for Arborists, Landscape Managers & Nursery Managers

Commercial Horticulture May 22, 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- Hollies- Emerald ash borer- Four-lined plant bug- Ambrosia beetles- Potato leafhoppers- Phlox plant bug- Lecanium scale- Maskell scale- Sawflies on roses- Wasps- Fruit insects and diseases

Beneficial of the WeekWeed of the WeekPlant of the WeekPhenologyDegree DaysAnnouncements

IPMnetIntegrated Pest Management for

Commercial Horticulture

extension.umd.edu/ipm

The Weather in Mid-May and Its Impact on PlantsBy: Stanton GillIt may have been a long winter, but from mid-April to mid-May it has been great weather - sunny and dry most of the time which has been ideal for weekend sales at garden centers and for landscape companies installing plant material with no rain delays. Mowing frequency is significantly lower than the 2014 season when we had frequent rains. One impact we are seeing with this stretch of dry weather is that plants that were under root stress or newly transplanted and not being watered frequently are showing scorching of foliage. Some plants are showing tip growth dieback. It has been great to have this dry period, but it is time to end it with some rain. The ground is starting to look rather patched at this point.

Another Weather Update: Early in the week I wrote the article above about the four week drought period and its impact on plant material. Tuesday night, 3- 4 inches of rain came down in central Maryland which was very needed. The earlier comments still stand, even with this rain. We will see the impact of the drought period showing up over the next couple of weeks.

Syrphid flies appeared shortly after the Virginia spiderwort started to flower

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Hollies - Slow to Come BackBy: Stanton Gill, UMEI have been to several sites to look at hollies that suffered significant damage to foliage this last February. Normally, the hollies rapidly grow out of this damage with the spring rains. The dry period for the last four weeks is occurring just as hollies are pushing out new growth. They are still putting out new growth, but it is slower than normal in many landscapes. We have suggested irrigating hollies to help push out the replacement growth this spring until the rains become more regular. The heavy rain earlier this week should help push out new growth.

Emerald Ash BorerBy: Stanton Gill, UMEThe adult emerald ash borer is out and active in most parts of Maryland at this point. The flight of the adult usually starts with the full bloom of black locust. We are just seeing the blooms of black locust fade this week in Washington, Carroll and Frederick counties. The black locusts are in full bloom in Garrett County this week. Paula reported back locust in full bloom in early May in College Park.Control options: Valuable ash trees can be protected with soil, root flair or tree trunk injections of systematic insecticides. We have published a list of chemical control options.

Four Lined Plant Bugs Are Active in MayBy: Stanton Gill, UMETina Graver, Mead Tree Experts, found adults and nymphs of four-lined plant bugs feeding on perennials this week in Potomac, MD and Great Falls, VA. The four-lined plant bug uses its piercing/sucking mouthparts to feed on chlorphyll. It secretes a toxin in its saliva that causes white, dark, or translucent spots on the leaves. If damage is extensive, these spots coalesce and form large blotches. Heavy damage can cause leaves to turn brown and drop.The damage is sometimes mistaken for disease leafspots. They feed on a wide range of annual flowers and herbs, mainly in landscapes and nurseries. I have not seen them damaging plants in greenhouses. There is one generation per year so damage only occurs early in the season.

The four-lined plant bug nymphs are a bright red to orange color with black dots on the abdomen. Later instars have black wing pads running halfway down the abdomen with a yellow stripe on each wing pad; their wings are not fully developed yet. Adults are usually a greenish-yellow color with four black strips running longitudinally down the wings.

Control: Acephate, TriStar. You can try neem products if they are still in the nymph stage.

High populations of four-lined plant bugs can cause a lot of damage early in the seasonPhoto: Tina Graver, Mead Tree Experts

Four-lined bug adults are yellowish green with four black stripes

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Ambrosia BeetlesBy: Stanton Gill, UMEThe rain came down on Tuesday and then the temperatures dropped. The number of adults beetles we picked up in our traps plummeted after Tuesday this week. This is great news after last week’s ridiculously high numbers. It is supposed to warm up in mid-week (May 27 – 29) and I suspect we will see another upswing in adult activity. We will keep you posted on what we find in the trap next week. Meanwhile, the emails continued to flow in reporting damage from ambrosia beetles over the last week, before the cool front blew in.

Mark Selivan, Sav A Tree, is reporting the following:Just wanted to let you know that I have seen some heavy damage on Paper bark Maple from Ambrosia beetle ( holes present as well as frass tubes). Also of note these trees were treated with Astro less than 20 days prior- they broke thru barrier. This property was heavily infested last year and treated. I noted activity on Hornbeam and possibly Beech- I just couldn’t get high enough in canopy to inspect suspect damage. This property is in the Laytonsville area. I also spoke with another tech with a different company (we are all friends of the trees) - he had spotted activity in paperbark and yellow wood in Carroll county- Northern near New Windsor.

These phlox plant bug nymphs are causing distortion on plants and stippling on the foliage

Potato leafhopper feeding causes new growth to curl and harden

Phlox Plant BugWe continue to receive reports of phlox plant bugs activity on plants. Ann English, Rainscapes Coordinator for Montgomery County, is reporting that these bugs are infesting phlox plantings in the county. Look for the yellow stippling and distorted foliage caused by this feeding. The feeding by this plant bug can stunt plants.Control: For control, you can use any systemics (e.g. acephate).

Potato LeafhoppersWe have not been seeing or receiving reports of much potato leafhopper activity so far this season. One grower in central Maryland noted having yellow sticky cards up and only one adult was found on the card on May 20. Today, Marie Rojas, IPM Scout, found a lot of potato leafhoppers on Maple ‘Red Sunset’ in Laytonsville. Look for leafhoppers on plants such as redbud, zelkova, river birch, maple, goldenrain tree, elm, honeylocust, sycamores and London plane trees. Potato leafhoppers are not as likely to be found in high numbers on landscape trees.

Potato leafhopper feeding causes the tip growth on maples to curl over and harden which is typically referred to as ‘hopperburn’. The multi-ple generations keep damaging the new tip growth that flushes out on the maples. The leafhoppers migrate from the south and feed on new growth. When they arrive in an area, females will lay eggs on tip growth and the nymphs will begin feeding a few weeks later.

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Lecanium ScaleBy: Stanton Gill, UMEOn Wednesday night, we (David Clement, Karen Rane, David Driver and I) conducted the Maryland Arborist Association’s evening pest seminar in Owings Mills. Antietam Tree Company brought in a sample of an elm from Washington County that was covered in European lecanium scale. The females are raised up and are in the third instar stage at this point. I flipped over some of the covers and examined the females. Many are gravid (pregnant); some have already laid eggs under the covers. We still have a couple of weeks until crawler activity. The cool spring has put the emergence of many scale crawlers back.

Maskell Scale (Lepidosaphes pallida)By: Nancy Harding, UMDMonitoring Maskell scale on Japanese cryptomeria (Cryptomeria japonica) in College Park found the start of the first generation of crawlers! The accumulated growing degree days as of May 19 in College Park were 448DD. If degree days in your area are near 448DD you should closely monitor plants infested with Maskell scale. If crawlers are active, it is time to treat if populations are high enough to warrant control measures. We will continue to monitor this scale and report when the second generation is active, usually in August.Monitoring: Adult female covers are about 1/16 inch long light brown, narrowly oyster-shell shaped. Male covers are similar but smaller. These scales are hard to see by the unaided eye and tend to congregate in the leaf axils. There are two generations a year in Maryland. Look for yellowing and browning of foliage and dieback of branches. Maskell scale can infest arborvitae, junipers, Leyland cypress, Chamaecyparis, Cryptomeria, spruce and yew.Control: When crawlers are active, apply pyriproxyfen (Distance) or buprofezin (Talus) and 0.5 - 1% oil mixture.

An elm with a heavy infestation of European fruit lecanium scale (left); females covers were flipped over to show that some had eggs like this one (right)

Maskell scale on Cryptomeria japonicaPhoto: Nancy Harding, UMD

Sawflies Active on Roses We are getting in a number of e-mails with pictures of damage on roses, mainly Knockout roses. The roses have holes in the foliage. These holes are being caused by sawfly larvae activity. There are three different species of sawflies we are seeing on roses in May.Control: Conserve (Spinosad) is one of the safer, more effective materials to use.

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Fruit Insects and Diseases By: Stanton Gill, UMEFor those of you taking care of customers with apple, pear, pecan and hardy almond trees, you need to watch out for codling moth. I found adults in traps in Westminster on May 20. Eggs are just starting to be laid near the fruit clusters. This is rather late in the season, but the cool weather has kept their flight activity down until now. Codling moth overwinters as full-grown larvae within thick, silken cocoons under loose scales of bark and in soil or debris around the base of the tree. The larvae pupate inside their cocoons in spring and emerge as adult moths. The moths are active only a few hours before and after sunset. A female deposits 30 to 70 tiny, disc-shaped eggs singly on newly formed fruit, leaves, or spurs. Young larvae seek out and bore into fruit or developing nuts. After completing development they leave the fruit and drop from the trees to find pupation sites in the soil or on debris under the tree; some crawl back up the tree to pupate in bark crevices .

The other pest that is active is the adult of the oriental fruit moth. The adults lay eggs into the new green shoots on peach trees. Later this month and early June, the tip growth will wilt and there will be ooze coming out of the stem. You need to control the first generation now becuase the second generation will bore into the soft fruit later in the season.Control for both insects: At this stage of development, you need to apply either Bt with a spreader sticker or spinosad (Conserve) to the foliage to kill young larvae before they bore into the fruit or nut.

Disease Note: If heavy rain occurs at the end of this week, you should reapply fungicides for disease control.

Beneficial of the WeekBy: Paula Shrewsbury, UMD

Assassin bugs are as deadly as their name indicates! Assassin bugs are true bugs (order Hemiptera, suborder Heteroptera) in the family Reduviidae. There are over 7000 species of assassin bugs making them one of the largest families in the Hemiptera. Assassin bugs range in size from about ¼ - 1.5” depending on species. Most assassin bugs can be recognized by their elongate head and “neck”, long thin antennae and legs, and most importantly both adults and nymphs have a long, dangerous looking proboscis (mouthpart) that they use to suck the life out of their prey - literally. Assassin bugs have a groove on the underside of the thorax. When not using their proboscis, they tuck it under their body and the tip of the proboscis rests in the groove. Assassin bugs are very important predators of a diverse array of pest insects found feeding on ornamental plants and in other natural and managed plant systems. Most assassin bugs are ambush predators and hang out on foliage and flowers in search of prey such as caterpillars, flies, beetles, aphids,

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

WaspsWe have received reports of woodwasp activity from Marty Adams, Bartlett Tree Experts, and Dave Freeman, Oaktree Property Care. The wasps are laying eggs into the trees. Hosts are dead and dying trees.

A woodwasp is inserting an egg into the treePhoto: Marty Adams, Bartlett Tree Experts

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A wheel bug nymph feeding on its newly captured lunchPhoto: P. Shrewsbury, UMD

hoppers, and more. They approach their prey slowly, quickly grab 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. Be careful if you handle these predators – they will defend themselves and their long “beaks” can result in a painful bite. Some species have raptorial legs (similar to praying mantids) or hairs on their legs that help then hold onto their prey. Other species in the nymphal stage will create effective camouflage by covering themselves with the remains of their dead prey.

One of the more common assassins 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) on the adult. 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. 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 (see image) and you should see numerous red and black nymphs on the bark of trees and moving onto the stems and foliage. 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 and knife-like beak they will help keep some of the plant feeding insects from reaching damaging levels. Other common assassin bugs include those in the genera Zelus or Pselliopus (see the images). If you come across one of these assassin bugs watch it carefully and you may see it “assassinate” its lunch.

Adult assassin bug, Psellipus sp. with distinct striping on legs and along the margins of the abdomen Photo: Jon Yuschock, Bugwood.org

The predatory wheel bug adult with its large sucking mouth part stuck into a Japanese beetle resulting in death of the beetlePhoto: Nikolaus Anderson, UMD

Nymph of a green Zelus sp. of assassin bug Photo: Joseph Berger, Bugwood.org

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Weed of the WeekBy: Chuck Schuster The weed of the week that has been generating interest in the last week is Star-of-Bethlehem, Ornithogalum umbellatum. A native of North Africa, Eurasia, it is a weed found in landscape, turf and nursery settings. This plant emerged in many areas as early as mid-April this year and is still blooming in many landscapes and turf settings, and will continue to bloom through early June. It is a perennial, with fleshy grass blade-like leaves. These leaves can grow up to one foot in length with a whitish grooved midrib. The leaves are hollow and are one quarter of an inch wide and up to one foot in length. The root system is bulbous. The plant can reproduce by way of seed to a minimal extent, and by way of bulb division (photo 2) or remaining vegetative structures after attempting mechanical removal. The flower structure is a white, star-shaped, with six petals, each having a distinctive green stripe on the underside. The center of the flower is yellow green. Once it has been mowed it is difficult to distinguish in turf settings. The flowers of this plant are white, on a six to nine inch tall single flower stalk arising from the center. The cluster will produce five to twenty flowers measuring one inch across.

Controlling Star-of-Bethlehem is challenging. Glyphosate products are a very poor control, less than 30% of plants sprayed will be eliminated. 2,4-D products alone can cause an increase in the number of bulbs. Carfentrazone (Quicksilver) has shown good control when applied at the highest label rates at two ounce /acre and repeated three weeks later. It was found to provide greater than 90% control at thirty days post application. Sulfentrazone (Dismiss) is also labeled for this weed. Diquat (Reward) at three week intervals will supply control but damages surrounding plants.

Look for the distinctive green stripe on the underside of star-of-Bethlehem flowersPhoto: Connie Bowers, Garden Makeover Company

Star-of-Bethlehem spreads well by way of bulb divisionPhoto: Chuck Schuster, UME

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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Salvia nemorosa ‘Snow Hill’ is a white flowering sport from ‘Blue Hill’Photo: Ginny Rosenkranz, UME

Degree Days (As of May 21)

2015 2014 2013 2015 2014 2013Baltimore, MD (BWI) 568 439 458 Dulles Airport 585 415 507Frostburg, MD 334 194 269 Martinsburg, WV 553 434 456 National Arboretum 816 656 618 Reagan National 816 656 618Salisbury 560 598 583 St. Mary’s City 572 497 537

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.

Plant of the WeekBy: Ginny RosenkranzMany salvias bloom in the mid spring filling the gardens with vivid blues, lavenders and purples, entertaining the butterflies and humming birds and delighting the gardeners. Salvia nemorosa ‘Snow Hill’ is a pure white flowering sport from ‘Blue Hill’, growing 15-18 inches tall with snowy white flowers climbing up 10 inches of flower spikes. Like all salvias, ‘Snow Hill’ flowers bloom from the bottom up, keeping the garden in color for up to 3 to 4 weeks. ‘Snow Hill’ grows well in average, well drained soils in full sun and USDA hardiness zones 4-9. Once established, ‘Snow Hill’ is drought, heat and humidity tolerant. This compact salvia has light green fragrant foliage that with the pure white flowers creates a spot of cool in the summer landscape. After flowering, the plants should be cut back hard to promote later summer flowering. Listed as resistant to both rabbits and deer, Salvia ‘Snow Hill’ can fit into container gardens, perennial borders, a cottage garden or even in foundation plantings. Salvias are susceptible to powdery mildew, leaf spot and rust while scale and white fly can be occasional insect pests.

Eastern Shore IPM PEST WALK

Who: Stanton Gill, Dr. Dave Clement, Ginny Rosenkranz What: See what Pests are here on the Eastern Shore When: June 3, 2015 starting at 12:00 Noon Where: Wicomico Extension Office, 28647 Old Quantico Road, Salisbury, MD 21801. We will eat lunch and have a brief presentation, then carpool to Salisbury University to walk around and see plant pests in their native environment.

Cost: $25.00

Call: Sign up by June 1, 2015. 410-749-6141 or email: rosnkrnz@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.

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 Pest WalkJune 3, 2015Location: Salisbury, MDContact: Ginny Rosenkranz, 410-749-6141

Procrastinator’s Pesticide Recertification ConferenceJune 5, 2015Location: Montgomery County Extension OfficeContact: Chuck Schuster, 301-590-2807A brochure is on-line

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