growing grapes in wisconsin (a1656) - cooperative extension...the well-known concord grape, for...

T E R Y L R . R O P E R , D A N I E L L . M A H R , PA T R I C I A S . M C M A N U S , B R I A N R . S M I T H

GROWING GRAPESIN WISCONSIN

A1656

Vitis labrusca

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CONTENTS

The grape plant . . . . . . . . . . . . . . . . . . . . 2

Site selection and soil preparation . . . . . . . . 3

Cultivar selection . . . . . . . . . . . . . . . . . . 3

Planting stock and propagation . . . . . . . . . . 6

Planting design and row spacing . . . . . . . . . 6

Planting . . . . . . . . . . . . . . . . . . . . . . . . 7

Soil management and weed control . . . . . . . . 7

Fertilization . . . . . . . . . . . . . . . . . . . . . . 8

Flowering and fruit set . . . . . . . . . . . . . . . 8

Harvesting and storage . . . . . . . . . . . . . . . 8

Trellis construction . . . . . . . . . . . . . . . . . 9

Training and pruning . . . . . . . . . . . . . . . 11

Managing grapevines in cold climates . . . . . 15

Insect pests . . . . . . . . . . . . . . . . . . . . . 16

Diseases . . . . . . . . . . . . . . . . . . . . . . . 18

Problem solving . . . . . . . . . . . . . . . . . . 23

Glossary . . . . . . . . . . . . . . . . . . . . . . . 25

Related publications . . . . . . . . . . . back cover

Nurseries . . . . . . . . . . . . . . . . . back cover

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THE GRAPE PLANTThe grape is a woody perennial vine. Perennialportions of the plant include the roots, trunk, andperhaps cordons. Fruit are produced on currentseason’s shoots. These shoots arise from com-pound buds that are produced at a leaf base oraxil a year earlier. The compound bud must sur-vive the winter to produce fruit and vegetativegrowth the following year. After leaf fall the dor-mant primary shoot is called a cane.

The compound bud is really one large bud sur-rounded by two to five smaller buds. These are allenclosed in one set of bud scales. If frost kills thelarge bud of the group in the spring, a second budmay produce a smaller crop of fruit. If both theprimary and secondary bud are injured or killed,vegetative growth can still continue from one ofthe smaller buds, but no fruit will be produced. Inthis case vegetative growth may be excessive asall of the strength of the vine is channeled intovegetative growth.

The most common cultivated grapes in Wisconsinare the American types (Vitis labrusca). MostAmerican grapes are hardy throughoutWisconsin. For the crop to mature, select early-maturing cultivars. American grapes typicallyproduce two to four flower clusters per shoot, onshoots produced at the second to fifth node fromthe cane base. To retain productive flower clus-ters, leave fewer longer canes at pruning.

French hybrid types can be grown in protectedsites in southern Wisconsin. These types producefruit on shoots that arise from the first to thirdnodes from the base of the cane. To obtain goodyields from these vines, leave more shorter caneswhen pruning.

Wild American grape vines are found throughoutWisconsin. Some wild grape vines produce satis-factory fruit. Some wild grapes are dioecious,meaning they have separate male and femaleplants. Male plants will never produce fruit.They can be identified at blossom by the absenceof a stigma, style, and ovary in the flowers. Withthese exceptions, the male and female plants areidentical.

Grapes , one of the oldestcultivated plants in the world, can grow in all butnorthernmost Wisconsin. However, success depends on

using adapted cultivars (cultivated varieties), choosing anideal site, and carefully following proven cultural practices.

While grapes are a good crop for home use or limited local cashmarkets, they are a risky commercial crop. Periodically, harsh

Wisconsin winters will substantially injure vines, ending production for one ormore seasons. Spring frosts or freezes frequently damage new growth. The hardiest cultivarsusually regrow rapidly after winter or spring injury, but other cultivars may be completelykilled. Vitis vinifera grapes, which are used for wine production, are not hardy in Wisconsin.

GrapesI N W I S C O N S I N

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The grape vine must be supported. A post, wall,fence, trellis, or arbor are all satisfactory. Supportkeeps the plant at working height and mostimportantly spreads the growth so that moreleaves are exposed to sunlight. It also improvesaeration and makes insect control easier. Yieldsshould range from 5 to 30 pounds of fruit pervine or 2 to 8 tons per acre depending on site,cultivar, and management expertise.

SITE SELECTION ANDPREPARATIONSince grapes are a perennial crop, the vines can’teasily be moved once they are planted. Site selec-tion and preparation are particularly important.Soil preparation should begin the season beforeplanting. Planning ahead allows time to adjustthe soil pH, control perennial weeds, and amendthe soil.

When selecting a site, consider space require-ments. Grapes grown on a trellis occupy wide,shallow spaces. Allow 10 to 14 feet of trellis spaceper vine. As the canes grow in the summer theywill fill out 2 to 3 feet on either side of the trellis.

The ideal site for grapevines is on gently slopingland that will allow cold air to drain into adjacentlower areas. Southern exposures with a gentleslope are ideal. The bottoms of valleys are “frostpockets” and may be several degrees colder thanadjacent hillsides. Hilltops are undesirable asthey may be windy, but the wind can be tem-pered with windbreaks. Grapes grow best insandy or gravelly loam soils, but they will growin all but the rockiest or heaviest clay soils.Grapes will not survive long on heavy clay soilswith poor internal drainage. Sandy soils mayhave difficulty retaining moisture and nutrients.Tiling to improve drainage is rarely justified forgrapes. Grapes do best in sunny locations andwill not thrive in shade.

The first step in soil preparation is amending thesoil. To determine soil nutrient needs, submit asample for testing. Sample to a depth of 6 inches.For information on how to collect representative

samples and where to send them, see Extensionpublication Sampling Lawn and Garden Soils forSoil Testing (A2166). Follow soil test recommenda-tions to adjust the pH to a level between 6 and 7.Add fertilizer if called for in the soil test. Grapesoils should have 25 ppm available phosphorusand 100 ppm available potassium. To improvesoil tilth, aeration and water holding capacity,add and incorporate organic matter such asmanure, compost, or green manure crops.

The season before planting is also the best time tocontrol perennial weeds such as quackgrass andCanada thistle. Use a non-residual systemic her-bicide or tillage to control these weeds. If a hard-pan is present, till to a depth of 18 inches in per-pendicular directions.

For large plantings, seed the area to perennial ryein the late summer so it will establish a turfbefore winter. This will prevent erosion duringthe winter and will facilitate planting in thespring by creating a firm surface. If possible, layout the rows in the late fall and kill the sod in theplanting strips to a width of about 3 to 4 feet.

CULTIVAR SELECTIONChoosing grape cultivars for Wisconsin is a com-promise of hardiness, early maturing fruit, andthe quality and flavor of the grape. Of the hun-dreds of grape cultivars available, many willgrow in Wisconsin but only a few are consistentlyproductive in Wisconsin’s rigorous climate.

The well-known Concord grape, for example,will grow and produce fruit in Wisconsin, butrequires a 155- to 160-day growing season for thefruit to ripen. Concord will ripen to best qualityonly in southern Wisconsin and only two or threeyears out of every five. Concord vines and shootsare injured at temperatures below –20°F.

The following cultivars are recommended forgrowing in Wisconsin in the zones indicated infigure 1. Cultivars of each type are listed in orderof ripening. The more hardy American types aremost likely to be successful. French hybrid typesare suggested for trial plantings only.


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A MERICAN GRAPES

Blue- or black-fruitedcultivarsBuffalo Zone 5bOne of the best American grapes.Excellent for table use or juice.Medium to large, well-filled clus-ters with medium-sized berries.Spicy sweet melting, nonfoxy fla-vor. Vigorous, disease-resistantvine. Ripens early September. Caneprune.

Valiant Zone 3aMedium-sized, tart fruit in smallclusters. Used primarily for jamsand jellies. Plant is vigorous, veryhardy, and productive. Ripens earlySeptember. Hardier than Beta. Caneprune.

Bluebell Zone 4aAttractive, dark blue berries aremedium to large; slipskin type.Juicy with a pleasant fresh flavor.Makes an excellent jelly and lightred juice. Ripens early to mid-September. Very hardy. Caneprune.

Beta Zone 3bHardy, vigorous, disease resistant,productive. Small, tart fruit is bestsuited for jelly. Ripens mid- to lateSeptember. Cane prune.

Fredonia Zone 4bMedium to large fruit with excel-lent flavor. Used to make a high-quality, unfermented juice. Plant isvigorous and moderately produc-tive. Susceptible to downy mildew.Ripens mid-September. Caneprune.

St. Croix Zone 4bMedium to large bunches of smallberries. Good flavor with low acidcontent. The juice is pale rose.Suitable for winemaking anddessert. Very productive with atrailing growth habit. Ripens mid-September. Cane prune.

King of the Hill Zone 4bProductive and vigorous vines.Medium-sized, dark blue berriesare juicy and tart; borne in tightclusters. Excellent for juice andjelly. Appears to be quite tolerant ofcommon grape pests. One of thebest of type in Wisconsin trials.Cane prune.

Worden Zone 5aModerately productive, small clus-ters with large berries. Fruit hassprightly, rich flavor. Good for juiceand jelly. Medium vine vigor, needsless space than other cultivars.Ripens mid- to late September.Cane prune.

Concord Zone 5aThe standard of flavor and qualityfor American blue grapes whenfruit is fully matured. Good forjuice and jelly. Very susceptible toblack rot and phomopsis cane andleaf spot. Vigorous and productivevine. Ripens early October, oftentoo late to mature before killingfrost. Cane prune.

White-, yellow-, andgreen-fruited cultivarsHimrod Zone 5bNot fully hardy, may often be win-ter-injured. Large, loose clusterswith small, nearly seedless, sweetberries. Suitable for wine and tableuse. Very productive when notwinter-injured. Ripens mid- to lateAugust. Cane prune.

Zone 3a

Zone 3b

Zone 4a

Zone 4b

Zone 5a

Zone 5b

FIGURE 1. Hardiness zones for Wisconsin.

3a

5b

5a

4a

4b

3b

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Kay Gray Zone 4bSmall fruit clusters with medium-sized, seeded berries. Fruit has dis-tinctive, pungent flavor. Suitablefor wine and table use. Vigorousvine with trailing growth habit.Ripens somewhat unevenly in lateAugust. For trial plantings only.Cane prune.

Edelweiss Zone 4bA large-clustered white Swenson-hybrid grape suitable for wine andtable use. Harvest early for best fla-vor. Vines are vigorous and moder-ately productive. Cane prune.

La Crosse Zone 4bA white Swenson-hybrid grape.Good for fruity wine. Moderateproduction and vigor. Ripens earlyto mid-September. For trial plant-ings only. Cane prune.

Esprit Zone 4bVigorous grape with mild, fruityflavor. Good for table or wine use.Ripens mid- to late September. Fortrial plantings only. Cane prune.

Red-fruited cultivarsReliance Zone 5bSeedless red grape. Medium-sizedclusters with medium to largeberries. Fruit is moderately sweetwhen fully mature, good for tableuse. Very susceptible to black rotand downy mildew. Ripens mid-September. Cane prune.

Frontenac Zone 4aFrom the University of Minnesota.Easy to manage with vigorousgrowth habit. Productive and quitedisease tolerant. Produces aromaticwine reminiscent of cherry or berry.Ripens mid- to late September.Cane prune. For trial use.

Swenson’s Red Zone 5aModerately hardy, seeded grape.Medium to large clusters with thin-skinned berries. Mild-flavored, canbe refrigerated up to 3 weeks. Forfresh use. Fruit develops colorunevenly and should be left onvine until fully mature. Susceptibleto downy mildew and phylloxera.Ripens late September. Cane prune.

FRENCH HYBRIDGRAPESToday’s numerous French hybridgrapes are products of breedingprograms designed to blend thedisease and insect resistance ofAmerican grapes with the tableand wine qualities of the Europeangrape species and are suited almostexclusively for winemaking. Ingeneral, French hybrid grapesare not hardy in Wisconsinand are not suggested forextensive planting. For the avidhobbyist willing to accept somewinter injury with reduced produc-tion, the following are suggestedfor trial plantings only.

French hybrid cultivarsAurore Zone 5aVigorous vine with long cylindricalfruit clusters. Medium-sized berriesturn golden color with pink blushwhen fully mature. Moderatelyproductive. Very susceptible toblack rot and powdery mildew.Ripens early September.Spur prune.

Foch Zone 4bThe leading red wine grape forcommercial growers. Very vigorousand productive. Black fruited,small clusters with small berries.Moderately hardy. Ripens mid-September. Cane prune.

Leon Millot Zone 4bVigorous vines with adequate har-diness, similar to Foch. Develops aBurgundy-like bouquet with properaging in the bottle. Cane prune.

Aris Zone 5aEarly ripening, white berry with ahigh sugar concentration (brix level).Excellent wine if cool fermented.Yields may be low. Cane prune.

Baco Noir Zone 5aVigorous plant, black fruited, longclusters with small berries.Moderately productive in limitedtrials. Very susceptible to black rot.Ripens mid-September. Spur prune.

Chancellor Zone 5bBlue-black, medium-sized berriesin medium to large, loose clusters.Yields similar to Concord. Makesexcellent full-bodied red wine.Susceptible to downy mildew.Ripens late September. Spur prune.

Seyval Blanc Zone 5bLarge clusters of small, whiteberries. Moderately vigorous.Produces excellent dry wine.Resistant to some diseases. Ripens

late September. Spur pruneand cluster thin.


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PLANTING STOCK ANDPROPAGATIONHome gardeners and beginning commercialgrowers should purchase planting stock fromreputable commercial nurseries or garden cen-ters. Vigorous, well-rooted dormant plants aresatisfactory. Occasionally, nurseries will have2-year-old plants or potted plants for sale. Theseare also suitable and may produce more vigorousgrowth in the first season. But carefully considerany extra costs in buying older plants, especiallyif buying large quantities.

Grape cultivars, like other perennial fruits, mustbe propagated from vines since seedlings do nothave the same characteristics as the parent plant.Layering or hardwood cuttings are the mostcommon methods. It is illegal to propagatepatented cultivars without permission.

If only a few plants are desired, layering is a sat-isfactory propagation method. In layering, selecta 1-year-old cane near the vine base. Make atrench that is 4 to 5 inches deep. Lay the cane flatin the trench and cover at least two buds withsoil. Cut off the tip, leaving two buds above thesoil. Canes usually root well and can be cut fromthe parent vine, dug and transplanted early thenext spring before growth begins.

For propagation by hardwood cuttings, select1-year-old dormant canes late in winter. The bestcanes are live, green under the bark, undamaged,and 1⁄4 to 3⁄ 8 inch in diameter. Cuttings shouldhave at least three buds spaced 4 to 6 inchesapart. Bundle and store the canes in moist (notsoggy) sawdust or sand. Keep the bundles inrefrigerated storage (34° to 40°F) until needed.Cuttings of winter-tender cultivars should be col-lected in early November and stored through thewinter in moist sand, peat, or sawdust.

Early in spring, set the cuttings 6 inches apart inwell-drained, tilled soil in the nursery row. Setcuttings upright in a trench with the two lowerbuds covered and the top bud just above the soilsurface. When planting, be sure to place the cut-ting so the buds that were nearest the trunk of

the vine are below the soil and the bud that wasfarthest away is above the soil. Press soil firmlyaround the cuttings and water to maintain ade-quate and consistent soil moisture levels. Plantsshould receive at least 1 inch of water weekly.Rooted cuttings can remain in the nursery rowuntil transplanted to the permanent locationbefore growth begins early the next spring.

An alternative to the trenching method describedabove is to lay down a sheet of black plastic. Cutholes into the plastic where you want to plant.Push cuttings through the holes and firm the soil.The plastic heats the soil and prevents weedcompetition. You’ll need a soaker hose beneaththe plastic to water the plants.

Dormant hardwood cuttings are also easilyrooted in the greenhouse if planted in deep potsor tall paper cups as described above for fieldplantings. Pots or cups must have drain holes.Greenhouse-grown plants should be acclimatedin an outdoor lath house or cold frame beforetransplanting to the field.

PLANTING DESIGN ANDROW SPACINGWhen possible, lay out the vineyard in straightrows which are easier to manage and reduce trel-lis costs. Rows longer than 500 feet pose trellisanchorage and support problems. On steeplysloping land, design rows to follow the grade orcontour to help prevent soil erosion. ContactNational Resource Conservation Service techni-cians in your county to assist in contour designfor larger vineyards. If possible, arrange rows ina north-south orientation to allow maximumexposure to the sun.

Row spacing depends in part on the training andtrellis system. In backyard plantings, 9 feetbetween rows is generally suitable. For largerplantings using conventional farm tractors, spacerows at least 10 feet apart and leave 30 feetbetween the edge of the field and the beginningof the row.

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For the umbrella kniffin or Geneva double cur-tain training systems, space plants in the row 9feet apart. If using the single cordon system,space American grapes 12 to 14 feet apart in therow. These systems are described in the sectionon training and pruning.

PLANTINGPlants can be purchased either potted or as bare-root nursery stock. Bare root will be cheaper forlarge plantings. Potted plants are convenient forhome gardens. Handle plants carefully to avoiddamage or drying out. Set out plants as early asthe soil can be worked without clumping.

Store dormant bare rootstock in moist sawdust ina cool location (32° to 40°F) until they can beplanted. If this is not possible, heel in plants bydigging a shallow trench on the north side of abuilding; place the plants in the trench and coverthe roots completely with soil. Keep plants wellwatered. During planting, place bare roots in abucket of water—but don’t hold them in waterfor more than 8 hours. Prune off all but one vig-orous cane and any broken and long roots.Spread the root mass in the hole and plant at thesame depth as in the nursery. Fill around theroots with soil. Firm the soil and then water.Water newly planted vines every few days tokeep the roots from drying.

Potted stock can be planted in the spring or sum-mer. Make sure the soil in the pot does not dryout before planting. Plants are best held in a cool,shady location. Dig a hole slightly deeper andwider than the pot. Remove the pot and examinethe root ball. If large roots are winding aroundthe root ball make vertical cuts through the rootsand spread them away from the trunk. Place theroot ball in the hole. Fill the hole with soil andfirm it around the plant, then water.

For either potted or bare root plants, insert astake near the plant and loosely tie the vine inplace. The stake will keep the trunk straight andtrain the vine upwards. Once the vine reaches thetrellis the stake can be removed. See the sectionon training and pruning for more details.

SOIL MANAGEMENT ANDWEED CONTROLVineyards planted on slopes have special soilmanagement problems. Unprotected soils onslopes will erode easily. Using equipment inmuddy soils is difficult. Maintain a permanentsod cover between the rows. Sod will hold thesoil in place, support equipment, and reduce soilcompaction. Perennial rye, red fescue, andKentucky bluegrass are all suitable sod grassesfor vineyards. The best time to establish the sodis the fall BEFORE planting. By doing so the sodwill be established and will support traffic forspring planting. Mow the sod between the rowsfour to five times per year.

Grass and other vegetation should not beallowed to grow under the trellis or around thevines. Weeds compete with the vines for waterand nutrients. Grasses are the most competitiveweeds. Weeds in the row can be controlled withherbicides, cultivation, or mulching.

Several herbicides are registered for use ongrapevines. Carefully read product labels beforeapplying any herbicide to grapes. Don’t use 2,4-Dherbicides anywhere near grapevines as it cancause flower abortion and misshapen foliage.Avoid using herbicides the first year aftergrapevines are planted.

Special cultivators called grape hoes can be usedunder the trellis to manage vegetation. Thisequipment leaves some vegetation around thetrunk that will have to be hand hoed for com-plete control.

For small plantings cultivating to a depth of 1 to2 inches with a sharp hoe or shovel will helpkeep weeds down. Or mulch can be used to con-trol weeds. Organic materials such as straw, hay,sawdust, shavings, or wood chips are acceptablefor mulching. Some weed barrier fabrics whencovered with a thin layer of mulch will also limitweed growth. Apply mulches in a doughnutfashion around the vines. Don’t mound themulch around the trunk.


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FERTILIZATIONAs noted previously, a soil test before planting isimportant to determine soil pH and nutrientneeds. Lime, phosphorus, and potassium do notmove readily through the soil. If the soil is testedthe summer or fall before planting, you can applyand till needed nutrients into the soil during thefall. This saves time in the spring by reducing theneed for preplanting soil preparation.

While grapes grow successfully over a widerange of soil pH, a soil pH of 6 to 7 is optimal forsoil nutrient availability. Where a soil test indi-cates a need for lime, apply only the suggestedamount and incorporate it into the soil. Repeatsoil tests at least every three years to monitorchanges in pH or nutrient availability.

Nitrogen is normally needed annually. All formsof nitrogen fertilizers currently available inWisconsin are satisfactory for grapes. On soilswith a pH above 7.0, ammonium sulfate or ureais preferred. Apply 20 to 25 pounds of nitrogenfertilizer per acre to vineyards in the spring afterthe soil thaws and before growth begins.

Before applying additional nitrogen in mid-June,assess damage to the vines. If vines were injuredduring winter or if the blossoms were killed byfrost, do not apply any more nitrogen fertilizer. Ifwinter injury is minimal and fruit are developing,apply 20 to 25 pounds of nitrogen per acre. Twoapplications at lower rates permit some control ofvegetative growth which is likely to be excessivefollowing winter injury or fruit crop loss.

Grapes rarely need micronutrient fertilizers inWisconsin. If you suspect a micronutrient defi-ciency, submit a sample for foliar analysis to verifya need before applying the fertilizers.

County Extension offices throughout Wisconsinhave instructions for taking and submitting soiland foliar samples to suitable laboratories.

FLOWERING AND FRUIT SETGrapes are self-fruitful so blocks of a single culti-var may be planted. Grape flowers are not showyand insects are not required for pollination.

Grapevines typically set more fruit than they canfully support. Training and pruning systems aredesigned to optimize crop load. In some cases itmay be necessary to thin the clusters to maximizefruit quality.

Cluster thinning is used to eliminate excess andsmall fruit clusters. Benefits include higher berrysugar levels, earlier ripening, and improved win-ter hardiness by preventing excess stress on thevine. If properly done, cluster-thinned vines havenearly equal yields of non-thinned vines. Clusterthinning is typically most effective on cultivarswith large berry clusters like Swenson Red,Seyval and Edelweiss, and least effective onsmall-clustered wine cultivars like Foch andMillot. Remove clusters nearest the shoot tipsand also the smallest clusters about 1 week priorto bloom. Usually only one or two clusters areretained per shoot. If a vine has 40 fruitingshoots, keep 40 to 80 clusters.

HARVESTING AND STORAGEGrapes change to their mature color long beforethey are ready to harvest. The fruit does not con-tinue to ripen after harvest, so harvesting earlywill hurt quality. The best way to check for matu-rity of grapes is to taste the berries periodically.The proper stage for harvest depends on howyou intend to use the fruit. Fruit that will be usedfresh or in juice or jelly should be left on thevines until the flavor is sweet and full. Fruit thatwill be made into wine may be harvested some-what earlier while the acid content is higher.

Once harvested, grapes can be stored for 1 to2 months at 34°F. Grape quality declines overtime in storage. The best quality products will bemade shortly after harvest. To store grapes forlater use, place them in vented plastic bags in arefrigerator. Most refrigerators can only maintain

B.

A.

3–4'

4'

45°

3'

6'52"

Trellis wires

Ground line

4–5' Screw anchor

Cross bar

Cordon wires

Concrete fill

Trunk support wire

31⁄2'

9

40°F, while the best storage temperature for fruitis 32° to 34°F. Don’t wash the fruit before storageas the water can spread diseases and it is difficultto dry berries on the cluster interior.

TRELLIS CONSTRUCTIONGrape trellis construction is similar to farm fenceconstruction, but grape growers must be espe-cially careful to allow for adequate bracing andtrellis strength since vines and fruit create severeloads which increase with strong winds.

Construct trellises during the first growing sea-son or prior to growth the following spring sothat vines can be trained early.

End posts should be larger than line posts. Usepreservative-treated posts that are 9 feet long and6 inches thick. Other suitable materials include

concrete posts or railroad ties. Set end posts atleast 3 feet deep and leaning slightly away fromthe line posts (direction of wire tension). Topwires for most trellises should be at least 6 feetabove the soil for maximum light exposure ofcanopy leaves. If you’ll be training winter tendervarieties using the J-system or spur-pruned rosesystem, trellises only need to be 4 feet tall. Figure2 shows two common bracing methods.

Use treated line posts that are 8 to 9 feet long and3 inches thick. Set the posts 24 to 36 inches deepand 20 to 24 feet apart in the row depending onvine spacing.

For the umbrella kniffin or other kniffin and thesingle cordon training systems, number 9 galva-nized wire or the newer high-tensile steel wire ispreferred for the top wire. Number 10 or number11 wire is suitable for lower wires. Avoid using

Ground line

FIGURE 2.Two common methodsfor bracing vineyardtrellis end posts.A is satisfactory forsingle cordon orumbrella kniffin trainingsystems. B is preferredfor Geneva doublecurtain training system.

6'


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large diameter plastic strand (monofilament) as itdoes not provide adequate support for conven-tional grape trellises.

The wire attachment to end posts should providea way to adjust wire tension. Since wires contractin winter and may damage the trellis, loosen thewires in fall. In spring, tighten wires after prun-ing but before tying the vines to wires.

For small home plantings, relatively inexpensive10- to 12-inch-long heavy-duty turnbuckles,available from hardware or farm supply stores,are slow but effective aids to adjust wire tension(figure 3). Owners of larger vineyards shouldbuy cinching or cranking devices which can rap-idly adjust wire tension.

To help move equipment and transport fruit atharvest, limit trellis rows to 300 feet in length.Trafficways between trellis spans should be wideenough to allow tractors or other equipment toturn into adjacent rows.

A. Turnbuckle

B. Ratchet tensioner

C. Crank tightener

FIGURE 3. Alternative methods for adjustingand maintaining grape trellis wire tension.

D ifferent types of grapes have differ-

ent fruiting habits and are, therefore,

trained and pruned differently. American

grapes typically produce fruit at the sec-

ond to the fifth cane nodes. Such vines

should be cane pruned to leave fewer,

longer canes. When cane pruning vines

you should also leave renewal spurs

among the canes. These spurs will pro-

duce fruitful growth for the following year.

European and French hybrids typically pro-

duce fruit on the second and third cane

nodes. These vines should be spur pruned

leaving a greater number of short canes

(spurs). Refer to the cultivar list (page 4)

for direction on which cultivars should be

cane or spur pruned.

Renewalspur

Leave five or morebuds on each cane.

Leave two to threebuds on each cane.

CANE VS. SPUR PRUNING

Cane pruning

Spur pruning

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TRAINING AND PRUNINGA training and pruning system should be chosenbefore the vines are planted for proper spacingand to build the trellis system. Criteria to con-sider when choosing a system are type of vinesplanted, space available, and the expertise of thegrower.

The single cordon, umbrella kniffin, and Genevadouble curtain training systems are well suitedfor Wisconsin. The J-system and spur-prunedrose system are good choices if growing grapesthat aren’t fully winter hardy for your area. Allof these systems are easy to use and allow goodlight penetration to the leaf canopy. The illustra-tions and text on the following pages show howto establish, train, and prune these systems.

Vine establishmentFirst year

After planting vines and before any growth, cutoff the remaining cane leaving two buds abovethe soil surface.

If trellis wires are in place, tie twine to a stakedriven in near each vine and stretch it verticallyto the wire directly above the vine, or drive scraplumber stakes 4 to 5 feet in length into the soilnear the vine. Tie new growth to the twine orstake. Keep the ties loose to prevent new shootsfrom being girdled by the tie.

Second year

To prevent delay and lost production, decidewhich training system to use and install theappropriate trellis before the second season.

During second-season dormant pruning, chooseone or two straight canes for the permanent vinetrunk and tie the cane tip tightly to the upper-most wire it will reach.

First year Second year Third year

V INE ESTABLISHMENT


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Third and succeeding years

While proper pruning and training might seemexcessive to the novice, growers should yearlytrim all but a fraction of the several hundredbuds on a mature healthy grape vine to leave aproper balance of fruiting wood to vine growthfor maximum production of high quality fruit.

Leaving all of the buds on the vine lets the plantoverproduce; the vine expends most of its energyin excessive vegetative growth. Unpruned grapevines produce small berries, have delayed fruitripening, and produce weak unproductive woodfor the following season.

For vigorous American grapes, 50 to 60 buds willusually produce crops of 16 to 20 pounds pervine or 5 to 6 tons of fruit per acre.

Single cordonTraining system. The single cordon system isthe simplest training and pruning system. It isparticularly well suited for European or Frenchhybrid grapes but also works for Americangrapes. Vines may be either spur or cane pruned.

Staple a single wire to the top of vertical posts formaximum strength and support. The wire shouldbe about 6 feet above the soil. Space plants 12 to14 feet apart to allow for vigorous growth.

Pruning technique. Train a single cordon tothe wire. Loosely tie young canes to the wires,extending the cordons 6 to 8 feet in oppositedirections. To reduce cordon sagging, wrapyoung canes several times around the wire andtie tightly to the cordon end.

Once cordons are established, select 10 to 12downward growing new fruiting canes close tothe trunk and prune all excess new canes and allold fruiting canes. Cut the selected canes to fourto six buds each, following the proceduresdescribed in the balanced pruning section.

Leave renewal spurs on the cordon to producecanes for the following year.

SpringThird season

WinterThird season

SpringFourth & following seasons

S INGLE CORDON

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Umbrella kniffinTraining system. The umbrella kniffin systemis well suited to American grapes. In this systemthe vines are head trained and cane pruned. Thetrellis consists of two wires, one at 51⁄ 2 to 6 feetand the second at 3 feet from the soil surface.

Pruning technique. Train the single trunk to4 to 6 inches below the top wire. Canes andrenewal spurs originate from the head and aredrooped over the top wire.

Each dormant season, cut old fruiting canes fromthe head. Retain two to six fruiting canes; fourcanes are most common. Each cane should have10 to 15 buds.

Bend the remaining canes sharply over the topwire and tie tips tightly to the lower wire. Spreadcanes to use all the space available.

Leave four to six renewal spurs (two buds each)at the vine head to produce the following sea-son’s fruiting cane. Keep fruiting wood andrenewal spurs at the head to maintain the system.

Geneva double curtainTraining system. The Geneva double curtain(GDC) system is designed for machine harvest-ing, but is suitable for hand harvesting. This sys-tem is cordon trained and may be either spur orcane pruned. Any grapes can be trained to theGDC, but it is ideal for vigorous Americangrapes. The vigorous growth is trained into offsetcanopies to allow maximum light exposure. TheGDC is a more complex system with a moreexpensive trellis and requires more expertise toimplement. Only completely winter hardy culti-vars should be trained to this system. If vines arewinter injured then significant structure must beregrown.

Attach the trellis wire to the posts, 41⁄ 2 feet abovethe soil. This wire will support the trunks. To cre-ate the trellis arms, nail a sturdy board (1 inchthick, 6 inches wide, and 4 feet long) at the top ofeach post. Attach cordon wires at each end of thetrellis arms. These wires will support the cor-dons, or arms. In a row of grape vines, trunks aretrained alternately to the left or right cordon wire.

SpringThird season

WinterThird season

SpringFourth & following seasons

UMBRELLA KNIFFIN

Pruning technique. In the Geneva double cur-tain system, retain short fruiting canes (four tosix buds each) on permanent arms or cordons.When establishing cordons after the initial plant-ing year, loosely tie young canes to the wiresextending the cordons 6 to 8 feet in oppositedirections. To reduce cordon sagging, wrapyoung canes several times around the wire andtie tightly to the cordon end.

Once cordons are established, select 10 to 12downward or outward growing new fruitingcanes close to the cordon and prune all excessnew canes and all old fruiting canes. Cut theselected canes to four to six buds each, followingthe procedures described in the balanced prun-ing section below.

Leave renewal spurs on the cordon to producecanes for the following year.

Balanced pruningIndividual grape vines vary in vigor and produc-tivity. Balanced pruning will improve yields,fruit quantity and quality, maximize each vine'sexposure to sunlight, minimize excessive growth,and maintain good vine vigor.

For most American grapes, follow the 30 plus 10system. Retain 30 fruiting buds for the firstpound of prunings plus 10 buds for each addi-tional pound. For a vine with 3 pounds of prun-ings, retain 50 fruiting buds. Do not countrenewal spur buds. For French hybrids, followthe 20 plus 10 system. Retain 20 fruiting buds forthe first pound of prunings plus 10 buds for eachadditional pounds. Retain a maximum of 40 to 50buds.

For example, in using the umbrella kniffin sys-tem remove all but five or six fruiting canes, alsoleaving six to eight renewal spurs with two budseach arising from the head. Weigh the pruningsand determine the total bud number needed. Cutoff additional fruiting canes and cut tips ofremaining canes to reach the desired bud total.After several weighings, you should be able toestimate the number of buds to leave withoutfurther weighing.

Pruning disposalFor very small vineyards or home plantings, cut,bundle and remove the prunings. For largerplantings, prunings may be chopped with a flailmower or power mulcher and left in the vine-yard for mulch.


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SpringThird season

WinterThird season

SpringFourth & following season

GENEVA DOUBLE CURTAIN

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MANAGING GRAPEVINES INCOLD CLIMATESIf planting grape cultivars that are not fullyhardy in Wisconsin or if growing hardy cultivarsin areas with severe winters, there are some cul-tural techniques that will increase your chancesfor successful grape production. These practicesare more labor intensive than the systems previ-ously described and will likely be unprofitablefor large-scale grape production. However, theydo allow a wider selection of cultivars for smallplantings.

If using straw mulch to protect vines, you mustbait for rodents. A wax brick bait containing zincphosphide works well. Place bait around theouter edge of the planting. Reduce rodent habi-tat by mowing the vineyard and surroundingareas in the fall.

Training and protectingwinter-tender vinesJ-system

This system produces angled trunks that are lesslikely to crack or break when removed from thetrellis each winter.

At planting, place the vine at a 30° to 45° angle.Pin new growth to the ground. Once the vine is24 inches long, tie it to a flexible support andtrain it onto the lowest trellis wire. During thenext 2 years the trunk becomes fully established.

The actual training and pruning system useddepends on the cultivar. The vines are headed(pruned off) at the bottom trellis wire at 12 to 18inches above the ground. This forces new canegrowth at that point. These canes will form thepermanent structure of the vine. Spread thecanes across the trellis in fan fashion.

As soon as the leaves drop in the fall, prune thevines and remove the plant from the trellis. Pinthe plant to the ground using wire hoops. Ifusing soil cover the vines with at least 3 inchesof soil in late October or early November beforethe soil freezes. If using straw, wait until the

At planting

First year

Second year

15"

36"

J-SYSTEM


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ground is frozen to a depth of 1 to 2 inches; coverplants before temperatures fall below 20°F, evenif the soil isn’t yet frozen. Mulch to a depth of3 to 4 inches. This is equivalent to about one baleof straw (30 to 45 pounds) between trellis posts.Straw should be clean and free of weed and grainseed. In the spring, uncover the vines and placethem back on the trellis by mid-April or beforebudbreak.

Spur-pruned rose

The spur-pruned rose system keeps the trunkshort, so hay or soil can be mounded around itfor easy winter protection. However, the plantgrows closer to the ground, making harvest lessconvenient. This system works well with spur-pruned cultivars like Aurore, Chancellor, andSeyval Blanc. Use two or three trellis wiresplaced 15 and 36 inches above the ground to sup-port the vines. The number of wires neededdepends on the vigor of the vine. As young canesgrow in the spring, spread them out in a fanshape to maximize light exposure. In early win-ter, prune back multiple short canes or spurs.Mound straw around each trunk before tempera-tures fall below 20°F. Remove the straw in earlyspring before budbreak or by mid-April.

INSECT PESTSAlthough widespread major insect problems ongrapes are relatively rare in Wisconsin, localizedpest problems require prompt and thoroughattention. The key to controlling grape insectpests is to frequently examine plants for signs ofpest activity and apply controls before the vine,leaves, or fruit are seriously injured. Grape grow-ers should learn to recognize the most commoninsect problems in this state. For more informa-tion on controlling pests or diseases, checkExtension publication Grape Pest Management forHome Gardeners (A2129).

Grape berry mothGrape berry moth is probably the most importantgrape pest in Wisconsin. The damaging stage is agreenish to purple larva (worm) which is about3⁄8 inch when full-grown. The insect overwinterson the ground in a cocoon formed the previousyear. In late May to early June, the mottledbrown adult moth, 1⁄4 to 3⁄8 inch in length, layseggs on the clusters of flowers or small fruit.Usually the larvae spin noticeable webbing onthe flower or fruit cluster where they are feeding.In July the fully grown larva forms a small leafflap which it then folds around its body. Thesecocoons may remain on the leaves or may fall to

Wintermulch

Third year Subsequent years

15"

36"

S PUR-PRUNED ROSE

the ground. The one to two additional genera-tions in the summer feed by tunneling throughthe fruit. Each larva can feed on three or moreberries, causing them to shrivel or drop. The lastgeneration larvae fall to the ground and formoverwintering cocoons from leaf debris underthe vines.

Where grape berry moth has been a problem,examine flower clusters for webbing and smalllarvae starting about 5 days before first bloom. Iflarvae are found, apply an approved insecticide.Immediately after bloom, inspect fruit clustersfor webbing, damaged berries and larvae. Beginweekly inspections for summer generation injuryin early August. Commercially availablepheromone traps can be used as an aid for moni-toring adult flight and egg-laying periods.

Grape leafhoppersSeveral species of leafhoppers attackgrape foliage. Adults are wedge-shaped, active insects, about 1⁄ 8 inchlong, usually whitish to pale yellowwith yellow or orange markings. Bothadult and immature stages feed by sucking juicesfrom the leaves. They usually feed from thelower leaf surface, primarily on younger foliage.Leaves first turn speckled white, then take on apale, blotchy appearance. If infestations are largeenough, the leaves will turn brown and fall fromthe vines. Leaf injury will reduce vine growthand may interfere with berry ripening. To moni-tor for leafhoppers, examine the undersides ofleaves for the small, active insects and theirwhite cast skins.

Adult leafhoppers overwinter under leaves onthe vineyard floor or in adjacent protected loca-tions such as brush piles or fence rows. They

return to the vines in spring to feed and lay eggs.The population is continuous through the grow-ing season, with probably two generations peryear in Wisconsin.

Control leafhoppers if populations are largeenough to discolor leaves. The first applicationmay be as early as post-bloom. Otherwise, con-trol as needed during the summer months.

Grape flea beetleBoth adult and larval stages of grape flea beetleinjure plantings. The adult beetle is about 1⁄4 inchlong, somewhat oval, and a dark metallic blue-black color. It overwinters in the leaf litter belowthe vines or in adjacent protected locations suchas brush piles and fence rows. It flies to vines onwarm sunny days in early spring at about thetime primary buds are beginning to develop. Ittunnels into these developing buds, preventingcane development. By the time the buds areabout 1⁄ 2 inch long with some leaf development,the beetles start feeding on the developingleaves, resulting in distorted leaves with holes.During this time the adults are laying eggs onvines. The eggs hatch into caterpillar-like larvaewhich feed on the upper leaf surface producingdead brown spots and holes. When about 1⁄4 inchlong, the full-grown larvae drop from the leavesand pupate in the soil. There may be a partialsecond generation in Wisconsin.

Monitor for adults on warm spring days aroundbudbreak. If you see the beetles, apply approvedchemicals. Larvae are usually controlled bysprays aimed at grape berry moth; otherwisecontrol as needed.

CutwormsCutworms occasionally cause serious damageearly in the season by cutting off the new devel-oping canes. Damage is usually more common inweedy areas, and weed control reduces the likeli-hood of cutworm injury. If cutworms are a prob-lem, use an approved cutworm bait.

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Grape berry moth adult, larva, and cocoons


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Grape phylloxera

Grape phylloxera is a tiny aphid-like insect thatcauses small round growths on the foliage. Thesegrowths, called galls, are not injurious when theyare few in number. To control, apply an approvedspray at the first sign of gall formation. Grapephylloxera also attacks the roots of some grapes,causing root galls. European varieties on theirown rootstock are most susceptible to attack.Most grapevines sold today are grafted ontoresistant native rootstock which is not damagedby phylloxera.

Japanese beetleJapanese beetle is a relatively recent invader ofWisconsin. The 1⁄ 3 inch beetles are reddish brownand metallic green, with a series of white tufts ofhair around the edge of the wing covers. Theyfeed on many types of trees and shrubs, includ-ing grape plants, from late June to early August.Populations can build to very large numbers,resulting in substantial defoliation. The beetlesare strong fliers and can invade from consider-able distances. Modest defoliation will not affectmature grape plants or yield, but defoliation over10%, especially after the young grapes begin toform, can decrease yield. Substantial defoliationto young plants will delay their establishment.Beetles usually do not feed directly on the fruit.

Many insecticides registered for use in grape pro-duction will kill Japanese beetle adults, but oth-ers may soon fly in. Traps can catch thousands ofbeetles, but, because they can attract more beetlesthan they catch, research has shown that their usecan actually increase damage to small gardens. Ifusing traps, place them at least 50 feet away fromplants you wish to protect. If you have a smallplanting, you may find success using the wovenfabric “floating row covers” that are available toprotect garden plants from flying insects.

Rose chaferThe rose chafer adult is a light brownbeetle about 5⁄8 inch in length withlong slender legs. This is the dam-aging stage. The beetles fly into thevineyard from surrounding grassyareas and feed on foliage, blossoms anddeveloping fruit. They are a more seriousproblem in areas of sandy soil, where the grub-like larvae feed on the roots of grasses.

Although readily killed with approved insecti-cides, rose chafers can do considerable damage inareas where they are abundant, by continuousimmigration into the vineyard. The flight periodusually persists for only 1 to 2 weeks, but two tothree insecticide applications may be neededduring this time. Home growers with smallplantings can cover the vines with cheese cloth orfloating row covers during this period. Coverageshould be completely to the ground. For moreinformation on rose chafer, consult Extensionpublication Deciduous Tree and Shrub Disorder:Skeletonizing by Rose Chafer (A3122).

Spider mitesSpider mites occasionally can dam-age foliage during prolonged peri-ods of warm, dry weather. Spidermites are extremely small, measur-ing about 1⁄ 32 of an inch. Color varies from paleyellow to red. They feed on the undersides ofleaves in a fine network of webbing. Feeding cancause the leaves to yellow and wither, reducingvine vigor and interfering with berry ripening.Treat with an approved miticide when needed.

DISEASESOnly a few diseases cause significant economicdamage to grapes grown in Wisconsin. Most ofthese are caused by fungi, although some arecaused by bacteria and viruses. Black rot anddowny mildew usually cause the most damage.If not managed, diseases can reduce yields andaffect the quality of juice and wine.

Size of aperiod.

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Effective, consistent disease management isessential for long-term productivity. The bestapproach integrates planting resistant cultivars,following cultural practices that discourage dis-ease development, and applying chemicals onlywhen necessary to avoid serious damage.Effective disease management begins with accu-rate diagnosis. For assistance identifying a dis-ease or to confirm your diagnosis, contact yourcounty Extension office.

Resistant cultivars. Grape cultivars vary inrelative resistance to the different diseases.Unfortunately, many of the most desirable culti-vars are susceptible to one or more importantdiseases. Select cultivars adapted to your region,choosing varieties that are least susceptible todiseases known to be a problem in your area.

Cultural practices. The following culturalpractices help limit disease development.

■ Plant only certified, virus-free vines obtainedfrom a reliable nursery. Diseases caused byviruses cannot be controlled once established,so they must be kept out from the beginning.

■ Select a site, orient rows, and prune vines tomaximize air circulation and promote dryingin the canopy since infection by fungi and bac-teria often requires plant surfaces to be wet forprolonged periods.

■ Eliminate diseased plants or plant parts,which may be a source of contamination forthe remaining healthy plants.

■ Destroy wild or abandoned grapevines nearvineyards as these may be reservoirs forpathogens (particularly viruses).

■ Do not fertilize excessively with nitrogen. Thisproduces dense growth that dries slowly.

Chemical control. The use of fungicides tocontrol certain diseases—especially black rot anddowny mildew—will be necessary in most yearsto maintain a quality vineyard and consistentfruit production. However, registration and avail-ability of fungicides can change unexpectedly.

For information on currently registered chemi-cals, consult Extension publication Grape PestManagement for Home Gardeners (A2129), or con-tact your county Extension office.

Black rotBlack rot is one of the most economically impor-tant diseases affecting grapes grown in theMidwest and in the eastern part of the country.Both the grapevines and the fungus that causesthis disease are native to North America; there-fore, the disease usually is present wherevergrapes are grown. In wet weather, black rot cancause devastating losses if not controlled.

Symptoms. All succulent new growth, includ-ing leaves, shoots, tendrils, and berries, is suscep-tible to infection. However, leaves that have beenexpanded for more than 1 week and ripe fruit arenot susceptible. Symptoms first appear on leavesand stems. Lesions become evident on leavesabout 1 to 2 weeks after infection, appearing astan, circular- to irregular-shaped spots. Thesespots are often surrounded by narrow, dark-col-ored borders. Tiny, black fruiting bodies of thefungus (called pycnidia) usually are visible justinside the margins of lesions. Lesions can girdleleaf petioles, killing leaves. Lesions on stems andtendrils appear as elliptical, sunken, blackcankers, which can be up to 1 inch long. Onberries, lesions first appear as small, white spotswith red-brown margins. Berries then turnbrown. They eventually shrivel, turn black, andbecome spotted with pycnidia. These shriveledberries are known as mummies.

Disease cycle. The fungus overwinters inlesions on stems and tendrils or in mummies thatremain attached to the vines or fall to the ground.Infection first occurs in the spring just after bud-break. Rain or dew triggers perithecia (anothertype of fruiting body) to eject spores. The sporesland on succulent green tissues and cause infec-tion when water is present on plant surfaces forprolonged periods. Six to nine hours of leaf wet-ting is required for infection when temperaturesare 60° to 85°F. At higher or lower temperatures,longer wetting periods are required. Pycnidia


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develop in infected tissues and produce addi-tional spores throughout the season. These sporesare spread by splashing rain and cause newinfections.

Disease management. American grape culti-vars tend to be more resistant than French hybridcultivars, although they both vary considerablyin susceptibility. Highly susceptible cultivarsinclude Aurore, Baco Noir, Canadice, Catawba,Concord, Niagara, and Reliance. Foch, Fredonia,Himrod, and Maréchal Foch are moderately sus-ceptible while Delaware and Vignoles are lesssusceptible. Follow the cultural practicesdescribed earlier to help limit disease develop-ment. To prevent new infections, remove mum-mies in the fall or before budbreak in the spring.It is especially important to remove mummiesthat are left hanging on the vines; these canrelease spores throughout the growing season. Inaddition, timely applications of fungicides arenecessary in most years to avoid serious damage.

Downy mildewDowny mildew, like black rot, is native to NorthAmerica and occurs in most regions of theMidwest. It thrives in warm (55° to 85°F), wetweather and can cause serious crop loss. Also,the disease can cause early defoliation whichdelays ripening and increases susceptibility towinter injury. The disease tends to be moresevere and difficult to manage in southern thanin northern Wisconsin, with the greatest damageoccurring in August and September.

Symptoms. On leaves, lesions appear aschlorotic, yellowish areas on the upper surfacewith corresponding areas on the lower surfacecovered with white, downy growth of the fun-gus. Lesions on the upper surface may turnbrown and coalesce. If older leaves are attackedlater in the summer, look for a mosaic pattern ofsmall, yellow and red-brown angular lesions.Infected shoots, tendrils, and leaf or fruit clusterstems become distorted, swollen, or curled andoften are covered with masses of white spores.Eventually, these parts of the plant turn brown,

wither, and die. Young berries are very suscepti-ble. Infected berries discolor, shrivel, and fall offeasily. During periods of high humidity, whitespores may cover berries. The fruit becomes lesssusceptible with age; however, infection canmove into the berries from diseased stems.Infected older berries usually are conspicuous(remaining firm and turning dull green to red-purple) but may drop from the cluster.

Disease cycle. The fungus overwinters ininfected leaves that have fallen to the ground. Inthe spring, rain splashes spores from infectedleaves to new growth. The fungus can attack allgreen, actively growing parts of the plant thathave functional stomata (pores for air and gasexchange), particularly leaves. Additional sporesare produced on newly infected tissues and arespread by both wind and rain. At temperaturesabove 75°F, infection occurs when plant surfacesare wet for as little as 2 hours. When the temper-ature drops below 45°F, the fungus requires9 hours of wetness. Symptoms usually appear1 to 2 weeks after infection.

Disease management. American grape culti-vars tend to be more resistant than French hybridcultivars. Catawba, Fredonia, Niagara, andReliance are most susceptible. Aurore, Baco Noir,Canadice, Concord, Foch, Himrod, and MaréchalFoch are less susceptible. Follow recommendedcultural practices listed earlier to help limit dis-ease development. In the spring before budbreak,either bury infected leaves by cultivating aroundthe vines or remove them altogether. In addition,timely applications of fungicides are sometimesnecessary to avoid crop loss, particularly on sus-ceptible cultivars and when wet weather persists.

Phomopsis cane and leaf spotThis disease previously was called “dead arm,” aproblem that now is known to be two separatediseases—Phomopsis cane and leaf spot andEutypa dieback. Phomopsis cane and leaf spot,which is caused by a fungus, is most likely tooccur when wet weather persists after budbreak.It occurs only sporadically in Wisconsin and

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more frequently in the southern part of the state.The disease weakens vines and makes them moresusceptible to winter injury. Only under severedisease pressure are fruit infected.

Symptoms. Only young, green tissues areinfected; shoots longer than 8 inches are not sus-ceptible. Consequently, the disease is particularlya problem when cool, wet periods follow imme-diately after budbreak. Symptoms usually appear3 to 4 weeks after infection. Sunken, black, ellipti-cal lesions on shoots (including tendrils) are themost obvious symptom and occur most fre-quently on lower portions of green stems. Theselesions may coalesce to form a dark encrustedregion; severely infected stems may split length-wise. Infections on stems of leaves and fruit clus-ters are similar to those on shoots and can resultin girdling, which may cause leaf drop and shriv-eling of berries. Lesions on leaves initially appearsmall, light green, and irregular in shape, laterturning black with yellow margins. Leaves withmany lesions may turn yellow, be misshapen,and drop from the plant. Lesions may be concen-trated along veins, giving leaves a black andpuckered appearance. Usually only lower leavesare affected. The fungus also can attack the berriesand cause a fruit rot, but this is not common inWisconsin. Infected berries are light brown, eas-ily drop from the cluster, and eventually shriveland dry into mummies. These mummies can beconfused with those caused by black rot.

Disease cycle. The fungus overwinters inlesions on 1- to 3-year-old wood where tiny,black fruiting bodies of the fungus (called pycni-dia) eventually develop. In the spring, spores arereleased and dispersed during periods of rain.The fungus is inactive during the warm, drymonths of summer, but may become active againin the fall as cool, wet weather returns.Alternatively, the fungus may remain activethroughout the summer if moderate tempera-tures and rainy conditions persist. The diseasebecomes increasingly more severe if cool, wetsprings occur in successive years. The fungususually is not moved readily from vine to vine sothe disease tends to be localized in the vineyard.

However, the fungus can be moved over longdistances to new locations on infected cuttingsused for propagation or on contaminatednursery stock.

Disease management. Catawba, Concord,Delaware, and Niagara are very susceptible;Fredonia and Reliance are less susceptible; andAurore and Baco Noir are only slightly suscepti-ble. The relative susceptibility of many grape cul-tivars is not known. Follow the recommendedcultural practices described earlier to help limitdisease development. Be sure to use onlypathogen-free stock for grafting or planting andto remove and destroy diseased shoots whenpruning. In addition, one to two well-timed fun-gicide applications usually will prevent newinfections. Make the first application when newshoots are 1 to 3 inches long and, if wet weatherpersists, make another application when they are5 to 6 inches long.

Powdery mildewIn Wisconsin, powdery mildew is much lessimportant than either black rot or downy mildewand usually causes little or no economic damage.However, on susceptible cultivars and in warm(65° to 80°F), humid weather, it can reduce vinegrowth, yield, fruit quality, and winter hardiness.The disease is caused by a fungus that onlyattacks members of the grape family. Many otherplants also are affected by powdery mildew, buteach plant or group of closely related plants usu-ally is attacked by a unique powdery mildewfungus. Consequently, powdery mildew on oneplant usually does not affect other unrelatedplants. However, powdery mildew on differentplants develops under similar weather conditions.

Symptoms. All green tissues are susceptible toinfection. The fungus grows on the surface ofinfected plant parts and produces an abundanceof spores, giving them a dusty or powderyappearance. Lesions on leaves begin as small,white patches; over time, these can coalesce andcover the entire surface. Powdery mildew affectsthe upper leaf surface more severely than the


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lower leaf surface. If young, expanding leaves areinfected, they become white and powdery withfungus growth, distorted, and stunted. Infectedgreen shoots typically have lesions that look likedark brown or sooty black patches. Berries alsoare susceptible. Infection of young berries causesreduced size, failure to color, and splitting thatleads to secondary rotting. Berries of red or pur-ple cultivars that are infected as they begin toripen develop a blotchy or rusty appearance ontheir surfaces and produce off-flavored wines.Later in the season, small, brown to black, spheri-cal fruiting bodies of the fungus (called cleis-tothecia) develop on infected plant surfaces.

Disease cycle. The fungus overwinters prima-rily as cleistothecia on bark or dead leaves. In thespring, wind carries spores to new green tissues.Occasionally, the fungus may overwinter ininfected buds, in which case, new shoots becomediseased as they grow. New spores form soonafter infection and continue forming throughoutthe season. Spores are dispersed readily by wind,so once the disease has begun, it can spread rap-idly through the vineyard. Unlike black rot anddowny mildew, plant surfaces do not need to bewet for infection. In fact, rainfall tends to inhibitspore germination and disease development.

Disease management. American grape culti-vars tend to be more resistant than French hybridcultivars. Aurore is highly susceptible; Baco Noir,Concord, Foch, Fredonia, and Himrod are moder-ately susceptible. The cultural practices describedearlier—particularly those that improve air circu-lation to promote drying in the canopy—mayhelp reduce disease severity. If the disease everbecomes a serious problem, applications of sulfuror other effective fungicides should provide con-trol. However, certain cultivars, such as Concord,Foch, and Maréchal Foch are sensitive to sulfurinjury, especially at temperatures of 85°F or higher.

Crown gallCrown gall, which is caused by a bacterium,affects hundreds of different plants, includinggrapevines. It is particularly a problem onEuropean and French hybrid grape cultivars thatare grown in colder climates where freezinginjury is likely to occur and in nurseries wheregrapevines are propagated.

Symptoms. Galls typically are associated withwounds. They first appear in early summer ascoarse, white, fleshy overgrowths that erupt frombeneath the bark. Later they become brown, dry,and woody. Galls form most often on the lowertrunk just above the soil surface, but they canalso appear below ground or farther up thetrunk. Frequently, galls occur at graft or budunions. Large galls can girdle the entire vine.Diseased plants usually grow poorly, havereduced yields, and may even die.

Disease cycle. Crown gall in home plantingsmost likely occurs through the use of contami-nated planting material. The bacteria may spreadthroughout the infected plant even though theplant appears symptomless. The bacteria also cansurvive in soil for several years after being intro-duced on infected plants. Infection occursthrough wounds, such as those caused by freez-ing injury, pruning, or budding and grafting. Thepathogen is transmitted easily from plant to planton contaminated pruning or propagation tools.

Disease management. American grape culti-vars tend to be more resistant than French hybridcultivars; however, some American grape culti-vars, like Niagara, are susceptible. Sanitation andcultural practices are the primary means of dis-ease management. The use of only pathogen-freeplanting and/or propagation stock is essential.Inspect all plant material before purchasing orplanting, and reject plants that have galls or over-growths. If propagating your own plants, disin-

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fect working areas and equipment regularly. Buryor mound soil around trunks in the fall to mini-mize freezing injury. When removing infectedplants, include as much of the root system aspossible. Chemical controls are not effective orrecommended.

PROBLEM SOLVING

Why grapevines fail to bearThere are many reasons why grapevines fail tobear fruit: spring frosts, winter cold injury, age ofvines, too little pruning, or incorrect pruning.This section describes the most common prob-lems and how to avoid them (where possible).

Cold injury. Perhaps the most common problemfor grapes is cold midwinter temperatures. Fruitbuds of American grapes are hardy to about 0°Fin early December. A plant’s hardiness dependson the weather before a freeze and the durationof the cold. A midwinter warm spell (such as aFebruary thaw) can predispose the vines to injuryif a severe freeze follows. Both flower bud andvine injury or death can result from cold winters.French hybrids are less hardy than Americangrapes and are more likely to suffer winter injury.European grapes are not hardy in Wisconsin.

Once the buds begin to grow they are hardy toabout 28°F. If the primary bud is killed, the sec-ondary bud will still grow and produce a smallcrop. If the secondary bud is killed, smaller budswill produce vegetative growth but no fruit.

Vine age Grapevines generally won’t produceany grapes for 3 to 4 years after planting. Theplant has to accumulate food resources and thewood has to mature before there is sufficient vinestrength to grow fruit. Plants may take severaladditional years to produce fruit if they have notbeen pruned and cared for properly. Vines grow-ing in weedy areas may also take longer to pro-duce due to competition for water and nutrients.

Incorrect pruning. The style of pruning is alsoimportant. American grapes typically producefruit at the second to the fifth nodes along a cane.If these grapes are spur pruned to leave only twoto three buds per cane, little or no fruit will beproduced. French hybrid grapes usually producefruit at the second and third nodes of a cane. Ifthese grapes are cane pruned to leave five ormore buds per cane, they will produce much veg-etative growth at the expense of fruit production.

Gender. Some wild grapes have separate maleand female plants. Flowers on male plants pro-duce only pollen. Since the male flower has noovary, no fruit will be produced. Male and femaleplants look identical except for the difference inflowers. Gender can only be determined byexamining the flowers. Grapevines purchased atnurseries should have both male and femaleflower parts in each flower.

Exposure to herbicides. Grapevines areextremely sensitive to phenoxy herbicides such as2,4-D and dicamba. Early-season exposure tothese herbicides may cause leaf deformity andfruit drop. Late-season exposure is less likely tocause injury. These herbicides are volatile andmay travel up to 2 miles from the site of applica-tion under the right conditions. If you plantgrapevines in rural areas where cash grains orpasture land is common you can expect someinjury from phenoxy herbicides.

Poor fruit qualityIn some instances grapevines produce fruit clus-ters that are small or of poor quality. This sectiondescribes problems than can lead to poor fruitquality.

Insufficient pruning. Many gardeners leavetoo many canes (and therefore too many buds) ongrapevines. Too much vegetative growth limitsthe resources available for fruit growth. Thesevines produce few bunches of small grapes. Withtoo much cane growth the lower and inner partsof the vine are shaded. To correct this problem,follow the pruning advice described in the sec-tion on training and pruning.


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Neglected vines. Unpruned plants, plants thathaven’t been trained on a fence or trellis, and dis-eased or insect-infested plants typically producepoor quality fruit. Heavy pruning and pest man-agement can usually reclaim grapevines.

Poor growing conditions. When grapes areplanted in shady spots or on soils that are wetand poorly drained the vines won’t thrive. Lackof sunlight will cause long spindly growth. Vinesplanted in wet heavy soils usually die within ayear or two.

Inferior cultivars. Inferior cultivars will pro-duce inferior fruit. Chance seedlings and vinescollected from the wild are also likely to producepoor fruit. Good management cannot compensatefor poor genetics. For the best chance of success,choose cultivars suggested in this publication.

Why plantings failPlant death is usually caused by a number ofinteracting factors rather than by a single identifi-able cause. One injury may provide sufficientstress to allow other problems to kill the vine.Several common reasons for vine death aredescribed below.

Winter injury. Most American grapevines arehardy in Wisconsin on favorable sites. Duringsevere winters even these vines may be injured.European grapes and French hybrids are lesshardy. European grapevines will not survive evenmoderate winters. French hybrids will surviveand produce fruit on good sites in southern andeastern Wisconsin. Selecting appropriate cultivarsand sites will aid winter survival. Temperaturesof –10°F would likely lead to both bud and trunkinjury of French hybrids and some primary budinjury to American grapes. Temperatures of –20°Fwould kill buds and cause significant trunk andcane injury on French hybrid vines. Americangrapes would suffer less damage, but therewould be significant crop reduction. See the sec-tion on managing grapes in cold climates for tipson minimizing winter injury.

Too much water. Grapevines will not tolerate“wet feet.” Poor soil drainage is common inheavy clay soils and in low spots. Standing waterlasting more than a day in summer will likelylead to injury. When soils are flooded, water fillsthe pores in the soil that would otherwise befilled with air and can provide oxygen to theroots. Root rots are also favored on wet soils.

Too little water. Young grapevines are particu-larly susceptible to drought. When water is lim-ited, roots cannot provide the water necessary toreplace that lost through the leaves. Sandy soilsare particularly drought prone. If plants wilt inthe afternoon, they need water. Avoid droughtstress by watering vines often. Young vinesshould receive 3 to 5 gallons of water per week.Older, established vines will also benefit fromirrigation during dry periods. Grasses growingnear the vines will take up most of the availablewater. Don’t allow grass to compete withgrapevines.

Physical damage. Vines can be killed whenthe trunks are seriously injured. String trimmers,lawn mowers, and animals can cause physicalinjury. If string trimmers and lawn mowers areused too close to trunks, they can damage thelayer beneath the bark that carries nutrients tothe roots. Avoid damage from lawn equipmentby not allowing grass or other vegetation to growwithin 2 feet of the vine. This area can bemulched, cultivated, or treated with herbicides.Rodents and rabbits will gnaw on the bark forfood in the winter. If they strip off too much bark,the roots won’t get the nutrients they need andthe vine will die. Eliminate rodent habitat byremoving vegetation from around vines, includ-ing any tufts growing up against the trunk, andby keeping adjacent areas mowed (especially inthe fall). This will reduce rodent populations andthe likelihood of injury.

G LOSSARY

25

ArmA short branch extending fromthe trunk or cordon on whichcanes or spurs are borne.

CaneA one-year-old shoot.

Cane pruneA pruning technique wherecanes with 8–15 buds are left toproduce shoots and fruit thefollowing year.

CordonA horizontal extension of thegrapevine trunk. It is usuallytrained along the trellis wire. Acordon is a permanent part ofthe vine.

Cordon trainA training system where cor-dons are maintained on thevine. The Geneva double cur-tain is an example.

CultivarA contraction of “cultivatedvariety.” Describes plants thatare distinguishable by distinctcharacteristics.

Fruiting woodOne-year-old canes that willproduce the current season’scrop.

HeadThe top of the vine where canesand renewal spurs arise.

Head trainA training system where canesand renewal spurs arise directlyfrom the top of the trunk. Nocordons are retained.

NodeThe thickened portion of ashoot or cane where leaves ariseand where the compound budis located.

Renewal spurA cane pruned to one to threebuds. The spur will produce acane that will fruit the follow-ing year. These generally arisefrom the cordon or head.

SpurA cane pruned to one to threebuds. A fruiting spur producesshoots with fruit.

Spur pruneA pruning method where canesare pruned to one to three buds.This technique is generally usedwith European-type grapes.

TrunkThe main upright stem ofgrapevines from which cordons,canes, spurs, and shoots mayarise. The trunk usually lasts formany years.

Copyright © 2006 by the Board of Regents of the University of Wisconsin System doing business asthe division of Cooperative Extension of the University of Wisconsin-Extension. Send inquiries aboutcopyright permission to: Manager, Cooperative Extension Publishing, 432 N. Lake St., Rm. 103,Madison, WI 53706.

Authors: Teryl Roper is professor of horticulture, Dan Mahr is professor of entomology, andPatty McManus is professor of plant pathology, College of Agricultural and Life Sciences, University ofWisconsin-Madison and University of Wisconsin-Extension, Cooperative Extension. Brian Smith is pro-fessor of horticulture, College of Agriculture, University of Wisconsin-River Falls and University ofWisconsin-Extension, Cooperative Extension. Produced by Cooperative Extension Publishing. Pruningillustrations and graphic design by Jody Myer. Cover illustration by Catherine Baer, copyright 1998.Japanese beetle illustration by David Shetlar.

University of Wisconsin-Extension, Cooperative Extension, in cooperation with the U.S.Department of Agriculture and Wisconsin counties, publishes this information to further the purpose ofthe May 8 and June 30, 1914 Acts of Congress; and provides equal opportunities and affirmative actionin employment and programming. If you need this material in an alternative format, contact the Office ofEqual Opportunity and Diversity Programs or call Cooperative Extension Publishing at (608) 262-2655.

This publication is available from your Wisconsin county Extension office or from CooperativeExtension Publishing. To order, call toll-free 877-WIS-PUBS (947-7827) or visit learningstore.uwex.edu.

A1656 GROWING GRAPES IN WISCONSIN SR-12-2006-(R12/98)-2M

RELATED PUBLICATIONSGrape Pest Management for Home Gardeners(A2129)

Fertilizing Small Fruits in the Home Garden(A2307)

Home Fruit Cultivars for Northern Wisconsin(A2488)

Home Fruit Cultivars for Southern Wisconsin(A2582)

Midwest Small Fruit Pest ManagementHandbook (Bulletin 861, Ohio State University)

NURSERIESThis list of nurseries is provided as a conveniencefor our readers. It is not an endorsement byExtension nor is it exhaustive. These plant mate-rials may be available from other equally suitablenurseries.

J.W. Jung Seed335 South High StreetRandolph, WI 53957(800) 247-5864www.jungseed.com

Lon J. RomboughP.O. Box 365Aurora, OR 97002(503) 678-1410www.bunchgrapes.com

McKay NurseryP.O. Box 185750 South Monroe St.Waterloo, WI 53594(800) 236-4242www.mckaynursery.com

Miller Nurseries5060 West Lake RoadCanandaigua, NY 14424(800) 836-9630www.millernurseries.com

St. LawrenceNurseries325 State Highway 345Potsdam, NY 13676(315) 265-6739www.sln.potsdam.ny.us

growing grapes in wisconsin (a1656) - cooperative extension...the well-known concord grape, for...

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