969-5803

Borri Nurseries Inc. (V)1150 Felta RoadHealdsburg, CA 95448707-433-6045

Concord Nurseries Inc. (A, FH, V)10175 Mile Block RoadNorth Collins, NY 14111-9770716-337-2485

Duarte Nursery, Inc. (V)1555 Baldwin RoadHughson, CA 95326209-531-03511-800-GRAFTED

Fairacre Nursery (A, FH, V)Rt. 1, Box 1068Prosser, WA 99350-9788509-786-2974

FPMS* (V)Foundation Plant Materials ServiceUniversity of CaliforniaDavis, CA 95616916-752-3590

Ge-No's Nursery (V)8868 Rd. 28Madera, CA 93637209-674-4752

Grafted Grape Vine Nursery (A, FH, V)2399 Wheat Rd.Clifton Springs, NY 14432315-462-3288

Inland Desert Certified Grape Nursery (V)Route 1, Box 1315Benton City, WA 99320509-588-3405

Meyer Orchards & Nursery (V)3785 Gibson Rd., NW.Salem, OR 97304503-364-3076

Sonoma Grapevines Inc. (V)1919 Dennis LaneSanta Rosa, CA 95403707-542-5510

The codes after the source name show whether they carry Vinifera varieties (V), French-AmericanHybrids (FH), or American varieties (A).

FPMS is a service unit created to provide virus-indexed plant materials for research and commercialuse. Private individuals or companies can contract with FPMS on a fee-for-service basis to have specialgrape varietal selections heat treated and virus tested as necessary to qualify them for Foundation stockstatus. Contracts and fee schedules are available from FPMS upon request.

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Sources for Vineyard Supplies

A. M. Leonard, Inc.P.O. Box 816Piqua, Ohio 453561-800-543-0633

Horticultural and Viticultural tools

Barnel International, Inc.1075 NW Murray Rd., Suite 256Portland, OR 972291-800-877-9907

Horticultural and Viticultural tools.

Fruita Cooperative1650 U.S. Highway 6 & 50Fruita, CO 81521970-858-3667

Fertilizer

Grand Junction Pipe & Supply2868 Highway 6 & 24Grand Junction, CO 81501970-243-4604

Irrigation piping and supplies

Munroe Pump735 South 9thGrand Junction, CO 81501970-242-6810

Pumps

Orchard Valley SupplyVineyard & Orchard SupplyRoute 1, Box 41-BFawn Grove, PA 17321Phone: 717-382-4612FAX: 717-382-4612

Complete vineyard materials, supplies andequipment.

Rears Manufacturing Co.2140 Priarie Rd.Eugene, OR 974021-800-547-8925

Vineyard equipment

T. G. Schmeiser Co.Box 1047Fresno, CA 937141-209-268-8128

Vineyard drill, Till and Pak, Culti-Plow, andland levelers.

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The Grower Supply Center2415 Hartford RoadFallston, MD 21407410-931-3111

Complete vineyard materials, supplies, andequipment.

United Fruit Growers144 Kluge Ave.Palisade, CO 81526970-464-5671

Pruning equipment, fertilizer, insecticides,hand tools.

Waterford Corporation404 N. Link LaneBox 1513Fort Collins, CO 80522970-482-0911

Trellis supplies and installation.

Western Implement2919 North AvenueGrand Junction, CO 81501970-242-7960

Tractors, implements, hand tools, posts, wire,etc.

Wildlife Control Technology Inc. Bird netting2501 N. Sunnyside Ave #103Fresno, CA 937271-800-235-0262

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Vineyard Development and Production Cost Assumptions

Projecting the true costs of establishing ormaintaining a vineyard is extremely difficult. This is particularly true in the case of smallacreages where various compromises can be madeto trade labor costs for equipment costs. Manyexperienced growers, researchers, extension staff,consultants, and retailers were involved in thefollowing cost estimate study. A number of broadassumptions were made to provide a commonbasis for these costs. First, we assumed that wewere establishing a new vineyard on open groundwith no improvements. All prices for capitalimprovements and equipment are new and in 1996dollar values. Next, we assumed that certifiedvirus free #1 self rooted Chardonnay vines or asimilar variety were planted with a production lifeexpectancy of 30 years following a four yearestablishment period. The sample vineyard isplanted at a density of 871 vines per acre. Thespacing is 5 feet between vines and 10 feet be-tween rows. The trellis system is a six wirevertical shoot positioned system with one stake ateach vine and 4 inch by 8 foot line posts every 30feet. The traditional 3 post H-brace system wasused at both ends of every row for anchoring thetrellis.

We assumed that labor used in wine grapeestablishment and production is valued at

$8.00 per hour. This wage rate is determined asthe net cost to growers for hired labor which ispaid a cash wage of $6.00 per hour with an addi-tional $2.00 per hour for payroll expenses (socialsecurity, taxes, workmens compensationinsurance, withholding taxes, record keeping,etc.). The cost of an irrigation system can varywidely -- from $500 for a gated pipe system to$1500 / acre for an automated, microsprinkler orpressure compensating emitter system. Theautomated drip irrigation system itemized is basedon a horizontal stainless steel sand media filterwith automatic backflush, a centrifical sandseparator, a flow meter, a computerized controllerand a chemical injector.

Weed control costs are shown using a in the rowhydraulic grape hoe. In addition to mechanicalcultivation, herbicide application such asglyphosate was figured for controlling thepersistent bindweed. The production costs areshown on a per acre basis (Table 10) and assume ayield of 4 tons per acre.

These general assumptions were used to developthe vineyard establishment and production coststhat follow. The example cost sheets (Tables 9and 10) are intended to itemize the major costfactors and indicate their relative importance.

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Table 9. Vineyard establishment costs: Mesa County, Colorado, 1996, includes new equipment, dripirrigation, 6 wire vertical shoot positioned trellis and 1 metal stake per vine.

Item 10 Acres EquipmentTractor (40 HP) 20,000.Truck (3/4 ton) 17,000.Sprayer (200 gal vineyard airblast) 8,000.Weed Sprayer (100 gal) 2,000.Trailer 1,000.Disk 3,000.Hydraulic grape hoe (Clemons, badger, etc.) 4,000.Chopper 1,500.Auger 1,500.7' Blade 800.Springtooth 1,200.Shop tools 2,500.Pruning Shears 80.Misc. Equipment (staples, strainers, tie tape etc.) 1,000.

$63,580.

Capital ImprovementsShop & Storage Building (33' x 45' metal building) 9,000.Irrigation System (automatic, drip), @ $1,500/A 15,000.5' Grape Stakes, steel epoxy coated 16 gauge, 871/A @ 1.40 ea. 12,194.Treated Posts, 4" x 8' and 4" x 10' 200/A @ 6.25/post 12,500.Wire 12.5 gauge high tensile, 4000' roll (12 rolls/A) 6 wire trellis 7,800.1 yr, #1 self rooted cuttings, 871/A @ $.80/vine 6,968.

$63,462.

Overhead, Labor ($8/hour) & MaterialsLayout & Mark, (5 Hr/A) + $50 rental 450.Preplant weed control, (1 Hr + $70 material) /A 780.Preplant Land Prep., chisel, plow, disk 2X, float, $135/A 1,350.Post Driving, $2/post @ 200 posts/A 4,000.Trim & plant @ 21 Hr/A 1,680.String wires, staple & set stakes @ 40 Hr/A 3,200.Train and Prune @ 25 Hr/A-2nd yr + 12 Hr/A-3rd yr 2,960.Cultivate, 5X @ 4 Hr/A (all years) 1,600.Mildew Control, 4X @ (1 Hr + $16 material) /A 960.Fuel and Repair, $90/A/yr all years 900.Water and Taxes, $55/A/yr 550.

$18,430.

TOTAL $145,476. Per Acre $14,547.

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Table 10. Estimated annual per acre vineyard production costs.1 (5 x 10 spacing, 871 vines/A)

Item Detail (per Acre) Cost/Acre

Fuel and Repair $90 $ 90.00

Water & Taxes $55 55.00

Mildew Control 6X @ (1 Hr + $16 mat.) 144.00

Herbicide 1X @ (2 Hr + $60 mat.) 76.00

Pruning $.22/vine 192.00

Brush disposal 1 Hr 8.00

Canopy positioning 8 Hr 64.00

Suckering 6 Hr 48.00

Mechanical weed control (Hydraulic hoe) 5X @ 2 Hr ea. 80.00

Irrigate .5 Hr/week (4 months) 64.00

Picking $94/ton 376.00

Fertilizer, Ammonium Sulfate + micronutrients 50.00

Cultivate, mowing/discing 3 X @ 1.5 Hr each 36.00

Miscellaneous Labor & Supplies 50.00

TOTAL per acre $ 1,333.00

1Based on 1996 data and labor costs of $8.00 per hour.

80

Useful Books and Publications

Below is a list of books and publications that growers should consult as additional backgroundreference material to the Colorado Grape Growers Guide.

General ReferencesFrom Vines to Wines. 1985. J. Cox. Garden Way Publishing, Pownal, VT. 253 pp.

General Viticulture. 1974. A. J. Winkler, J. A. Cook, W. M. Kliewer, and L. A. Lider. Univ. of Calif.Press, Berkeley. 710 pp.

Grape Growing. 1976. R. J. Weaver. John Wiley & Sons, Inc., New York. 371 pp.

Grape and Wine Production in the Four Corners Region. 1980. E. A. Mielke, et. al. TechnicalBulletin No. 239, University of Arizona. 116 pp.

Grape Production in Colorado: An Evaluation of Grape Varieties for Wine Production and of GrapeProduction Risks and Profit Potentials. 1985. R. Hamman and R. Renquist. Report prepared for theColo. Dept. of Agric. 12 pp.

Knowing and Making Wine. 1981. Emile Peynavd. John Wiley & Sons Inc., New York, NY. 391 pp.

The New Frank Schoonmaker Encyclopedia of Wine. 1988. Alexis Bespaloff. William Morrow andCompany, Inc., New York, nY. 624 pp.

Oregon Winegrape Growers Guide, 4th Edition 1992. Ted Casteel. The Oregon WinegrowersAssociation, 1200 NW Front Avenue, Suite 400, Portland, Oregon 97209. 258 pp.

Proceedings of the Second International Symposium for Cool Climate Viticulture and Oenology. 1988. New Zealand Soc. for Viticulture and Oenology, Auckland, New Zealand. 365 pp.

The Production of Grapes and Wine in Cool Climates. 1987. David Jackson and Danny Schuster. Butterworths of New Zealand. 192 pp.

Rootstock Seminar, A Worldwide Perspective. 1992. Proceedings American Society for Enology andViticulture, June 1992. Reno, Nevada. 84 pp.

Sunlight into Wine, A Handbook for Winegrape Canopy management. 1991. Richard Smart & MikeRobinson. Wine titles, Australian Industrial Publishers Pty. Ltd. 88 pp.

Viticulture Volume 2 Practices. 1992. Coombe, B. G. and P. R. Dry. Winetitles 2 Wilford Avenue,Underdale SA 5032 Australia. 376 pp.

81

Frost & Winter Hardiness/InjuryMinimizing Winter Damage: Site selection, vineyard establishment, and maintenance. 1979. W. Wolfe. Proc. Wash. St. Grape Society. 9:67-75.

Pruning Effects on Cold Hardiness and Water Content During Deacclimation of Merlot Bud and CaneTissues. 1990. R. A. Hamman Jr., A. R. Renquist, and H. G. Hughes. Am. J. Enol. Vitic. 41(3):251-260.

Seasonal Carbohydrate Changes and Cold Hardiness of Chardonnay and Riesling Grapevines. 1996. R.A. Hamman, Jr., I. E. Dami, T. M. Walsh, and C. Stushnoff. Am. J. Enol. Vitic. 47(1): (in press).

Vine Hardiness: A part of the problem of hardiness to cold in N.Y. vineyards. 1971. N. Shaulis. Proc.New York St. Hort. Soc. 116:158-167.

Wine Grape Performance of 32 Cultivars in Western Colorado 1982-1986. 1993. R. A. Hamman Jr. Fruit Varieties Journal 47(1):59-63.

Pest ManagementCompendium of Grape Diseases. 1988. R. C. Pearson and A. C. Goheen, eds. APS Press, The Am.Phytopath. Society, 3340 Pilot Knob Road, St. Paul, Minnesota, 55121. 93 pp. [Cost $20.00]

Grape Pest Management. Revised 1991. D. L. Flaherty, et. al., eds. Pub. No. 3343. Div. of Agric.Sci., Univ. of Calif. 416 pp.

Insect and Mite Pests Associated with West Slope Wine Grapes. 1994. B. C. Kondratieff & W.Cranshaw. Technical Report TR94-1. Agricultural Experiment Station, Colorado State University. 12pp.

Phylloxera Issue. 1990. B. Strik, ed. The Wine Advisory Board Research Report (Special Report)Special Issue (Sept.): 1-17. Published jointly by the [Oregon] Wine Advisory Board and Oregon StateUniv. Ext. Service, Corvallis, OR. 17 pp. (+ 4 pp. insert with color photos.)

Vineyard Pest Management: Alternatives for the future. 1992. Publication compiled for the AmericanSociety for Enology and Viticulture workshop May 1992. Napa Valley. 33 pp.

Economic/Cost AnalysesCost Analysis of Selected Wine Grape Vineyard Production Practices in Washington. 1983. D. Kirpes,R. Folwell, and M. Ahmedulla. EB 1200. Wash. St. Univ. Coop. Ext., Pullman, WA. 16 pp. [Cost$0.50]

The Economics of Establishing and Operating a Concord Grape Vineyard. 1990. J. G. Schimmel, R. J.Folwell, and R. Wample. EB1572. Wash. St. Univ. Coop. Ext., Pullman, WA. 10 pp (+ 13 tables). [Cost $0.50]

Wine Grape Vineyard Development in Washington and Economic Perspectives. 1986. S. Lutz, R.Folwell, M. A. Castaldi. EB 1398. Wash. St. Univ. Coop. Ext., Pullman, WA. 56 pp. [Cost $1.25]

82

Viticulture Trade Magazines

Grape GrowerPublished monthly, Munford Publications, Inc.,4974 E. Clinton Way, Suite 123, Fresno, CA93726-1558, 209-252-7000

Practical Winery & VineyardPublished bimonthly, 15 Grand Paseo, SanRafael, CA 94903, 415-479-5819

Vineyard & Winery ManagementPublished bimonthly, J. William MoffettBox 231, Watkins Glen, NY 14891607-535-7133

The Wine SpectatorPublished biweekly, M. ShankenCommunications, Inc.Opera Plaza, Suite 2040, 601 Van Ness Ave., SanFrancisco, CA 941021-800-752-7799

Wines & VinesPublished monthly, The Hiaring Company1800 Lincoln Ave., San Rafael, CA 94901-1298415-453-9700

Wine Business Monthly867 W. Napa St, Sonoma, CA 95476707-939-0822707-939-0833 (Fax)

Grape and Wine Resources on theInternet

1. U. C. Davishttp://pubweb.ucdavis.edu/Documents/wine/venl.html

2. Food Science & Technology Departmenthttp://aruba.nysaes.cornell.edu/fst

3. The Wine Research & Extension at Cornellhttp://aruba.nysaes.cornell.edu:/FST/MARKET/wineries.html

4. All About Winehttp://www.aawine.com/index2.html

5. CSIRO Grapevinehttp://cgswww.adl.hort.CSIRO.au/

6. Virtual Vineyardshttp://www.virtualvin.com

7. Not Just Cows List of Agricultural List Servershttp://www.lib.lsu.edu/sci/njc.html#1 listserv

8. What is Sustainable Agriculturehttp://www.sarep.ucdavis.edu/sarep/concept.html

9. Organically-Grown Grapeshttp://www.fetzer.com/

10. Wine Business Monthlyhttp://smartwine.com

11. Wine Wizardshttp://www.wines.com

Figure 6. Seven wire vertical shoot positioned trellis, Cordon training.