for Arborists, Landscape Managers & Nursery Managers

Commercial Horticulture July 14, 2017Coordinator 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

- Pine needle scale- Main peachtree borer- Southern blight- Japanese beetles- Using vinegar as an herbicide- Slug sawfly on oak- Bagworms- Twospotted spider mites- Problems on spruce- Powdery mildew- Dollar spot disease in turf- MDA container recycling- A longhorned borer- Woolly apple aphids

Beneficial of the WeekWeed of the WeekPlant of the WeekPhenologyDegree DaysAnnouncements

Pest Predictive Calendar

IPMnetIntegrated Pest Management for

Commercial Horticulture

extension.umd.edu/ipm

Pine Needle Scale, Chionaspis pinifoliae (armored scale)By: Nancy Harding, UMD

Monitoring pine needle scale on mugo pine (Pinus mugo) in Bowie on July 13, I found second generation crawlers (egg hatch), settled crawlers, and many females still with eggs. The eggs may continue to hatch over a 7-10 day period and will seek feeding sites on the previous year’s foliage. Once they have inserted their mouth parts through a stoma, they remain at the site for the rest of their lives. Settled crawlers are flattened and yellow (see photo). Cast skins are retained and become part of the scale’s wax cover. There are two

Pine needle scale showing crawler (far left arrow) settled crawler (center arrow). Photo below shows an exit hole from a parasitic wasp (arrow)Photos: N. Harding, UMD

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Main Peachtree BorerBy: Stanton Gill

I picked up the first main peachtree borer adult males in my pheromone traps in Westminster last weekend. When adult males are in flight, then they are seeking females to mate with and start a family. Egg laying begins shortly after the moths emerge and lasts only a few days. The eggs are deposited on the trunk at or near the base. Females lay 500-600 eggs on average. The larvae will begin to hatch in 9 to 10 days. Upon hatching, the larvae wander down the trunk to the soil line and burrow into the bark, often entering through a crack or wound.The larvae stages causes serious damage to peach, cherry, plum, nectarine, apricot, and cherry laurel, which seems to be in every commercial landscape anymore.Control: Materials can be applied to kill larvae before they start doing damage in the cambium of the plants. For non-fruit bearing trees a protectant spray of bifenthrin (Onyx) or permethrin is applied to the trunk of the susceptible plant. Do it soon since you want to get them before they enter the cambium. Acelepyrn is a systemic insecticide which has clearwing moth larvae control on the label. I have not tested it out on peachtree borer, but they are a clearwing moth borer.

generations per year. The Degree Days in Bowie on July 12 were 2059 DD. If degree day accumulations in your area are close to 2059 DD, closely monitor plants infested with pine needle scale. If you have active crawlers now is the optimal time to treat. Host Plants: Mugo and Scotch pine are preferred, but other pines and spruce are frequently attacked.Control: Many lady beetles and parasitic wasps feed on this pest; therefore, careful monitoring for predators and parasitoids, as well as using pesticides with little effect on beneficials, can allow biological control to suppress the population. However, if control is warranted, use a summer rate of horticultural oil or an insect growth regulator (IGR) such as Distance or Talus mixed with 0.5 - 1% horticultural oil to target crawlers.

Southern BlightBy: Isadora Gallanar, Extension assistant, and Karen Rane, UMD Plant Diagnostic Lab

The recent hot and humid weather has been great for the development of South-ern blight, a disease caused by the fungus Sclerotium rolfsii. The pathogen has a host range of about 500 plant species. In the landscape, herbaceous perennials such as hosta, coneflower, ajuga and peony are commonly affected. Initial symptoms of the disease are yellowing and wilting of leaves, followed by rotting of the plant at the soil line. Symptoms develop rapidly in high temperatures and especially after rainfall. The fungus produces a white mycelium and round, tan or brown sclerotia that resemble seeds at the base of infected plants. The sclerotia allow the pathogen to survive in the soil for several years, making this disease difficult to control in the landscape. Movement of sclerotia and mycelium on contaminated tools, shoes or plants can spread the disease to new areas. Sanitation (removal of infected plants and surrounding soil) may help reduce disease spread. Fungicides available to home gardeners are not effective in controlling southern blight, but products available to commercial applicators such as azoxystrobin and fludi-oxonil may help manage this disease.

Sclerotia and mycelium of the southern blight fungus on ajugaPhoto credit: Florida Division of Plant Industry, Florida Department of Agriculture and Consumer Services, Bugwood.org

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Active Ingredients Eligible for Minimum Risk Pesticide Use in Nurseries and GreenhousesBy: Stanton Gill

I received an interesting call form a nursery that had a visit from MDA Pesticide Regulation division. The nursery was using off the shelf vinegar (8%) to control weeds. MDA cited the misuse of this material. The nursery manager contacted me with a copy of the 2005 EPA document that listed Active Ingredients Eligible for Minimum Risk Pesticide Products. The EPA listed active ingredients that are exempt and Vinegar was on the list.

I spoke with Ed Crow, who used to be with MDA and is now the pesticide information educator in Pennsylvania, whether this product needed a label or not. Even though it is on the list, a company still has to register it with EPA if it using it as a pesticide. It would need an EPA registration number, directions for use and safety information. A company selling vinegar for food use is one thing, but when you start using it as herbicide, then it does have to be registered with EPA and follow the safety rules and precautions. In the state of Maryland all materials used as pesticide must be registered with the state chemist. You can visit the MDA website for the state chemist and see which materials are registered in Maryland. Our UMD article, Vinegar: An Alternative to Glyphosate has been updated to emphasize the need for registration in the state to use vinegar as a pesticide.

Fleischman Company has labeled a 20% vinegar with an EPA label and a Maryland State Chemist registration and it is sold under the name Vina-Green. The label recommends wearing eye protection and covering the skin since this is an acid. They also have directions for proper use on the label.

Early instar oak slug sawfly larvae feed on the underside of foliage, causing skeletonization damagePhoto: Nancy Woods

Slug Sawfly on OakNancy Woods found oak slug sawflies last week on Quercus lyrata (overcup oak) in Bethesda. Scarlet oak and pin oak are preferred hosts, but they infest other red oaks as well. Look on the foliage for slug sawfly larvae that are slimy, have shorter legs and more than five pairs of prolegs.Control: There are parasites and diseases that help control this pest. Most often control is not necessary, but Conserve would kill the larvae if control is needed.

Japanese Beetle ActivityBy: Stanton Gill

Reports of adult Japanese beetle activity so far are relatively light. We did have a landscaper send in an email with beetles feeding heavily on their customer’s strawberry plants in Frederick County. Grape growers are also reporting a fair amount of adult Japanese beetle activity. An arborist from northern Virginia sent in pictures of adults feeding on his customer’s landscape.

Some wild grape foliage has been eaten by Japanese beetles here at the research center; but overall, populations are low and causing limited damage on plants at this time

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Feeding by bagworm larvae is causing damage on this arborvitaePhoto: Mark Schlossberg, ProLawn Plus, Inc.

BagwormsBagworms are continuing to feed on plants in the landscape this week. Mark Schlossberg, ProLawn Plus, Inc., found them on arborvitae in Perry Hall and noted that there are multiple instars active. Here at the research center, we found a few caterpillars feeding on maple.Control: Options include spinosad (Conserve), Acelepryn, Mainspring, Orthene, and Astro. In light infestations, hand picking off bags is an option.

Multiple wet springs have contributed to the dieback of area spruce treesPhoto: Mark Schlossberg, ProLawn Plus, Inc.

Problems on SpruceMark Schlossberg, ProLawn Plus, Inc., is reporting that many spruce trees in the Baltimore area are showing lower branch dieback. Many have cytospora canker and needle cast. The wet spring this year combined with wet springs for the last three years has taken a toll on these spruce trees.

Twospotted Spider MitesSteve Sullivan, Brighview, is reporting a lot of activity of twospotted spider mites on winged euonymus. He is also seeing the damage show up from spruce spider mites on spruces in the landscape. Spruce spider mite should become active again when the temperature drops in late summer. Look for stippling and bronzing on foliage. Monitor plants for mites by using a clipboard with white paper and tap branches over the paper. Check the undersides of the leaves for the presence of mites and eggs. If left unchecked, mite populations can build up and cause foliage to drop off the plant. Control: Horticultural oil can be used when temperatures go down. Other materials include Abamectin (Avid), Bifenazate (Floramite), Spiromesifen (Judo for nursery use and Forbid for landscape use - both have translaminar action).

Heavy infestations of twospotted spider mites can cause bronzing on foliage

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Dollar spot tends to cause more damage in poorly nourished turfsPhoto: Mark Schlossberg, ProLawn Plus, Inc.

Dollar Spot DiseaseMark Schlossberg, ProLawn Plus, Inc., found dollar spot in turf in Baltimore late last week. Dollar spot generally occurs during periods of warm days and cool nights. It tends to be most damaging in poorly nourished turfs, particularly when soils are dry, when humidity is high or a heavy dew is present. Cultural approaches to minimize injury include avoiding drought stress, controlling thatch and soil compaction, maintaining adequate fertility, returning clippings to lawns, and over seeding with resistant cultivars. Fungicides can also be used to manage this disease.

For more information, see the UMD Fact Sheet on Dollar Spot.

Powdery MildewWe have another report this week of powdery mildew showing up earlier in the season that usual on phlox. High humidity provides a film of water on foliage which creates ideal environmental conditions for powdery mildew infection. Other plants with powdery mildew include dogwood and Monarda. Disease resistant plants are not immune to infection. It is a matter of to what degree a plant is infected when host, pathogen and environmental conditions are present.

Phlox ‘David’s Lavender’ is one of the powdery mildew resistant cultivars

MDA Pesticide Container Recycling ProgramThe 25th year of the pesticide container recycling program will run from June through September. There are 24 collection days at 6 different sites. See the brochure for dates and locations in 2017. Be sure to properly rinse the pesticide containers before taking them for recycling. The Agricultural Container Recycling Council provides a chipper to grind the plastic containers into flakes, which are then transported to a contractor for recycling. For additional information, or to schedule a chipping date at your site, contact Rob Hofstetter, special programs coordinator, Pesticide Regulation Section, Maryland Department of Agriculture, at 410-841-5710.

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Reddish-purplish aphids are underneath the protective waxy covering which can be removed to check for predator activityPhoto: Nick Hoxter, SavATree

Little is known about the hosts of this brightly colored beetlePhoto: Pete Benz

A Longhorned BorerJean Scott sent in a beetle photo that she recieved from Pete Benz in Newtown, PA. This is Cypriacis fasciata (formerly Buprestis rufipes) a type of longhorned borer. Although fairly widespread in the East, little is known of the hosts and life cycle of this beetle.

Woolly Apple AphidsNick Hoxter, SaveATree, found woolly apple aphids on pyracantha this week. Other common hosts include crabapple, alder, elm, mountain ash, hawthorne, and serviceberry. Adults are reddish-purple and have a waxy covering. When monitoring, look for honeydew and sooty mold on trees. This aphid feeds on both roots and on new terminal growth which can cause the leaves to curl and form rosettes. Check to see if the aphids are dead since predators such as lady bird beetles, syrphid fly larvae and lacewing larvae feed on the aphids, leaving the waxy residue behind. There is also a parasitic wasp that feeds on these aphids. If control is warranted, horticultural oil and insecticidal soap can be used which have a reduced impact on beneficial insects if they are present.

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Beneficial of the WeekBy: Paula Shrewsbury, University of Maryland

Earwigs: Are they a beneficial insect or not?

There are many “urban legends” out there including the one that earwigs crawl into your ears at night, and then proceed to the brain where they lay their eggs and feed on your brain. Sounds like a great idea for a sci-fi movie! However, fear not… those of you who have been sleeping with earplugs in your ears can now stop. Earwigs do not crawl into people’s ear or eat their brains. Interestingly, this myth has been around for a long time and is first referenced back in the year 1000. In looking up the etymology of earwig it comes from the old English terms ēare which means “ear” and wicga means “insect” or “beetle”.

Earwigs belong to the order Dermaptera and there are about 2000 species. They are found in most parts of the world. There are 22 known species of earwigs that occur in the U.S. and about one half of those have been introduced (exotic species) accidentally. The most common species we come across in our gardens, landscapes and nurseries (and sometimes as home invaders) is the European earwig (Forficula auricularia) in the family Forficulidae. Earwigs have an elongate shape (~0.5 – 0.75”) and a somewhat flattened bodied (good for getting into cracks and crevices). They are dark brown in color. Earwigs are sometimes called pincer bugs because their most characteristic feature is a pair of cerci at the tip of their abdomen which look like forceps or pincers. Male earwigs have curved pincers, while females have straight ones. These pincers are used for defense and to capture prey, and in some species to assist in copulation. If mishandled, the earwig can give humans a slight pinch. Earwigs will also give off a nasty smelling liquid when they feel threatened. The forewings are thick and somewhat short, and the hind membranous wings are held under the forewings. Although earwigs are capable of flight they seldom are seen flying.

Earwigs are nocturnal and prefer dark, moist, tight places. They are often found in mulch, plant debris, and under logs or bark. Their populations tend to increase during warm, humid periods as we have been having these past few weeks or so. There is one generation per year, eggs are laid in the soil, and there are 5 nymphal instars. Nymphs look like adults only smaller. One of the interesting aspects of earwig biology is that the females provide maternal care. This behavior is somewhat rare in insects that are not social like ants, bees, termites, etc. Earwig mom’s make a small nest (hole or pocket of space) in the soil, usually under a log, rock, or mulch, where she lays her eggs (~20-80). She then keeps her eggs warm, defends them against potential predators, and grooms them to remove fungal spores. Once the eggs hatch the female will feed (regurgitate her food) and continue to protect the nymphs until they molt to second instars, at which point she no longer cares for them. An interesting YouTube showing this can be found at: https://www.youtube.com/watch?v=z-7z9ZGcI8A.

Are earwigs beneficial? Yes they are beneficial, but sometimes they feed on plants and cause defoliation. Earwigs are scavengers and omnivores and consume a wide variety of living and dead material. So they recycle organic matter, eat plant material, and provide biological control by eating other insects and mites. They feed

An adult male European earwig showing characteristic elongate, flat body shape and cerci (pincers)Photo: S. Ellis, Bugwood.org

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Weed of the WeekBy: Chuck Schuster, University of Maryland

False green kyllinga, Kyllinga brevifolia, and green kyllinga, Kyllinga gracillima, are very similar in actual appearance and are often lumped into being the same plant. This is a perennial, sometimes mistaken for yellow nutsedge, but it is part of the nutsedge family. A native of Asia, this plant is found in turf grass and in landscapes. Green and false green kllyinga grow much closer to the ground than yellow nutsedge, will tolerate very close mowing, and survive in poorly drained and frequently wet areas. Kyllinga can be compared to yellow nutsedge and one will notice that the leaf blades are less erect. Kyllinga produces flowers below mowing height <.25 inches on some occasions. The kyllingas can be told apart by the timing of flowering; green kyllinga flowers during all the warm summer months, and false green kyllinga flowers only during late summer. When comparing to other nutsedges, kyllinga has a finer leaf blade, grows much shorter, and does not regrow as quickly (or erectly) as yellow nutsedge after mowing. The inflorescence is much closer to the leaf blade. Green kyllinga is a mat-forming sedge, and has well developed rhizomes that aids its spread. Once large mats are formed, it is extremely difficult to control.

Cultural control will include improvement of drainage at the site. This plant may have become a new issue as the industry has moved away from the use of arsonate post emergent herbicides for crabgrass control to the use of pre-emergent products that have no effect on kyllinga. Chemical control must be done when the plant is actively growing only, and late summer applications are less than successful. Chemical control can include Dismiss (sulfentrazone), (Prosedge, Sedgehammer (Halosulfuron), bentazon (Basagran ) and imazosulfuron , (Celero). Chemical control without improvement of drainage is usually less than successful.

A green kyllinga tuft has about fifty flowersPhoto: Virginia Tech Weed Guide

on mites, aphids, and other insects and their eggs. It is not uncommon to see earwigs feeding on the tender new foliage and flower heads of marigolds, zinnias, and dahlias, in addition to vegetable plants and ripe fruits. Unless populations are extremely abundant this feeding damage usually does not warrant control. If populations are high and damaging the best way to reduce earwig populations is to set out traps in the garden or landscape. If you search the internet for earwig traps you will find guidelines for several types of earwig traps or other mechanical measures to catch earwigs and reduce damage (ex. How to trap Earwigs by Utah State University Extension at https://youtu.be/tlgpfCT0wYo). Placing trap out just before night is optimal since they are nocturnal.

Keep an eye out for earwigs and what they are doing. With the weather we have been having I would predict we might see an increase in their activity.

Plant of the WeekBy: Ginny Rosenkranz, University of Maryland Extension

Hydrangea macrophylla ‘Glowing Embers’, is often called a mophead hydrangea or even a French hydrangea. ‘Glowing Embers’ hydrangea is a compact, deciduous shrub that grows 4-6 feet tall and 6-8 feet wide in a rounded habit. Moist soil important, and the plants may need to be watered more than once a week during periods of extreme heat or drought. All flowering shrubs need sunshine to bloom, but the mophead hydrangea prefers morning sunshine and afternoon shade to prevent wilting, and daily watering if planted in full sun. The soil should be rich in organic matter and have a slightly acid to neutral pH (6.0-6.5) for best desired red flower color, and a light addition of mulch to maintain soil moisture. A soil test will show if an addition of lime is needed to heighten the deep red coloring. ‘Glowing Embers’ blooms on the last summer’s growth, so light

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pruning to shape up the plants should be done right after the early summer flowers so the late summer flowers can bloom on the early spring growth. The plants are winter hardy from USDA zone 6-9, but sometimes extreme sudden cold can damage dormant flower buds. The huge 8-inch flower cluster is filled with sterile blooms which start out soft green or white but mature to a vibrant pink, then rose, and then a deep burgundy red. The flowers bloom for a very long time and even when they dry up they add decoration to the plant. The large 4- to 8-inch leaves are a dark glossy green and are held on stems in an alternate fashion and are the reason for another nick name of big leaf hydrangea. Pests include bud blight, bacterial wilt, leaf spot, powdery mildew and occasionally aphids. Flowers of Hydrangea ‘Glowing Embers’ have a long bloom

timePhoto: Ginny Rosenkranz, UME

Degree Days (As of July 12)Annapolis Naval Academy (KNAK) 2033 Baltimore, MD (KBWI) 1899 College Park (KCGS) 1870 Dulles Airport (KIAD) 1927Ellicott City (E247) 1832 Fairfax, VA (D4092) 2087Frederick (KFDK) 1874 Greater Cumberland Reg (KCBE) 1765 Gaithersburg (KGAI) 1811 Martinsburg, WV (C1672) 1751Natl Arboretum.Reagan Natl (KDCA) 2303 Rockville (C2057) 2137 Salisbury/Ocean City (KSBY) 1943 St. Mary’s City (St. Inigoes, MD-KNUI) 2141 Westminster (KDMW) 2000

Important Note: We are now using the Online Phenology and Degree-Day Models site.

Use the following information to calculate GDD for your site: Select your location from the mapModel Category: All models Select Degree-day calculatorThresholds in: Fahrenheit F Lower: 50 Upper: 95Calculation type: simple average/growing dds Start: Jan 1

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

Commercial Horticulture Conferences

PGMS Green Industry Field Day July 20, 2017 American University, Washington DC

Green Industry Summer PicnicAugust 19, 2017Location: Just This Side of Paradise Farm, Woodbine, MD

Cut Flower Tour - Eastern ShoreSeptember 12, 2017

Top Native Plants for the Mid-Atlantic RegionPresenter: Holly ShimizuOctober 11, 2017Location: Johns Hopkisn University, Rockville, MDRegistration Information