for Arborists, Landscape Managers & Nursery Managers

Commercial Horticulture April 26, 2013Coordinator 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) 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 update- Fasciation- Emerald ash borer- Scale update- Predaceous caterpillar- Witchhazel gall aphid- Pearleaf blister mite- Japanese beetles- Chiggers- Eastern tent caterpillar- Spruce spider mite- Gypsy moth- Sapsucker/European hornet comments- Daylily leafminer

Weed of the WeekPlant of the WeekJob announcementDegree DaysPhenologyConferences

Integrated Pest Management for

Commercial Horticulture

ipmnet.umd.edu

Weather Update - Frost DamageOn the morning of April 20th, we had frost reported in Westminster and Finksburg (Carroll Co.), Beltsville (Prince George’s Co.), Federalsburg (Caroline Co.), and Woodbine (Howard Co.). Marty Adams noticed considerable frost damage on Halesia trees. The damage appeared to be sustained on April 19th in Silver Run (Carroll Co.) - the blooms only partially opened and turned mushy. He noted that, interestingly, it seemed like the peduncles sustained most of the damage with the flowers hanging limply.Temperatures only went down to about 35 °F, but there was frost evident on blooms and tips of new growth. New plant growth may show necrotic tip growth. We typically see lilac with black new leaves after a late frost.

Fasciated dandelion flowerPhoto: Mike Little

Strange Dandelion Flower StalkMike Little sent a photo of a strange-looking dandelion flower. It is called fasciation which is a relatively rare condition of abnormal growth in vascular plants. It may occur in the stem, root, fruit, or flower head. Some plants are grown and prized aesthetically for their development of fasciation. Fasciation has several possible causes, including hormonal, genetic, bacterial, fungal, viral and environmental.

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Emerald Ash Borer (EAB)We have received several calls from landscapers and arborists about emerald ash borer control. As EAB continues to spread on the westernshore of Maryland there is growing interest in protecting really valuable ash trees in the landscape, especially ones that would cost a lot to remove if they become infested. I contacted Dr. Dan Herms, Ohio State University, for an update on control options. Dan Herms was a guest speaker in December at our IPM Pest Management Conference and spoke on EAB control. Dan shared a chart they published on control options.

Insecticide Formulation Active Ingredient Application Method Recommended TimingProfessional Use Products

Merit® (75WP, 75WSP, 2F) Imidacloprid Soil injection or drench Mid-fall or mid- to late spring

XytectTM (2F, 75WSP) Imidacloprid Soil injection or drench Mid-fall or mid- to late spring

IMA-jet® Imidacloprid Trunk injection Early May to mid-JuneImicide® Imidacloprid Trunk injection Early May to mid-JuneTREE-ägeTM Emamectin benzoate Trunk injection Early May to mid-JuneInject-A-Cide B® Bidrin® Trunk injection Early May to mid-JuneSafariTM (20 SG) Dinotefuran Systemic bark spray Early May to mid-JuneAstro® Permethrin Preventive bark and

foliage cover sprays2 applications at 4-week intervals; first spray should occur when black locust is blooming (early May in southern Ohio to early June in mid-Michigan)

Homeowner FormulationBayer AdvancedTM Tree & Shrub Insect Control

Imidacloprid Soil drench Mid-fall or mid- to late spring

Table 1. Insecticide options for professionals and homeowners for controlling EAB that have been tested in multiple university trials. Some products may not be labeled for use in all states. Some of the listed products failed to protect ash trees when they were applied at labeled rates. Inclusion of a product in this table does not imply that it is endorsed by the authors or has been consistently effective for EAB control. This chart is in the publication “Insecticide options for Protecting Ash Trees from Emerald Ash Borer” atwww.emeraldashborer.info/files/multistate_eab_insecticide_fact_sheet.pdf

Planning for the Invasion: Control Measures for Emerald Ash Borer for Managers of Urban Forest ResourcesIf you are a city manager and need to make decisions on how to deal with EAB in your city then look into attending the May 7th conference More information is available at http://eabcontrol.eventbrite.com/

Scale UpdateAs of Tuesday, April 23rd, Nancy Harding, UMD, examined white prunicola scale (WPS) and Japanese maple scale (JMS) from Yoshino cherries in Laytonsville and found the following: JMS - 2nd & 3rd instar females w/no eggs and WPS - 3rd instar females w/no eggs. Marie Rojas is also not seeing any eggs yet. This indicates that there will not be crawlers for some time, we will keep you updated. Betsy Carbo, Library of Congress, found Indian wax scale on Artemisia last week in Washington, DC. Betsy noted that it was a small enough number that she physically removed the adults.

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The predaceous caterpillar, Laetilia coccidivora, feeding on tuliptree scale

Caterpillar That Feeds on Soft ScaleWe had an inquiry about biological control of tulip tree scale. We have observed a predacious caterpillar, Laetilia coccidivora, feeding on tuliptree scale. Whether this caterpillar can redcue a population is questionable but interesting.

Witchhazel Gall AphidMarie Rojas, IPM Scout, and Craig Greco, Yardbirds, Inc., are reporting spiny witchhazel gall aphids and some damage on birch this week. Marie found the activity in Beallsville on April 24. This aphid causes red puckering damage to the foliage of birch and the woolly aphids can be found on the undersides of the leaves. It causes spindle galls on its alternate host which is witchhazel.Control: Most often, control is not necessary. Many natural enemies such as lady bird beetles, syrphid flies, soldier beetles, and parasitic wasps are active this time of year and usually move into the area to reduce the aphid populations. If populations are high, use a low impact material like horticultural oil to minimize the effect on the beneficial insects that are present.

Pearleaf Blister MiteMarie Rojas, IPM Scout, found damage from pearleaf blister mite starting to show up on Bradford pears in a landscape in Gaithersburg. Control: Nothing at this time of the year. If necessary, overwintering females can be controlled with applications of sulfur applied just after leaf drop in October.

Damage on birch from witchhazel gall aphidPhoto: Craig Greco, Yardbirds, Inc.

Lady bird beetle eggs and witchhazel gall aphids

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Japanese Beetles – In JuneFrom: Stanton GillRemember last summer when we had rainfall in late July and August just about the time Japanese beetles females were laying their eggs? Well, chances are that we will see a fair number of adult Japanese beetles starting in June and continuing for 4 to 6 weeks this summer.

When they show up in large numbers we see a lot of plant material such as roses, azaleas, linden trees, cherry trees, and crabapples with beetles clustering and feeding heavily on the foliage. When we had the last big outbreak of Japanese beetles in 2004 and 2005 many people were using carbaryl (Sevin), Acephate (Orthene), several pyrethroids such as Permethrin (many Product names) and bifenthrin (Talstar) . Also several people were using imidacloprid as soil and trunk injections on Linden trees for control. I contacted Dr. Dan Potter at Kentucky University. I know he had been testing several materials for Japanese beetle control.

Dr. Jason Oliver, Tennessee University, provided this information: Surround Kaolin clay will also reduce adult Japanese beetle feeding if landscape customers are willing to tolerate their plants being white for a period of time. Might be useful to reduce feeding damage during peak flight periods. Since it is just clay, it should be fairly low impact on beneficials.

Neem ProductsIn trial with Neem products we conducted at CMREC in 2005 and 2006 we could deter adult Japanese beetles from feeding on foliage if treated with neem for about 3 – 4 days. Dan Potter found similar results in his trials in Kentucky.

ChiggersWe received a few emails asking about chiggers. Chiggers have started activity in tall grass areas. In many nurseries if you let the grasses and weeds grow up, you may experience a run-in with chiggers. Keep the tall grasses and weeds mowed regularly and you will avoid a lot of problems.

For detailed information on chiggers, go to http://animal.discovery.com/arachnids/question488.htm

Chigger mitePhoto: Susan Ellis, Bugwood.org

Daylily LeafminerGaye Williams, MDA, is reporting that according to her 2012 daylily leafminer entries, the first adult flies were seen on May 11th after she had made 3 - 4 earlier, weekly trips to her test garden in Davidsonville. Gaye reports that the first mines, at that point approximately 6 inches long, were observed on May 25. She points out that the flies overwinter as puparia at leaf bases and need to mate and lay eggs before new mines appear.

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Eastern tent caterpillars on cherry laurelPhoto: Craig Greco, Yardbirds, Inc.

Spruce spider mite damage on juniperPhoto: Karen Rane, UMD

Spruce Spider MiteGreg Clontz, Mainscapes, Inc., brought in a sample of prostrate juniper that had a lot of damage from spruce spider mites on the foliage from last season. We found a lot of eggs, but no hatched nymphs yet. Using a 10x hand lends, monitor spruce and junipers for spruce spider mites on branches. Place a clipboard with a piece of light colored paper under branches and rap the branch on the paper to examine for hatching mites. You might have egg hatch if you are in a city area or on the Eastern Shore. The sample we received was from central Maryland and there were no hatched eggs at this point.Control: Horticultural oil, Hexagon (a mite growth regulator that is very effective early in the season killing young spider mites with minimal impact on beneficials), Avid, and Sanmite.

Eastern Tent CaterpillarsThe cooler than normal weather is making tent caterpillar activity stretch out over a long period. Marie Rojas, IPM Scout, and Debby Smith-Fiola, Landscape IPM, reported Eastern tent caterpillars are active in Frederick County and Washington County this week with early instar caterpillars just starting to create webbing and starting to feed on cherries and crabapples. Last year at this time they were finishing up development and starting to migrate to pupation sites. We are still about 3 - 4 weeks behind insect activity this season.Control: The early instar caterpillars are easy to kill with Bt, Conserve, Acelpyrn, or even insecticidal soap at this point.

Eastern tent caterpillars under silk along stemPhoto: Debby Smith-Fiola, Landscape IPM

Gypsy MothGypsy moths have become less of a noticeable problem in most parts of Maryland. In 2013, Maryland Department of Agriculture will be spraying areas in Garrett, St. Mary’s and Worcester counties. Sprays are currently scheduled for St. Mary’s and Worcester counties on May 2nd. Date(s) have not been posted for areas in Garrett County yet.

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Sapsucker/European Hornet CommentsComments in response to photos in a recent report of the damage on plants that could be from sapsuckers or European hornets.

From Bob Trumbule, MDA: I have just read the latest TPM/IPM report and saw the sapsucker vs. other taxa causing damage on hollies and viburnums debate. First of all, I am pretty sure that sapsuckers are “woodpeckers” (but not all woodpeckers are sapsuckers), so there should be no issue differentiating between the two there. Also, European hornets don’t cause holes like those pictured. I have northern flickers and hairy and downy woodpeckers that hang around all winter in my garden. I have never seen them attacking tree or shrub stems, although the flickers do like to feast on the bee larvae in my mason bee houses! I have extensive damage to hollies (especially I. x aquifolium ‘Lassie’) and viburnums at my place and it looks just like what is pictured in last week’s TPM/IPM report. Since I don’t see the birds that overwinter doing the damage, I always assumed that it was done by migratory sapsuckers. I think you are correct in calling the damage shown in those photos sapsucker damage.

From Steve Sullivan, The Brickman Group: In regards to the sapsucker damage and if that is what is causing the damage in the last report. I would completely concur that it is sapsucker damage on the viburnum. They are common on it and I have seen plenty of it in the landscape. While they often do hit maples, I am not positive that damage seen in the report is sapsucker.

Weed of the Week, Chuck SchusterWarmer weather with adequate soil moisture is providing a wide array of color this spring. Golden ragwort, Packera aurea formerly Senecio aureus, is being found abundantly in the landscape at this time of year. Reported in both Montgomery County and the lower Eastern Shore, this plant may also be called golden groundsel or butterweed. A member of Asteraceae (Aster Family), it is a perennial and produces rhizomes. The large basal leaves are dark green on the upper surface and purple on the underside and will support the one to three foot tall, erect flowering stem. The flowering stems have lobed leaves. The flowers are yellow, aster-like, and about one inch in diameter. The fruit is brown. The plant has a spreading habit and can choke out other plant species. Golden ragwort does not grow well in dry soils and prefers full to partial sun. This plant can be poisonous to livestock.

Manual removal of this plant is difficult as a portion of a rhizome will create a new plant. This plant does not propagate well by seed, but spreads quickly with rhizomes. Post emergent control in landscapes can be achieved using glyphosate based products, always using caution near desired species of plants. Tordon Max is labeled in right-of-way settings. Golden ragwort in bloom

Photo: William Monroy

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Cercis canadensis ‘Alba’Photos: Ginny Rosenkranz, UME

JOB POSTING/HELP WANTED: University of MarylandTitle: Associate Agent Functional Title: Master Gardener Trainer, Sustainable HorticulturePosition Number: 118930 Location: Ellicott City, MDClosing date will be 5/6/13 or until filled

Position Summary/Purpose of Position:The Master Gardener Trainer will develop, implement, and provide advanced training (face-to-face and online) for Master Gardeners in ornamental plants with an emphasis on native plants and sustainable landscaping. Create new content on the HGIC website, and develop online teaching modules. Provide support for HGIC horticulture consultants. Work as a team member with State Master Gardener Coordinator and Advanced Training Coordinator to determine training needs and methods of delivery and evaluation.

Application Process: All candidates must apply online at https://ejobs.umd.edu.

Plant of the Week, Ginny RosenkranzCercis canadensis ‘Alba’ is exactly like the normal native redbud except the pea-shaped flowers are completely white. Redbuds bloom in March to April. In the wild, native redbuds brighten up the outer fringes of the woods with bright pink to purple flowers that completely cover the tree before the leaves emerge. The tree can grow 20-30 feet tall with a spreading, horizontal branching habit and flat-topped silhouette. The branches grow in a zigzag pattern with the leaves emerging at each turn. The bark is dark brown when young and slightly shaggy as it matures. The leaves are bright green and heart-shaped. A year old seedling planted in a garden with morning sun and afternoon shade grew from 8 inches tall in the spring when planted to 3 feet tall by fall and thrived due to consistent watering during dry spells throughout the summer. They will have to mature for a few more years before they will burst into bloom with one half inch pink/ purple (or with ‘Alba’, pure white) flowers that last in a cool spring for almost a month before the heart-shaped leaves begin to emerge. ‘Alba’ leaves are light green without any purple coloring and turn a bright yellow in the fall. ‘Royal White’ is a cultivar with pure white flowers that are slightly larger and open slightly earlier. It is more cold tolerant than the straight species. After flowering, the plant produces 2-3 inch pods that start out green then mature to brown which hang on the tree all through the fall and winter. The plants grow in USDA zone 4-9. All Cercis canadensis prefer to be planted in moist, well drained soils, and in full sun to partial shade with adequate watering to prevent stress that leads to canker diseases. They are tolerant of both acidic and alkaline conditions. Leaf spot and Verticillium wilt are disease problems. Leafhoppers, treehoppers, caterpillars and scale are the insect pests.

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

LOCATION

Amelanchier nantucketensis Full bloom Silver Run (April 22)Amelanchier fernaldii Full bloom Silver Run (April 22)Cercis canadensis Full bloom Salisbury, Columbia (April 23)Croton alabamensis Enkianthus perulatus ‘JL Pennock’ Full bloom Silver Run (April 22)Epimedium grandiflora koreana ‘La Rocaille’

Full bloom Silver Run (April 22)

Epimedium pinnatum ‘Colchicum’ Full bloom Silver Run (April 22)Rhus aromatica Full bloom Silver Run (April 22)Hydrastis canadensis First bloom Silver Run (April 22)Podophyllum peltatum (mayapple) Full leaf and bud Columbia (April 25)Prunus serrulata ‘Kwanzan Full bloom Salisbury (April 23)Stylophorum diphyllum Full bloom Silver Run (April 22)Syringa vulgaris Full bloom Salisbury (April 26)Trillium grandiflorum Full bloom Silver Run (April 22)Viburnum rhytidophyllum Bud Ellicott City (April 26)Xanthoriza simplicissima Full bloom Silver Run (April 22)

Plant Phenology: What is in bloom

Degree Days (As of April 25)Baltimore, MD (BWI) 191 College Park 266Dulles Airport 223 Frostburg, MD 107 Martinsburg, WV 198 National Arboretum 266 Reagan National 266 Salisbury 263

To check degree day (DD) accumulations in your local area go to: http://www.weather.com/outdoors/agricul-ture/growing-degree-days/USMD0100

Stanton GillExtension Specialist

sgill@umd.edu

Paula Shrewsbury Extension Specialistpshrewsb@umd.edu

Ginny RosenkranzExtension Educatorrosnkrnz@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, Professional Grounds Management Society, and FALCAN for your

financial support in making these weekly reports possible.

Photos are by Suzanne Klick or Stanton Gill unless stated otherwise.

Upcoming Programs

MNLA Nursery Field DayJune 20, 2013Location: Waverly Farm, Adamstown, MDContact: MNLA, 410-823-8684

Planning for the Invasion: Control Measures for Emerald Ash Borer For Managers of Urban Forest Resources May 7, 2013 Location: Robinson Nature Center, 6692 Cedar Lane Columbia, MD 21044 http://eabcontrol.eventbrite.com/

Nutrient Management Plan Writing – Nursery and Greenhouse ProductionJuly 10, 2013, 9 a.m. to 3:30 p.m.Location: CMREC, 11975 Homewood Road, Ellicott City, MD 21042Contact: Andrew Ristvey, aristvey@umd.edu, 410-827-8056 x113

Improving Your Diagnostic and Treatment Skills: An Evening SeminarMay 29, 2013Location: CMREC, Ellicott City, MD