for Arborists, Landscape Managers & Nursery Managers

Commercial Horticulture May 27, 2011Coordinator Weekly IPM report: Stanton Gill, Extension Specialist, IPM for Nursery, Greenhouse and Managed Landscapes, sgill@umd.edu. 301-596-9413 (office) or 410-868-9400 (cell)

Regular Contributors: Pest and Beneficial Insect Information: Stanton Gill and Paula Shrewsbury (Extension Specialists) and Brian Clark (Extension Educator, Prince George’s County)Disease Information: Karen Rane (Plant Pathologist) and David Clement (Extension Specialist)Weed of the Week: Chuck Schuster (Extension Educator, Montgomery County)Cultural Information: Ginny Rosenkranz (Extension Educator, Wicomico/Worcester/Somerset Counties)Fertility Management: Andrew Ristvey (Regional Specialist, Wye Research & Education Center)Design, Layout and Editing: Suzanne Klick (Technician, CMREC)

In This Issue...

If you work for a commercial horticultural business in the area, you can report insect, disease, weed or cultural

plant problems found in the landscape or nursery to

sklick@umd.edu

TPM/IPM Weekly Report

- Weather notes- Powdery mildew- Cucumber beetle- Exobasidium leaf gall- Brown marmorated stink bugs- Japanese maple scale- Euonymus scale- Gloomy scale- Pulvinara scale- Lecanium scale- Bagworms- Spittlebugs- White pine adelgid- Honeylocust plant bug- Fire blight- Locust leafminer- Potato leafhopper- Lesser peachtree borer- Grape growing- Entomosporium leaf spot- Emerald ash borer traps- Sawflies on roses- Beneficial insect activity

Beneficial of the WeekWeed of the WeekPlant of the WeekPhenologyDegree daysConferences

Integrated Pest Management for

Commercial Horticulture

www.ipmnet.umd.edu

If you thought we were having too much rainIt has finally warmed up and with the good weather, people are buying plants at garden centers. Most nursery and landscape managers have said – enough with the rain periods, let’s have some dry weather. Careful what you wish for - Texas is experiencing bone dry weather with the driest period in over 100 years. In Kansas it is so dry that it is damaging wheat production which will raise the price of bread. This weekend, I (Stanton) spoke with my wife’s relatives in Iowa and they said that the Midwest has been on the other extreme with one of the wettest springs in a long time. Many of the fields did not get planted in corn. This has been the wettest spring in 115 years. Seems like we are setting a lot of weather records this spring.

Powdery MildewMarie Rojas, IPM Scout, is reporting that powdery mildew is just starting to show up on ‘Cherokee Brave’ dogwoods in Beallsville. It is also being found on monarda in Ellicott City. Sunny, warm days and cool nights provide favorable conditions for this disease.

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Cucumber BeetleOliver Storm reported activity of cucumber beetle adults, Diabrotica spp. (spotted and striped), in Anne Arundel County this week. These bugs have yellowish-green colored bodies with black spots or stripes, a black head and are 1/4 inch in length. Eggs are oval in shape, yellowish-orange and laid in the soil next to host plants. The larvae are 1/4 to 1/2 inch long, with a beige to white body, brown head, brown spot on the tail end. Larvae attack plant roots and stems generally in spring for 2 to 6 weeks. The larvae and adults attack asparagus, broad beans, eggplants, potatoes, certain fruit trees, tomatoes, peas, squash, corn (a favorite), cucumbers, potatoes, fruits, and melons. This is not the limit as they will attack over 270 plants in 29 families including flowers and ornamentals. In spring, the adults will feed en masse on seedling shoots and leaves. You will see adults feeding mostly on flower parts and pollen during summer. In the fall, they turn to the upper portions of plants and will also feed on weeds and trees. They infect some stone fruits with brown rot. The striped cucumber beetle adults do the most damage to the cucurbit family.Control: Several materials are labeled for cucumber beetle control. Neem products can be used to control the larval stage of this insect.

Exobasium galls on azalea

Spotted cucumber beetle on zinnia

Row covers are being evaluated as a way to keep stink bugs off of home vegetable plants. A tight seal all of the way around the plants is very impor-tant.

Brown Marmorated Stink Bugs (BMSB)Activity of BMSB went to hyper level this week with adults buzzing around people’s houses and hanging out at lights. We are finding them on plant material in landscapes. Steve Black reported finding them flying around Amelanchier trees this week, but did not observe any feeding so far. We continue to find them feeding on peach fruit this week in the Brookeville area. At the Home and Garden Information Center (HGIC), Jon Traunfeld, is trying out floating row covers to protect vegetables in home gardens.

Exobasidium Leaf Gall on AzaleaDamian Varga, Scientific Plant Services, found Exobasidium leaf gall on azalea this week in Ellicott City and Baltimore. The symptoms start as swollen tissue on newly expanding leaves, shoots, buds or flowers. A white surface growth that contains the reproductive spores develops on these galls. The galls range in color from green to pink to red depending on the part of the plant infected. Eventually these galls turn brown and harden. They are not a serious problem on azaleas. Fungicides are not effective. It is best to hand pick galls before the white growth develops to reduce the incidence of this disease next season.

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Japanese Maple Scale Crawler Update – Get Ready!As mentioned in earlier Pest Alerts this season, and noted from us (UME) and many of you, Japanese maple scale (JMS) is a pest of key status this season. Numerous nursery growers and landscapers are discovering high and damaging populations of this little beast (some might have other names for them). We have been monitoring JMS lifecycle for the last two seasons (2009 and 2010). Our data for JMS crawler activity indicates:

1st Generation 2nd GenerationStart Peak Start Peak795 DD 1144 DD 2220 DD 3037 DD

Remember, degree days (DD) are estimates of insect activity (and the above are averaged over only 2 years). You still need to use your hand lens and see what the scales are doing on your trees in your locations. See the end of this report for DD estimates for areas throughout the state.

We have been monitoring JMS on red maples for 1st generation crawler activity. It is time to get ready! Here is what we found as of yesterday (5/26/2011). In College Park, 854 DD had accumulated. When branches with JMS were examined under the microscope the majority of the scales had eggs or eggs that were JUST starting to hatch but still under the female covers. There were also some active crawlers on the branches. These are very small, oval in shape, light purple in color, and had not started to produce any wax yet which indicates they had JUST hatched. In Laytonsville, 771 DD had accumulated. When scale covers were flipped, only eggs were found beneath, no crawler activity was observed. So Laytonsville is a little behind College Park. Note: Crawler activity will vary somewhat with location / climate so monitor your local JMS populations. For example, the Eastern Shore seems to be ahead of us on degree days by a week or two so JMS crawler activity may be further along than in central Maryland.

Control: Target peak crawler activity. Distance and Talus (insect growth regulators, IGR’s) have both provided good control; studies have also shown Arena (neonicotinoid, systemic) to be effective. I (Paula) recommend waiting until you have peak crawler emergence – likely 1 week to 10 days from now if you are in College Park, maybe 2 weeks in Laytonsville – if you are treating with an insect growth regulator (Distance or Talus). JMS crawlers emerge over an extended period of time. If you treat too early with an IGR (ex. Distance or Talus) you may not have the residual control when you have the most crawler activity. If you plan on using a systemic such as Arena I recommend putting that down at the beginning of crawler activity (now if you are in College Park or Laytonsville). This way the Arena should be in the tree by peak crawler activity. Be sure to read the Arena label regarding use limits. Remember that imidacloprid has not been shown to provide good control of armored scales and would not be the best choice for JMS control.

Japanese maples scale eggs (left) and a crawler (right) are purple

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SpittlebugsMarie Rojas is finding spittlebugs on white pines in pretty good numbers in Beallsville. Control: Not necessary. Many natural predators feed on this insect.

BagwormsBob Mead, Mead Tree & Turf Care, Inc., is finding first instar bagworm larvae that are just starting to make bags infesting blue spruce in Howard County. Rick LaNore, MRW Lawns, Inc., is starting to find bagworms smaller than the tip of a pencil in Southern Maryland. Bagworm activity is 2 - 3 weeks earlier this year than usual. Control: At this early stage, Bt is still a good option. Conserve, Orthene, Acelpryn, and Astro all provide good control of bagworms.

Euonymus ScaleWe are finding mainly 2nd instars on euonymus plantings in central Maryland this week. We should see crawlers sometime in late June or early July.

Gloomy ScaleBradley Seay, Bartlett Tree Experts, found gloomy scale on red maple (A. rubrum) on May 25 in Crofton. Also look for this armored scale on dogwood, sweet gum, poplar, catalpa, black locust, willow and grape. The females are circular and brown to gray. The males are more elongated and black in color. There is one generation per year in Maryland and egg laying occurs in July and continues through August.Control for Gloomy Scale and Euonymus Scale: A mixture of 1% horticultural oil and Distance could be used on small trees when crawlers are present. Dinotefuran (Safari) applied as a soil drench also control these pests.

The twolined spittlebug is another species found in this area

Pine spittlebugPhoto: Lacy L. Hyche, Auburn University, Bugwood.org

Scale (Pulvinaria spp.) on Hibiscus and Chinese HollyMarie Rojas found high numbers of a scale (Pulvinaria sp.) on hibiscus in a landscape in Laytonsville. Steve Sullivan, The Brickman Group, is finding cottony camellia/Taxus scale on Chinese holly this week.Control: Treat crawlers with the insect growth regulator Distance or oil. Soil injections of imidacloprid (Merit in the landscape, Marathon in nurseries) can be applied in April.

Lecanium ScaleCrawlers of lecanium scale have been observed in central Maryland this week. The crawlers generally migrate out onto the foliage of plants. Control: Talus or Distance with 0.5% horticultural oil would give good control aty this point.

Overwintering femals of lecanium scale on contorted almond

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White Pine AdelgidWhile we were conducting a pest ID session for arborists in Salisbury recently, we came upon a white pine that had a heavy infestation of pine adelgid. The pine bark adelgid, Pineus strobi (Hartig), native to Europe but one of the most commonly reported insect pests of pines in America, feeds on tree trunks by sucking sap from the phloem tissues. It can be problematic for small nursery stock, but if trees are healthy, permanent damage should not result. The primary plant host is the eastern white pine (Pinus strobus), but it occasionally attacks other pines such as the Scotch (Pinus sylvestris), ponderosa (Pinus ponderosa), jack (Pinus banksiana), pitch (Pinus rigida) and Austrian (Pinus nigra) pine.Biological Control: Lady bird beetles, dustywings and hoverflies all feed on pine bark adelgid. If beneficial predators are present, use insecticides such as insecticidal soap or horticultural oils that will have less of an impact on the beneficials. Pest populations should be closely monitored. Chemcial Control: Dormant oil sprays and insecticides are effective in killing overwintering nymphs if applied in the fall or spring before nymphs mature and lay eggs.

White pine adelgids coat the branches of this white pine

Fire Blight Fire blight is still very evident, showing up on crabapples, ornamental pears, Asian pears and apple trees this week. Marie Rojas noted that fire blight is starting to show up on PristineTM apples in Beallsville. We are receiving emails and phone calls from several places in the state reporting that dieback is just starting on tip growth. When we have some dry weather, prune several inches (at least 12 – 18”) below the dieback section on the branches. Rainy weather will spread this bacterial disease.

Honeylocust Plant BugSteve Sullivan is reporting that honeylocust plant bugs are active in central Maryland this week. You can check for nymphs by tapping the foliage over a white piece of paper. Honeylocust plant bugs overwinter as eggs just below the bark surface, usually on twig growth. The eggs hatch just as the vegetative growth of the honeylocust starts to open. The nymphs move from the woody twig tissue to the newly emerging green growth and start to feed. Most of the damage that will show up later in the season occurs at this early feeding time.Control: Use a 1% rate of horticultural oil or apply soil applications of dinotefuran (Safari).

Honeylocust plant bug damagePhoto: Steve Sullivan, The Brickman Group

Locust LeafminerAdult feeding by locust leafminers is beginning in the area at this point. Brian Clark, UMD, found locust leaf miner last week in LaPlata. We are starting to see damage on black locusts here in Ellicott City as well. At this time of year, the damage by the adults is minimal. It is the feeding by the larvae later in the season that causes significant damage to the trees.Control: Not necessary. This native tree often leafs out again later in the season.

Damage on foliage by adults in July 2007

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Grape growing along a building with a wine shop.

Potato LeafhopperLast week, Dave Clement and I were conducting a pest ID training for arborists in Salisbury. During the training we found red maples with potato leafhoppers in large numbers on the foliage. The Eastern Shore is generally about 10 days to 2 weeks ahead of central Maryland. Control: If you have a nursery, start monitoring for potato leafhopper now and an application should go on very soon. Applications of TriStar, Acephate (Orthene) or Flagship can be used to control this pest.

Innovative Grape GrowingWhile in Salisbury we walked by a wine shop that is growing wine grapes against a wall surrounded by concrete. The vines had been growing at the site for over 10 years. Grapes are very tough plants and grow in some very adverse conditions sometimes... a very clever use of plants to sell wine.

Leaf spots of Entomosporium on both the upper and lower leaf surfaces

Entomosporium Leaf SpotGreg Dionne, Mainscapes, Inc., brought in a sample of red tip photinia that is infected with Entomosporium leaf spot. This fungal pathogen (Entomosporium maculatum) infects new growth of photinia, some pear cultivars and other members of the rose family. Look for dark red spots on the upper and lower leaves of the foliage. Severe infections can cause defoliation and the death of the plant.Management: Avoid getting foliage wet as much as possible when watering the plants. Remove infected foliage from the planting area. Also, avoid pruning which generates new growth which is more susceptible to infection. Apply fungicides as long as there is new growth on the plants. Fungicides for control include Banner, Daconil 2787 75W, Daconil 2787 4.1F, Fore 80W, Bayeleton 25W and Funginex EC.

Lesser Peachtree Borer, Synanthedon pictipesThe adult clearwing moth of lesser peachtree borer is still being found in my pheromone traps in the Westminster area (Carroll County) this week. Chemical Control: Chemical control is preventive when insecticide is applied to trees before borer eggs hatch so that small borer larvae contact a toxic residue as they crawl into trees. Control may also be achieved by fumigant action of the insecticide, which can kill larvae already in trees at the time of application. An insecticide with long residual action gives the best control of borers. Thorough coverage is necessary. Insecticide should be applied as a bark drench to the trunk and scaffold branches at a rate of at least one-half to one gallon of spray mix per tree. Carbaryl (Sevin) is labeled for borer control in home peach plantings.

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Emerald Ash Borer And Purple TrapsWe have had several inquires about the large, purple, triangle-shaped traps hanging in trees near highways and other roads. These are attractant traps for adult emerald ash borer that MDA placed out. They place them in the canopy of trees where people will leave the traps alone. The traps are regularly checked by MDA for adult beetles attracted to the purple color to find out if emerald ash borer is active in counties other than Prince George’s and Charles counties. Adults are out and flying this week.

One of the species of sawflies feeding on a rose leaf along with an aphid

Lady bird beetle larva found on spirea

Beneficial Insect Activity in the LandscapeWe are receiving regular reports of beneficial activity by insects such as lady bird beetles and syrphid fly larvae.Steve Sullivan is finding lady bird beetles feeding on aphids that are infesting burningbush euonymus. Rachel Melvin, University of MD Extension in Queen Anne’s County, is reporting that there are plenty of lady bird beetles feeding on the spiny witchhazel gall aphids infesting birch trees. Another sample of spirea was brought to the office this week that had a syrphid fly larva, a lady bird beetle nymph and an aphid mummy (sign of parasitic wasps) present. And, here at the research center, a syrphid fly larvae was found on a small population of aphids on roses. If you treat for aphids, use an insecticide that will have minimal impact on the beneficial insects present.

Lady bird beetle eggsPhoto: Rachel Melvin, UME

Sawflies on RosesWe are receiving reports of sawflies damaging roses this week. There are three species found in this area: roseslug sawfly, curled roseslug sawfly and bristly roseslug sawfly. Early instar larvae cause small holes in foliage. Feeding by later instars creates larger holes and can defoliate plants.Control: Roseslugs look like caterpillars but since they are not, some insecticides such as Bacillusthuringiensis will not kill them. Conserve or Orthene can be used to control the larvae.

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Beneficial of the Week, Paula ShrewsburyWheel bugs are hatching and looking for prey to assassinate

Assassin bugs are true bugs (Heteroptera) in the family Reduviidae and are very important predators of a diverse array of pest insects found feeding on ornamental plants. There are numerous species of assassin bugs, but one of the more common is the wheel bug, Arilus cristatus. This particular assassin bug gets its common name, wheel bug, because of the spoke bearing, wheel-like structure on its pronotum (section behind the head). They are large bugs with adults reaching 1- 1.5”. Wheel bug adults and immatures are generalist predators that feed on a diversity of insects such as caterpillars, plant hoppers, sawfly larvae, aphids, and beetles. The wheel bug approaches its prey, quickly grabs it with its front legs, and then impales the insect with its beak. Through its beak the wheel bug injects digestive enzymes which liquefy the body tissues of the prey making it possible for the predator to suck up its food. Last autumn female wheel bugs were laying clusters of 10-40 eggs on the bark of trees. Now that winter is over and the warm weather is here the eggs are hatching. Nancy Harding (UMD Entomology) has seen numerous red and black nymphs on the bark of trees, especially maples, this last week or so. Nymphs and then adults are active through most of the growing season helping to control pest insect populations. If you see these red and black nymphs on your trees consider yourself lucky. With their voracious appetite they will help keep some of the plant feeding insects from reaching damaging levels.

For more information on wheel bugs and a great video of a wheel bug attacking a caterpillar, go to Bug of the Week (the November 23, 2009 episode) at: http://www.raupplab.umd.edu/

A wheel bug adult female lays a cluster of eggs at Raemelton Farm during the fall of last year. Note the distinct “wheel” from which this assassin bug gets its name. Photo: Mike Raupp, UMD

Wheel bug egg mass with newly hatched nymphs dispersing in search of preyPhoto: Mike Raupp, UMD

Weed of the Week, Chuck SchusterWild radish, Raphanus raphanistrum, is a winter annual that can be found in nurseries, landscapes, and occasionally turf throughout the United States. Introduced from Europe, it has become a weed that requires some attention. It germinates in the fall when soil temperatures drop to 65 °F or lower. The cotyledons are on petioles and are heart-shaped. The first true leaves have a toothed margin, lobed and are hairy. Research has shown that cold temperatures are required to break dormancy. The initial basal rosette will produced lobed leaves, are elliptical in shape, up to ten inches in length and two inches on width. The root system is a taproot, and will have a distinct odor and taste of a radish. Each basal leaf occurs on a petiole. As warmer temperatures occur the rosette will bolt to an upright stem. Stem leaves are alternate and without petioles, with a toothed margin and will occur with stiff hairs. The stem, reaching to thirty inches in height, can have multiple flower

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Wild radish in bloomPhoto: Rebekah D. Wallace, Bugwood.org

Plant of the Week, Ginny RosenkranzCornus kousa ‘Wolf Eyes’ is a variegated form of the Chinese dogwood. It grows slowly to a height and width of 10 feet by 10 feet and is considered a broadly spreading shrubby tree, often with multiple trunks. The leaves, like all Cornus kousa, emerge before the flowers in the spring and are wavy edged, variegated gray green with creamy white leaf margins that hold their color in both shade and sun. The blooms emerge a month after the flowering dogwood and are 4-pointed, showy white, star-shaped bracts which will last for almost 6 weeks before fading and falling off the tree. In the fall the orange-red fruit that follows the flowers are raspberry-like in appearance and will last until the birds eat them off the tree. In the fall the leaves develop colorful pink to red streaks in place of the white margins. The bark of older trees develops a mottled look, giving this small tree four seasons of interest. ‘Wolf Eyes’ will grow in many soil types as long as the soils are kept evenly moist and it is hardy in USDA zones 5-8. Insect pests include aphids, borers, scale, leaf miners and diseases include anthracnose, leaf spots and powdery mildew.

heads form from this upright stalk which will also have stiff hairs. Flowers are yellow to white in color, have four petals, and measure between one half inch and three quarter inch in diameter and occur on flower stalks. The fruit produced will be long, measuring up to one and one half inch in length and will break into break apart into fragments. Similar in basic shape to wild mustard, yet occurring with stiff hairs. Control in turf can be gained using many of the 2 4 D and Dicamba products also basamid (Dazmet). In the landscape, use of Trifluralin (Treflan), Dichlobenil (Casoron) can be used as a pre emergent product.

Cornus kousa ‘Wolf Eyes’Photos: Charleen Miller

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PLANT PLANT STAGE (Bud with color, First bloom, Full bloom, First leaf)

LOCATION

Asclepias incarnata Bud (May 27) Ellicott CityGalax aphyla Full bloom (May 26) Silver RunKalmia latifolia ‘Bullseye’ Full bloom (May 26) Silver RunPhysocarpus opulifolius ‘Luteus’ Full bloom (May 26) Silver RunPhysocarpus opulifolius ‘Diablo’ and ‘Coppertina’

Full bloom (May 26) Wheaton

Rhododendron maximun ‘Roseum’ Full bloom (May 26) Silver RunSalvia ‘May Night’ Full bloom (May 26) Silver RunScutellaria serrata Full bloom (May 26) Silver RunSyringa ‘Herr’ Full bloom (May 26) Silver Run

Degree Days (As of May 26)

Baltimore, MD (BWI) 715 Dulles Airport 690 Frostburg, MD 358 Martinsburg, WV 605 National Arboretum 810 Reagan National 782 Salisbury 757

Stanton GillExtension Specialist

sgill@umd.edu

Paula Shrewsbury Extension Specialistpshrewsb@umd.edu

Ginny RosenkranzExtension Educatorrosenkrnz@umd.edu

Chuck SchusterExtension Educator

cfs@umd.edu

Karen Rane Plant Pathologistrane@umd.edu

Brian Clark Extension Educator bpclark@umd.edu

Andrew RistveyExtension Specialistaristvey@umd.edu

David ClementPlant Pathologist

hgic.umd.edu

The information given herein is supplied with the understanding that no discrimination is intended and no endorsement by University of Maryland Extension is implied.

CONTRIBUTORS:

University of Maryland Extension programs are open to all citizens without regard to race, color, gender, disability, religion, age, sexual orientation, marital or parental status, or national origin.

Thank you to the Maryland Arborist Association, the Landscape Contractors Association of MD, D.C. and VA, the Maryland Nursery and Landscape Association and FALCAN for your financial support in making these

weekly reports possible.

Upcoming Programs:

June 2, 2011 Pest WalkLocation: Carroll County Extension Office, Westminster, MDContact: 410-321-8082

June 3, 2011Pest Management Conference for RecertificationLocation: Eastern ShoreContact: 410-749-6141

June 10, 2011Procrastinator’s Pest Management ConferenceLocation: Montgomery County Extension Office, Derwood, MDContact: 301-590-2807

June 23, 2011MNLA Field DayLocation: Priapi Gardens, Cecilton, MDContact: 410-823-8684

June 25, 2011 (Saturday)Summer Maryland Christmas Tree Association MeetingLocation: Sewell’s Tree Farm, Taneytown, MDContact: 410-452-9793