for Arborists, Landscape Managers & Nursery Managers

Commercial Horticulture June 10, 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- Japanese maple scale- Emerald ash borer- Bagworms- Problem on conifers (herbicide damage)- Fall webworm- Indian Wax Scale- Brown marmorated stink bug- Peachtree borers- “Popcorn” disease on mulberry- Flea beetles- Chrysanthemum lace bug- Black locust leafminer- Fireblight

Beneficial of the WeekWeed of the WeekPlant of the WeekPhenologyDegree daysConferences

Integrated Pest Management for

Commercial Horticulture

www.ipmnet.umd.edu

The WeatherIt was great weather this weekend, but now I am hearing it is just too dry. Earlier it was too wet. In New Hampshire they had 57 days of cloud cover and wet weather and now it is sunny. At least people were buying last weekend with the sunshine and nice temperatures. Anyway, it is ok to wish for a little rain – we could use it about now.

Japanese Maple Scale Crawler UpdateIn College Park we are at 1138 degree days (DD) as of Thursday June 9th. The Japanese maple scale (JMS) population on red maple consists of many settled crawlers, and still a number of females with eggs. This should be an optimal time / activity level to apply control for JMS using insect growth regulators such as Distance or Talus (with a 0.5% horticultural oil) if you are in College Park or at similar DD / JMS crawler activity levels. See the IPM Report from May 27th for more detail on JMS activity, DD, and management.

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Epicormic growth on trunk and at base of tree

Emerald Ash Borer in Howard CountyCongratulations to Eagle Eye Rich Godwin of Mead Tree and Turf Company

First off, our hands-on training sessions on Invasive Species we (University of Maryland Extension and MDA) have been conducting has shown its worth again. A couple of years ago one of the arborists attending the Invasive Species training called in with the first find of EAB in Northern Virginia. It was later confirmed by VA Department of Agriculture.

Now, one of the people that graduated from our two-day training, Rich Godwin of Mead Tree and Turf of Woodbine, MD has found EAB in a new area. Rich Goodwin was in the invasive species training session two years ago and received his NPDN training certificate. Rich called me (Stanton) in the late afternoon earlier this week to report that a new customer had called him out for a tree consultation. He examined two ash trees at a site in Howard County. He called me on Monday afternoon to report there were D-shaped holes and epicormic growth on the trees. I told him to send me digital photos, which he did. They looked like EAB exit holes. Even though it was late in the day I decided it was worth visiting the site and arrived around 6:30 p.m.

When I walked over to the trees there was an adult sitting on the rough bark. The owner’s son ran and got me a container and I captured a couple of adults. The interesting thing is the adults would take flight but only went short distances to move to the other positions on the trunk. There was a fair amount of adult activity on the trunks and several were out of reach without the aid of a ladder.

I drove these back to the CMREC lab and examined them under the dissecting scope and compared them to mounted specimens. I was 99 % sure they were EAB in the field, but the dissecting scope examination confirmed this ID. I returned to the site with a chisel, hammer and an awl. I asked the couple for permission to chisel into the bark. The owners said the tree had dieback last year, but they felt it was just starting at this point. They noted that this year it was more pronounced which is why they called an arborist. It looks like the tree has been infested for at least 2 years, probably 3 or 4 is more likely. I examined another ash in the backyard and it had dieback in the upper canopy and we found a couple of exit holes. We examined trees in the neighborhood and found two additional lots with infestations that are light at this point, but still present.

Adult emerald ash borers showing color variation

Mines made by emerald ash borer larvae

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BagwormWe received the first report of bagworm hatch on June 7 for Adamstown (Frederick County). Mark Schlossberg, ProLawn Plus, Inc., reported bagworms in Reisterstown on June 9 on a Colorodo blue spruce.Control: At this early stage, Bt is still a good option. Conserve, Orthene, Acelpryn, and Astro all provide good control of bagworms.

Small bagworms on sprucePhoto: Mark Schlossberg, ProLawn Plus, Inc.

Examples of damage being found on conifers in the landscapePhotos: Mark Schlossberg (top left), Barb Neal (top right) and Gary Crutchfield (bottom right)

Problem on Conifers: Possible herbicide damageWe are getting a lot of pictures sent in with herbicide damage on white pine and spruce in areas near where the herbicide Imprelis has been used. The potassium salt of aminocyclopyrrachlor (Imprelis) appears to be carried into roots of conifers and causing damage. If you suspect damage let us know at sgill@umd.edu. Also, you can contact your local DuPont representative if you believe you are getting damage from Imprelis. Since this is a new class of chemistry, most testing labs are not equipped to test foliage for the presence of Imprelis. We are searching for labs that can run tests for this material.

Steve Williams sent an email and mentioned that he found that watering the client’s trees that had damage was helping to keep foliage green and slowing down the damage. This might be worth trying.

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Fall WebwormKevin Nickle, ProLawn Plus, Inc., brought in a sample of crabapple with an infestation of the first generation of fall webworm. Early instar larvae were feeding within the webs they made. Damian Varga, Scientfic Plant Servies, also reported activity on river birch in Catonsville on June 6. Fall webworm has a wide woody plant host range. They feed within the webbing which is around the tips of branches and not in the crotches like Eastern tent caterpillars which are active much earlier in the season.Control: Bt for early instars or prune out webbed branches.

Brown Marmorated Stink Bug (BMSB) TrapsThanks to tall of you who sent in e-mails commenting on the inexpensive bottle/light trap for BMSB. Many people had suggestions on how to improve the traps. We tried out several of the suggestions and no surprise- none of them really improved the trap. We even tried the suggestion to coat the trap with Pam on the inside of the funnel. The BMSB still clung to the surface of the plastic and remained in the funnel area of the trap, not in the chamber. Don’t worry, we have not given up and continue to try different modifications to see if we can get one to work. I spoke with Margaret Baynes in Oregon this week. She said they have had the BMSB for 3 years, but currently not in the Corvallis area of Oregon where she resides. It is still just a nuisance and has not increased to plant damaging levels yet. She mentioned that the spotted winged drosophila was growing into a major pest in their state. This pest needs a wound in the vegetable or fruit to start feeding. Now with the combination of BMSB and spotted winged drosophila, the stink bug may be able to make the initial wound with the fruit fly following up. This is a bad combo and let’s hope this spotted winged drosophila does not make it to this coast.

Indian Wax ScaleIndian wax scale, Ceroplastes indica, is in the crawler stage this week. Damian Varga, Plant Scientific Servies, found crawlers on maple in Catonsville on June 6. Crawlers settle on twigs and stems, not on foliage. This scale feeds on over 50 species of landscape plants, but is commonly found on hollies (especially ink berry and deciduous hollies), camellia, pyracantha, and barberry.Control: Horticultural oil does not work well on this scale. Distance applied when crawlers are present works well. Imidacloprid can also be applied as a soil drench in April. It takes 30 - 60 days for uptake into the stems of the plant. Soil application of dinotefuran (Safari) is uptaken in 2 – 3 weeks and should give good control.

Peachtree BorersPeachtree borers continue to be active this week. Marty Adams, Bartlett Tree Experts, brought in a pheromone trap that was set out in Finksburg that attracted plenty of the borers in just two days.

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Flea beetle and damage on hibiscus

Fungal Disease on White MulberryBryan Lilly, Natural Elements LLC in VA, sent an email with an interesting disease problem. He has a customer who actually WANTS a white mulberry tree! Although this is an invasive species, the fruit are consumed by a number of bird species, so bird-lovers may want to keep them. The tree in question developed a disease of the fruit called popcorn disease. Individual carpels in the fruit become swollen, dry and white in color. They resemble unpopped kernels of popcorn, hence the name “popcorn disease”. The disease is caused by a fungus, Ciboria carunculoides, which survives the winter as sclerotia (dark, hard resting structures) in fallen infected fruit. In the spring, when mulberries are flowering, the sclerotia produce cup-like apothecia from which spores are released into the air to infect developing fruit. Symptoms develop in May and June as the fruit matures. Infected fruit drop from the tree and serve as the source of spores next season. Removing and destroying infected fruit will help reduce the amount of inoculum and help to reduce the disease (a difficult task, though).

Here are two links with photos and information:http://www.apsnet.org/publications/imageresources/Pages/Iw000018.aspxhttp://aggie-horticulture.tamu.edu/galveston/Gardening-Handbook/PDF-files/GH-067--popcorn-disease-on-mulberry.pdf

Flea BeetlesFlea beetles are active this week, feeding on hibiscus in Ellicott City. Look for adults feeding on the topside of the foliage. With large rear legs, these beetles can jump when disturbed. Flea beetles are commonly found on many vegetable crops.Control: Usually not necessary. Mature plants should recover from damage and control is not usually warranted. Applications of Azatin can be used to reduce flea beetle populations.

Popcorn disease on mulberryPhoto: Bryan Lilly, Natural Elements, LLC

Chrysanthemum Lace Bug, Corythuca marmorata, on AsterThis week in College Park asters had high populations of chrysanthemum lace bug and damage. Obviously these insects had been busy feeding for awhile. The chrysanthemum lace bug feeds on a wide range of herbaceous perennials in the Asteraceae or Compositae family such as asters, sunflowers, black-eyed susans, goldenrods, and more. Adults are about ¼”, with lace-like wings held flat over their bodies, with light brown markings. Nymphs are a golden brown in color. Chrysanthemum lace bug overwinters as adults and begins laying eggs in early spring. By late May or so first generation eggs are hatching, and adults are abundant by June. There were mostly adults in the College Park infestation. Chrysanthemum lace bug is reported to have two generations in CT, so likely at least two in MD. They will be active throughout the season into September. Monitoring and Damage: Interestingly, chrysanthemum lace bug feed on the upper and lower leaf surface of their hosts and cause typical lace bug damage. This damage includes: yellow stippling of foliage that can progress to leaf browning and plant death; and black frass droplets on upper and lower leaf surfaces; eggs inserted into the leaf (mainly along major veins) and covered with frass droplets. If you have chrysanthemum lace bug this year, next spring (late May) monitor for stippling damage, eggs, and newly hatched nymphs. This is the optimal time to target controls.Management: At this time populations are high and damaging. An application of horticultural oil or insecticidal soap should knock back the population, but remember to get good coverage on upper and lower leaf

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surfaces. Systemics such as acephate or imidacloprid have also been shown to work. Imidacloprid will likely take a little time to start killing the lace bugs, but should provide long-term control.

For more detailed information on chrysanthemum lace bug life cycle and management go to:http://greenindustry.uwex.edu/problemdetails.cfm?problemid=1400 http://www.ct.gov/caes/cwp/view.asp?a=2823&q=377626

Aster showing yellowed foliage with black frass spots and chrysanthemum lace bug adults. Photo: Paula Shrewsbury, UMD

Chrysanthemum lace bug adults showing lace-like wings and light brown color patterns. Photo: Paula Shrewsbury, UMD

Black Locust LeafminerAdults and larvae are actively feeding this week on black locusts in the landscape. Look for skeletonization and shothole damage on foliage from the adults feeding on the foliage of black locust trees and sometimes yellowwood. It is the larvae that, as populations increase throughout the summer, cause the irregular blotch mines that start white and eventually turn brown. Some mistake this summer damage as caused by pollution, but it is caused by this beetle. There are two generations of this beetle in Maryland. Black locust is a native, sometimes invasive, tree that often leafs out again later in the season.Control: Not necessary.

Adult black locust leafminer (top) and adult and larval feeding damage on black locust foliage (bottom)

FireblightWe continue to receive reports of fireblight on trees in the landscape. Kevin Nickle, ProLawn Plus,Inc., brought in a sample of crabapple infected with fireblight.

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Beneficial of the Week, Paula ShrewsburyPupal stages of natural enemies are sometimes strange looking things

Along with the chrysanthemum lace bug attacking asters in College Park were aphids feeding on the plant and also a suite of natural enemies. These included lady beetles, syrphid (flower) flies, and lacewings. What was cool this week was the presence of lady beetle pupae and syrphid fly pupae. This is the stage of holometabolous insects where they transform from the immature to the adult stage. Lady beetles pupate on the foliage, syrphid flies may pupate on the foliage or the soil. Many people are not familiar with these stages because they are less commonly observed. See the images below to help recognize the different life stages of these beneficial insects.

The larval stage of a syrphid fly consuming aphids. Photo: Mike Raupp, UMD

Syrphid (flower) fly pupa on the leave of aster. Note the aphid in the lower right for relative size. Photo: Paula Shrewsbury, UMD

Beneficials in the Landscape

Craig Greco, Yardbirds, Inc., sent us a photo of a wasp going after fall webworms on a mulberry tree Photo: Craig Greco, Yardbirds, Inc.

Praying mantids are being found on various plants here at the research center in Ellicott City

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Two different views of the pupal stage of the native convergent lady beetle. Photo: Paula Shrewsbury, UMD

An adult convergent lady beetle. Note the two white lines on the black pronotum (just behind head) converging towards each other.Photo: Paula Shrewsbury, UMD

Weed of the Week, Chuck SchusterProstrate knotweed, Polygonum aviculare, is a summer annual that has a prostrate growth habit. It is found in turf and some landscape settings throughout the United States. The leaves are alternate on the stem, with a lanceolate outline. Leaves occur on a short petiole and have a thin sheath called an ocrea that encircles the stem at the leaf base. Leaves are one half to one and one quarter inch long and up to one quarter inch in width. Stems will grow up to twenty inches in length. Prostrate knotweed prefers compact soils that will include many high traffic areas and some athletic fields and lawns. Prostrate knotweed has a taproot, produces a flower that is white to pinkish white in color that occur in clusters of one to five flowers and a dark reddish brown fruit.

To control this weed remember the importance of reducing compaction when possible. Prodiamine (Barricade) is a pre-emergent that can be used in landscape and turf. Isoxaben and Trifluralin (Snapshot) in a granular form is often used in landscapes and nurseries. Most 2 4D and dicamba mixes will also control this weed very well.

Prostrate knotweedPhoto: Virginia Weed ID Guide

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Plant of the Week, Ginny RosenkranzPrickly pear cactus (Opuntia compressa) is a native herbaceous perennial that has large fleshy pads that can, from a distance, look like leaves. They are modified stems that act as both a water holding vessel and a source for photosynthesis, like a modified leaf. It is also the site for flower and fruit production. It defends itself from thirsty animals by growing large spines that are the true modified leaves. There is usually another cluster of smaller spiny thorns called glochids just above the larger thorns that are yellow or red and can easily detach from the plants. Unfortunately they are often detached into the hands of the landscaper, making gloves a necessity. The flowers of prickly pear cactus are bright yellow, 3-4 inches across and quickly turn into an edible fruit that can be found in stores under the name of ‘Tuna’. There can be as many as 8-16 flowers on each pad. The plants grow 6-18 inches tall, with the pads growing from 4-16 inches tall and up to 9 inches wide. In the landscape prickly pear cactus can be used as a border plant, one that declares ‘mind your step!’ The plants grow in full sun in many soil types but do best in very well drained soils. Once established, the plants are very drought tolerant. In the northern areas, the plants should be protected from the winter winds. Prickly pear cactus is hardy in USDA zones 4 -10. Poorly drained soils, frost and sunburn are among the abiotic pest problems while phyllosticta fungus causes black lesions on the pads and the Sammon’s virus causes white rings or a mosaic pattern on the pads. Cochineal scale is the usual insect pest on prickly pear cactus. This scale was prized for the bright red dye it produced when the scale was crushed and it is still used to make natural food coloring.

Yellow cactus flowerPhoto: Ginny Rosenkranz

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

LOCATION

Cornus racemosa Full bloom (June 9) Silver RunIlex verticillata Full bloom (June 9) Silver RunRhododendron ‘Millenium’ First bloom (June 9) Silver RunSpigelia marilandica Full bloom (June 9) Silver RunStewartia pseudocamellia First bloom (June 9)

First bloom (June 6)Silver RunEllicott City

Thermopsis caroliniana Full bloom (June 9) Silver RunViburnum nudum ‘Winterthur’ and‘Count Pulaski’

Full bloom (June 9) Silver Run

Yucca filamentosa ‘Color Guard’ First bloom (June 9) Ellicott CityYucca smalliana ‘Bright Edge’ First bloom (June 9) Ellicott CityYucca pallida Full bloom (June 9) Ellicott CityZenobia pulverulenta ‘Woodlanders Blue’

Full bloom (June 9) Silver Run

Degree Days (As of June 9)

Baltimore, MD (BWI) 1095 Dulles Airport 1049 Frostburg, MD 615 Martinsburg, WV 948 National Arboretum 1208 Reagan National 1198 Salisbury 1122

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 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