for Arborists, Landscape Managers & Nursery Managers

Commercial Horticulture June 5, 2015Coordinator 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 Nancy Harding, Faculty Research AssistantDisease 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 (Extension 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- Emerald ash borer- Boxwood spider mites- Scale update- Bagworms- Spittlebugs- Gypsy moth- Eastern tent caterpillars- Rose rosette disease- Red thread in turf- Galls on maple and elm- Hibiscus sawfly- Penn State disease update

Beneficial of the WeekWeed of the WeekPlant of the WeekPhenologyDegree DaysAnnouncements

IPMnetIntegrated Pest Management for

Commercial Horticulture

extension.umd.edu/ipm

Finally Some RainBy: Stanton Gill, UMEThe rain this week helped quite a bit, but we are still falling short on rainfall for the late spring. Get the trickle irrigations system going in your customer’s landscapes. For Baltimore, we received just a little more than half of the normal rainfall for the month of May. With this week’s rain, June is one half inch away for its normal monthly amount of rainfall.

These emerald ash borer adults are from an infested ash tree in a parking lotPhoto: Todd Armstrong, Davey Tree Experts

Emerald Ash BorerBy: Stanton Gill, UMELast week we had several reports and emailed pictures of adult emerald ash borers (EAB) in Montgomery and Frederick Counties. So far, this beetle has not been found on the Eastern Shore. If you find a suspicious beetle, send us a sample or electronic picture. Steve Nagy, Davey Tree Experts, reports trapping and catching EAB in the Germantown and Gaithersburg areas in the past two weeks. Todd Armstrong, Davey Tree Experts, and Amanda Ramey, National Park Service, found an EAB infestation on ash in Glen Arm.

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Monitor plants closely in early July for the start of the second generation of crawlers of white prunicola scale

Boxwood Spider Mites (Eurytetranychus buxi)Monitoring Buxus sempervirens in College Park for boxwood spider mite found the first flush of egg hatch on May 27. The cumulative Degree Days were 546DD.

Adults are the size of a period, long legged, and yellow-tan in color. Eggs are light yellow until near hatching, when they become dark yellow-brown. Immatures look similar to adults, but smaller. There are several generations a year. Boxwood spider mites prefer European, common and English boxwoods. Mite feeding causes a yellow stippling or streaking appearance on leaves. In heavy infestations, entire leaves may turn mostly yellowish white and drop prematurely.

Control: Control light summer infestations with a 1 to 2% insecticidal oil or soap sprays. For heavy infestations, use residual or foliar absorbed miticides. Reduced risk miticides including bifenazate (Floramite), spirotetramat (Kontos), and spiromesifen (Forbid) are labeled against mites.

Boxwood spider mite female with eggPhoto: Rayanne Lehman Bugwood.org

Double-sided tape can be wrapped around trunks of trees to monitor for Japanese maple scale crawlers; Use a hand lens to look for the crawlers

Scale Update

Japanese Maple ScaleWe received a report from Frederick County that Japanese maple scale crawlers were found on June 4. Degree days were 840. Use a hand lens to look for the light purple crawlers. Double-sided tape can be wrapped around trunks of trees and then checked regularly to determine when crawlers are active.Control: Applications of 0.5 - 1% horticultural oil and pyriproxyfen (Distance) or buprofezin (Talus) should be made when crawlers are detected. This treatment should have about 2 - 3 week residual activity. At that time monitor your plants again to see if crawlers are still active. The twice-stabbed lady bird beetle provides some biological control of this scale.

White Prunicola ScaleWhite prunicola scale is finishing up the first generation of crawlers. The scale is in the second instar stage now. The next crawler stage will be active in early to mid July. Preferred hosts include Prunus, especially lilac, Japanese flowering cherry, and privet. There are three generations of this scale each year.

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Eastern Tent CaterpillarsClaire Porterfield found high numbers of eastern tent caterpillar cocoons on pots and flats at her farm in Delaware. The adult moth will be active in July and will lay new egg masses on branches at that time. The newly laid egg masses should be pruned off to prevent a hatch out next season.

Gypsy Moth CaterpillarCharlie Hogan, UMBC, found a gypsy moth larva on American beech. Trees not preferred by young caterpillars, but which can be attacked by older larvae include maple, hickory, dogwood, walnut, black gum, beech, pine, hemlock, cherry and elm.

Eastern tent caterpillars are pupating now and are no longer feeding on treesPhoto: Claire Porterfield

Spittlebugs can be found on plants throughout the landscape

This late instar gypsy moth caterpillar was found on American beechPhoto: Donna Anderson, UMBC

SpittlebugsThis year seems to be another year when more spittlebugs than usual are active on plants in the landscape. Chris Erb, Complete Lawn Care, found them on river birch last week. Spittlebugs have a wide plant host range. Adults do not produce spittle and quickly jump and fly if disturbed. Generally, it is not an insect that warrants control measures.

BagwormsJonathan Cowherd, Bartlett Tree Experts, found bagworms feeding on Leyland cypress and surrounding willow oaks near Federalsburg on June 3. Tom Hartland, The Brickman Group, found active bagworms on May 29 in Westminster. Monitor your customers’ sites this week forbagworms on susceptible plants such as arborvitae, spruce, and Leyland cypress. Bagworms also infest deciduous trees, but the damage is usually less evident.Control: Check to make sure eggs have hatched before making any treatments. Bt (Dipel, Caterpillar Attack), Spinosad (Conserve) or Acelepyrn will all give good control of young larvae.

Rose Rosette DiseaseMark Schlossberg, ProLawn Plus, Inc., is finding roses infected with rose rosette disease in Ruxton. The causal agent is a virus which is spread by an eriophyid mite. Look for distorted new growth and clusters of shoots that are often reddish in color, and stems with excessive thorniness. Infected plants do not generally recover and plants found to be diseased should be removed from the landscape.

Look for clusters of shoots that are reddish in colorPhoto: Mark Schlossberg, ProLawn Plus, Inc.

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The galls on this slippery elm were caused by eriphyid mitesPhoto: Martin Heidel, Arader, Tree Service

Maple bladder gall is caused by an eriophyid mitePhoto: Tony Murdock, Fine Pruning

Hibiscus SawflyGinny Rosenkranz, UME, found hibiscus sawflies active on hibiscus in Salisbury on June 3. There are no signs of larvae at this time on plants here at the research center in Ellicott City. Monitoring: Examine the undersides of foliage for the presence of the green colored larva. Look very carefully – they camouflage well. Look for defoliation damage. Control: Spinosad works well. Bifenthrin also gives good control but must be directed to the undersides of the foliage.

Galls on PlantsMaple:Tony Murdock, Fine Pruning, found galls on maple which are caused by the maple bladdergall mite (an eriophyid mite). These galls are not a problem for the overall health of the tree so control is usually not necessary.

Elm:Martin Heidel, Arader Tree Service, found galls on slippery elm in Valley Forge, PA. These galls are caused by eriophyid mites. The damage is already done so there is nothing to do about it now. Since most of the time galls do not affect the overall health of the tree and treatment timing (bud break for many gall makers) is so critical, control is not recommended.

Red thread disease is active during cool weatherPhoto: Mark Schlossberg, ProLawn Plus, Inc.

Red Thread Disease in TurfMark Schlossberg, ProLawn Plus, Inc., is reporting that red thread was active in turf in Cockeysville on June 4. Cool (65 - 70 °F), wet weather provides optimum conditions for the development of red thread disease in the spring and fall. Red thread disease is caused by the fungal pathogen, Laetisaria fuciformis. Red thread can reduce turf density and lead to invasion by crabgrass and other weeds. It should not be much of a problem after the weather warms up.Management: Red thread tends to cause more damage to poorly nourished lawns. Maintaining adequate nitrogen levels will often reduce the problem. However, high nitrogen levels can create problems with other turf diseases. If the infection warrants treatment, fungicides include Bayleton, Banner MAXX, Chipco26GT, Compass, Curalan, Daconil Ultres, Headway, Heritage and Insignia.

Hibiscus sawfly larvae blend in well with the foliage

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Disease Update from Penn State: Keep Alert For Scab And Fire Blight Infection This Week For an update on apple scab, fire blight, cedar apple rust, cherry leaf spot and bacterial leaf spot, go tohttp://extension.psu.edu/plants/tree-fruit/news/2015/disease-update-keep-alert-for-scab-and-fire-blight-infection-this-week

Flower or syrphid flies feed on nectar when they are adults. These true flies mimic bees. Photo: M. J. Raupp, UMD

Beneficial of the WeekBy: Paula Shrewsbury, UMD

Aphids attract a suite of natural enemies!At this time of the season there are a number of aphid species active on various plant species. Most commonly at this time of year we see an abundance of rose (Macrosiphum rosae) or potato (M. euphorbiae) aphids on roses, and spirea aphid (Spirea spiraecola) on spirea, and crapemyrtle aphid (Tinocallis kahawaluokalani) are getting going on crapemyrtles. Aphids are usually found on the new growth of plants where the growth is soft and filled with amino acids that provide nutritious food for aphids. Aphids have evolved to become quite efficient aphid making organisms that reach high densities quickly. For example, during the season all aphids are females so every individual in the population is reproducing, they give live birth so no time needs to be spent in the egg stage, and they are parthenogenic so females do not have to mate to reproduce… pretty amazing insects. Even with these attributes however, the nice thing about aphid infestations is that in many situations chemical controls are not needed because there is a suite of natural enemies that ultimately reduce, and often eliminate, aphid populations.

The aphid natural enemy complex includes various species of lady beetles, predatory flies such as syrphid or flower flies and Aphidoletes midges, lace wing predators, and parasitic wasps. I frequently monitor plants for populations of aphids and their natural enemies (always interesting to watch!). The general pattern I repeatedly see is aphid populations building up to pretty high densities, followed by the appearance of various predators and parasitoids, and then a reduction aphid densities, often to just a few or no aphids left on a plant. Natural enemies move into landscape plantings in response to increased “food” being available. There is a suite of natural enemies that are very efficient at finding populations of aphids and knocking back their numbers to near zero. In observations this week, flower (or syrphid) fly larvae and multi-colored Asian lady beetle adults and larvae were found in abundance on the spirea plants happily feeding on the aphids. There were also numerous “aphid mummies” which are aphids that have been parasitized (and killed) by tiny wasps. Particularly abundant were the flower flies. The adults, although they are true flies, are bee mimics and feed on the nectar and pollen of flowers. They cue in on branches infested with aphids and lay small white eggs individually on the leaves. Once the eggs hatch the maggot-like larvae voraciously search for and consume aphids. It is quite exciting to watch these little guys in action.

Flower or syrphid fly larvae are voracious predators of aphidsPhoto: M. J. Raupp, UMD

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Rose aphid mummy (tan color) with a parasitic wasp in the genera Aphidius developing within itPhoto: M. Raupp, UMD

So the take home message is: Wait! Don’t spray! The natural enemies should come – and they will win over the aphids. Also remember that once the natural enemies consume most of the aphids they will then move onto whatever else may be in the landscapes (ex. scales or spider mites) and provide biological control of other herbivores. Natural enemies will often provide biological control of herbivores if we give them a chance. If here is a need to treat aphids (ex. high amounts of honeydew, high levels of distorted new growth) then use a short residual product such as horticultural oil that will have the least detrimental impact on natural enemy populations. In addition, avoid using high nitrogen or fast release fertilizers. These fertilizers will favor aphids and lead to greater densities of and damage by aphids.

An Aphidius female wasp stinging (inserting an egg) into a live aphidPhoto: Peter Bryant, bugguide.net

Weed of the WeekBy: Chuck Schuster Goutweed, Aegopodium podagraria L. is a plant being found in landscapes now. It will sometimes cause concern with its growing habit of “leaves of three”. Goutweed, also known as Bishop’s-weed and Snow-on-the Mountains, is in the carrot family. Considered a desired plant by some, it is classified by others as an aggressive invasive. It is an aggressive herbaceous plant that has rhizomes which increases the difficulty to control it. The leaves are in groups of three with each having three leaflets, called triternate. The plant can be found variegated and sold in garden centers. The weed form has a lighter green leaf color. White, five-petaled flowers are small in size, and can be found in bloom now and will continue to bloom through mid to late summer. These flowers are found on a leafy stem which can be up to three feet tall. Seeds are similar to carrot seeds and mature in late summer. In understory settings, flowering stems rarely develop. This plant produces a long, white rhizome, which branches often. Goutweed produces a dense cover or canopy which often prevents other vegetation from emerging. In the cultivated form it is often used as a ground cover.

Goutweed has leaves with three leafletsPhoto: Chuck Schuster, UME

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The large, creamy white sweetbay magnolia is fragrantPhoto: Ginny Rosenkranz, UME

Flowering stems can be up to three feet tallPhoto: Cathy Lonas

Goutweed is difficult to control by pulling or other mechanical means. The rhizomes, once broken, will create a new plant. Chemical control in landscape settings is possible using glyphosate products that will translocate into the roots/rhizomes. Use caution when applying near desired plant materials. Covering an area early in the season (mulch or landscape fabric) to prevent photosynthetic action can be a method of control. This method depletes the carbohydrate reserve, thus weakening the plant. It needs to be done early in the season prior to the plant storing reserves for the fall and winter. Use of contact herbicides is ineffective as this plant will leaf out readily after defoliation.

Plant of the WeekBy: Ginny Rosenkranz

Magnolia virginiana, sweetbay magnolia, is a small native tree growing 10-60 feet tall and wide depending on how far south the tree is growing. It grows to about 30 feet tall in Maryland. It is winter hardy from USDA zones 5-9, and the colder the winter the more leaves fall off the tree while in a mild winter the tree will be evergreen. Sweetbay leaves are lustrous leathery dark green above and silvery green underneath, about 3-5 inches long and show off their 2 toned look in every breeze. The extremely fragrant creamy white flowers are 2-3 inches across and bloom from May to September with the majority blooming from May to June. The fragrance has been described as vanilla scented or lemon scented and may be a cross between, but the fragrance is wonderful. The leaves give off a spicy scent when crushed and the roots are also fragrant. The flowers are followed by bright red fruit that ripens in August and is devoured by many native birds. The tree with its smooth gray bark is often multi-trunked and grows best in acidic, wet or even swampy grounds in full sun or even partial shade. In the landscape, sweetbay magnolia fits neatly into small gardens as a specimen tree, as an accent in a rain garden or naturalized in a border or woodland garden. Resistant to magnolia scale, the sweetbay may have problems with leafminer and chlorosis.

MDA Pesticide Container Recycling Program for 2015

For more information:

http://mda.maryland.gov/plants-pests/Documents/Pesticide-Container-Recycling-2015.pdf

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Degree Days (As of June 4)

2015 2014 2013 2015 2014 2013Baltimore, MD (BWI) 844 699 740 Dulles Airport 858 661 782Frostburg, MD 520 368 437 Martinsburg, WV 801 696 706 National Arboretum 1154 970 933 Reagan National 1154 970 933Salisbury 821 862 896 St. Mary’s City 860 764 843

To check degree day (DD) accumulations in your local area go to: http://www.yourweekendview.com/outlook/agriculture/growing-degree-days/. Note: degree days reported in this newsletter use a base

temperature of 50 °F, a start date of January 1st, and the date of monitoring as the end date.

MAC-ISA Arborist Certification CourseAugust 17-19NVCC Loudoun Campus, Sterling VATaught by Joe Murray

Class to prepare for the Arborist exam or get 24 ISA CEUs if already certified.

Topics include all domains of the ISA Arborist Test, such as Tree Biology, Soil Science , Pruning, Plant Health Care, etc. Ability to register 1, 2 or 3 days may be available, contact the office.

For more information or to register visit www.mac-isa.orgQuestions call 703-753-0499.

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

LOCATION

Sambucus nigra Full bloom June 4 (Ellicott City)Stewartia pseudocamellia First bloom June 5 (Ellicott City)

Phenology

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.

Stanton GillExtension Specialist

sgill@umd.edu410-868-9400 (cell)

Paula Shrewsbury Extension Specialistpshrewsb@umd.edu

Ginny RosenkranzExtension Educatorrosnkrnz@umd.edu

Chuck SchusterExtension Educator

cfs@umd.edu

Karen Rane Plant Pathologistrane@umd.edu

Andrew RistveyExtension Specialistaristvey@umd.edu

David ClementPlant Pathologist

clement@umd.edu

Nancy HardingFaculty Research

Assistant

Upcoming Conferences:

Eastern Shore Recertification ConferenceJune 12, 2015Location: Wye Research and Education Center, QueenstownContact: Ginny Rosenrkanz, 410-749-6141http://2015pest.eventbrite.com

MNLGA Nursery Field DayJune 17, 2015Location: Clear Ridge Nursery, Union Bridge, MD

Greenhouse Tour and MNLGA PicnicJune 25, 2015Location: Greenstreet Growers, Lothian, MD

Summer Meeting of the Maryland Christmas Tree AssociationJune 27, 2015Location: Pine Valley Christmas Trees, 342 Blake Road, Elkton, MD 21921 Meeting includes a 60th MCTA Anniversary celebration.For more inforamtion: GaverTreeFarm@aol.com orhttp://www.marylandchristmastrees.org/

Alternative Greenhouse Crops Conference August 5, 2015Location: Brookside Gardens, Wheaton, MD

LCA Hands-on Training SeminarSeptember 16, 2015 Location: Johns Hopkins Univesity, Mongomery County Campus