for Arborists, Landscape Managers & Nursery Managers

Commercial Horticulture September 29, 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

- Boxwood blight alert- Banded ash clearwing borer- Leaf drop on hemlocks- Brown marmorated stink bugs- Green stink bugs- Scentless plant bugs- Grubs- Impatiens downy mildew- Allium leafminer- Problems with slugs- White prunicola scale- Indian wax scale- Locust borer- Crapemyrtle aphids- Saddleback caterpillar- Praying mantids

Beneficial of the WeekWeed of the WeekPlant of the WeekDegree DaysAnnouncements

Pest Predictive Calendar

IPMnetIntegrated Pest Management for

Commercial Horticulture

extension.umd.edu/ipm

Alert for Landscapers - Boxwood Blight By Adria Bordas, Virginia Cooperative Extension, Fairfax County, and Karen Rane, UMD Plant Diagnostic Lab

Over the past several weeks, we have noticed an increased number of positive Boxwood Blight samples coming into our labs from landscapes in Virginia, Maryland, and DC. Landscapers and property owners need to be on the lookout for symptoms of boxwood blight. Initial symptoms include dark leaf spots, dark streaks/lesions on green stems, and leaf drop (usually beginning on lower leaves, see photos). Common landscape maintenance activities, such

Boxwood blight leaf lesionsPhoto: David Clement, UME-HGIC

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as pruning, shearing and cleanup of fallen leaves, have the potential to spread this disease within a landscape or between landscapes. There have been a few instances locally to our region where the disease may have been introduced to properties through these landscape maintenance activities. Spores and fallen diseased leaves can be moved on tools, boots, tarps, hoses, and vehicles. You can be proactive and aware by walking any work site first to see if there are boxwoods on the property and seeing if there are problems before the work crew goes onto the site. Make sure you are prepared: Pack and bring along a cleaning kit to clean your tools. Lysol disinfectant concentrate (higher concentrated dilution) or 10% household bleach solution with contact on contaminated material for a minimum of 5 minutes. If a client’s boxwoods have been confirmed to have boxwood blight, schedule work on that property at the end of the day and sanitize tools and equipment before using them again. Take time now to look at the Virginia Boxwood Blight Taskforce Website. There are many images showing symptoms and signs of the disease, treatment lists, sanitizers and other resources: https://ext.vt.edu/agriculture/commercial-horticulture/boxwood-blight.html.

Dark stem lesions caused by boxwood blightPhoto: Karen Rane, UME

Boxwood blight in the landscape. Note defoliated shrub (back left), and brown foliage with numerous fallen leaves below boxwood (right fore-ground). Photo: Adria Bordas, Virginia Cooperative Extension, Fairfax County

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Brown marmorated stink bugs get into buildings and homes through cracks around doors and windows

Banded Ash ClearwingBy: Stanton Gill

Since emerald ash borer moved in and is devastating green and white ash, there has been less concern about activity from the banded ash clearwing borer. Just so you know, we have been picking up flight activity of this moth for the last 2 weeks. Adult females started laying eggs on white and green ash in central Maryland in late September.

If you treated your customers’ ash trees for emerald ash borer using emamectin benzoate (TriAge), it should give 2 years of control of EAB and as a side effect also control banded ash clearwing borer. Two for one.

Brown Marmorated Stink BugsWe are starting to see some activity of brown marmorated stink bugs, but have not had reports of high numbers this year. There might be localized high populations. Marie Rojas, IPM Scout, started seeing them on September clustering on the outside walls of her farmhouse in Montgomery County.

Heavy Leaf Drop on HemlocksBy: Stanton Gill

Paul Wolfe, Integrated Plant Care, called to report that a very heavy needle discoloration of hemlocks is occurring in Bethesda, Chevy Chase, and Potomac this week. Paul said his phone is ringing off the hook with customers wanting to know what is going on with the trees. Most evergreens retain their foliage for 2 to 3 years. When this yellowing of old foliage occurs, it looks like the tree is yellowing all over and dying – at least to most customers. This is just a fall color thing. When white pines were popular back in the last century it was very common to see the old needles turn in October every 3 years. Not to worry – it is fall color, so enjoy it.

Dave Clement, UME-HGIC, has done a video explaining normal fall color in evergreens. It is posted at https://www.youtube.com/watch?v=6MZrVEQX3Xs&list=PL8OwpJmur8rsLgGLbKyTeY0H0YaDiLMGc&index=2

After banded clearwing borer moths emerge, the pupal case remains on the trunk

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Scentless plant bug nymphs have been feeding over the last two weeks on hibiscus seed heads

Trichopoda pennipes is a species of tachinid fly that parasitizes plant bugs

Scentless Plant BugsScentless plant bug nymphs (Niesthrea louisianica) are feeding on Hibiscus moscheutos seed heads now. This native bug feeds on plants in the mallow family. This year is the first time that they have been spotted in high numbers on plants at the research center. They also feed on seeds of velvetleaf which is a weed in the mallow family that is a problem in many crops. This plant bug significantly reduces seed production.

Green Stink BugsThere has been an increase in green stink bugs around the research center this month. As ornamental plants produce seed this time of year, there is plenty of food for these stink bugs which primarily feed on developing seeds and fruit. Nymphs are feeding on perennial hibiscus seed heads here at the research center. They have piercing and sucking mouthparts which they insert into seeds and fruit to feed. They liquefy the plant’s contents that they then suck out with their straw-like mouthpart. A variety of predators and parasitoids feed on them including the tachinid fly (Trichopoda).

Note the white tachinid fly egg on this green stink bug nymph

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Grubs?Connie Bowers, Garden Makeover Company, sent an email asking if we are getting reports of unusually high numbers of grubs this year, which she is noticing. Let Stanton know what you are seeing this year at sgill@umd.edu.

White Prunicola ScaleKevin Nickle, ProLawn Plus, Inc., is reporting the heaviest white prunicola scale populations that he has seen in years. This scale is commonly found on Prunus species and also seen on magnolia, ligustrum, rhododendron, forsythia, boxwood, and lilac. Check to see if third generation crawlers are present.Control: Talus or Distance can be used.

Connie found a group of about a dozen grubs in the soil not even near turfgrass, under some decaying wood Photo: Connie Bowers, Garden Makeover Company

Impatiens Downy Mildew By: Dave Clement, UME-HGIC

I just noticed this white coating on my regular garden impatiens this past weekend. It’s caused by the impatiens downy mildew disease that is wide spread across Maryland this year. Check the lower leaf surfaces of your impatiens plants. There are no curative controls for this disease so replacement with non susceptible plants is the best option.

Fewer garden impatiens are being grown in the area since impatiens downy mildew was found infecting plants in Maryland in 2012Photo: David Clement, UME-HGIC

This one branch is completely covered with white prunicola scalePhoto: Kevin Nickle, ProLawn Plus, Inc.

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Allium Leafminer: Possible Ornamental Plant Pest?Jerry Brust, UME

There is a new pest in our area first found in Lancaster Co. PA in December 2015. It is the Allium leafminer (Phytomyza gymnostoma Loew) which attacks Allium plant species. Leeks tend to be the most damaged host, but all allium species may be attacked. Adult females have yellow/orange heads and yellow ‘knees’ (fig 1) and make repeated punctures in a leaf with their ovipositor. These punctures are organized in a straight line going down the leaf from the tip (fig 2). Damaged leaves can appear wavy, curled or distorted. Larvae mine leaves, and move into bulbs and leaf sheathes where they pupate. Both the leaf punctures and mines serve as entry routes for bacterial and fungal infections. High rates of infestation have been reported from some allium fields in Pennsylvania. The reason I am telling you this is because we do not know if this pest will attack Allium plant species in the landscape. Not only would this cause possible landscape plant loss, but these infestations would also act as a breeding area for the pest to build its population early in the spring and later in the fall; the two times of year when it is most active. If you see any similar damage to allium species or the fly itself on landscape plants please let me or Stanton know.

Fig. 1 Adult female Allium leafminerPhoto: E. Agallou and D. Collins

Fig. 2 Ovipositor/feeding damage to onion transplants by Allium leafminerPhoto: Sarah May

Problems With SlugsJerry Brust, UME

Over the last 2-3 weeks, I have noticed the mums that were planted in my yard seemed to be going downhill rather quickly. The flowers looked beat-up and brown after only a week of being placed in the landscape (fig 1). One night when I was out looking at the garden I noticed many brown things on the flower heads. To my dismay they were slugs, lots of them. This surprised me as I did not see feeding holes in the foliage of the mums, just ugly decaying flowers (fig 1). Large ragged holes in the foliage are the type of feeding damage I expect from slugs (fig 2). Slugs can feed on a wide variety of plant material and can be especially troublesome on hostas, violets, ageratum, lilies, cleome, mums, strawberries, lettuce, and cabbage. Slugs are a type of mollusk, related to clams and oysters. They are soft bodied, generally brownish or gray, with eye stalks (fig 3). They vary in size

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from 1/4 inch to two inches or longer. There are a great number of slug species, but only a few pose real problems. Some of these are the gray garden slug, Deroceras reticulatum, the tawny garden slug, Limax flavus, the spotted garden slug, Limax maximus, and the brown garden snail, Helix aspersa. Most of the slugs in my landscape were gray garden slugs.

Slugs are hermaphroditic (both male and female organs occur on each slug), but they must cross fertilize to produce viable eggs. Eggs (150-300 total) are laid in small clusters of about 25, about an inch deep in damp, loose soil or debris, during the wetter months of spring and fall. Egg hatch occurs in 30 days when the soil is damp; if it is too hot and dry development is suspended. Adult size is reached in only 4-10 months and slugs can live for several years. While they are capable as a group of overwintering in all stages of development, they overwinter in our area primarily as adults or eggs. They survive inhospitable environments by burrowing into the soil, sometimes as deep as 3 feet.

Slugs dehydrate easily and need adequate moisture levels to survive. They absorb water directly through their skin and drink from water sources. During the day, they hide in cool, damp locations under leaves, rocks, wood chip mulches, stepping stones, porches, or flower pots. Large populations can sometimes be found hiding in groundcovers such as vinca and pachysandra. They go back to their favorite hiding and feeding places night after night unless disturbed or the site becomes dry. Slugs avoid crossing dusty or dry materials. As most everyone knows the shiny dried slime trails slugs leave behind on plants or along the ground as they move are good indicators of their activity.

ManagementNatural enemies of slugs include rats and mice (although I suggest you do not augment their numbers), toads, some ground beetles and their larvae. One of the least expensive, and most effective, but not very practical control for slugs is hand picking. Take a bucket of soapy water and a flashlight to the garden at night and pick the slugs from the leaves and flowers of the chrysanthemums and other plants and drop them in the bucket (this is what I did for a couple of nights). Regular hand-picking significantly reduces populations without adding chemicals to the environment. Drying out wet areas and eliminating hiding spots created by debris, old wood, or organic waste will create an unfavorable habitat for the slugs. Adding copper strips around small beds or favored plants, such as chrysanthemums, stops slugs from feeding because the copper reacts with their bodies.Chemicals: There are several pesticides that are useful for slug control. Iron phosphate (i.e., Escar-Go, Sluggo),

Fig. 1 Tale of two mums bought at the same time and at the same developmental stage. Good looking mum on left with no slug feeding; one on the right with lots of slug feeding.Photo: Jerry Brust, UME

Fig. 2 Slug feeding on hostaPhoto: Jerry Brust, UME

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applied to the soil as granules, is a less toxic bait for slugs. It is mixed with a food product that draws slugs to the bait. Once slugs consume the bait, they stop feeding and die in 3-6 days, which is why you may continue to see slugs moving around in the garden after the bait is put out. Some of the chemical slug baits contain metaldehyde (e.g. Deadline, Defender), available as a granular or liquid paste. When metaldehyde is eaten by slugs, it destroys their ability to move and digest food. Apply it to the soil near slug-infested plants. Metaldehyde is more effective during warm, dry weather (like now). Baits containing metaldehyde can be poisonous to other animals and humans. If you have children or dogs, it may be best to choose baits that contain iron phosphate instead. Iron phosphate is almost as effective as metaldehyde, but is only toxic to mollusks. Copper compounds (copper silicate and copper sulfate) are good repellents. They are usually mixed with water, and then sprayed on plants. Copper products repel slugs but usually do not kill them. Do not spray copper compounds near baits; slugs will avoid baits mixed with them.

Fig. 3 Two slugs feeding on chrysanthemumPhoto: Jerry Brust, UME

Indian Wax ScaleJohn Ford, Chapel Valley Landscape, found a little Indian wax scale on cherry laurels in Fairfax, VA on September 26. This soft scale also feeds on hollies, azaleas, pyracantha, euonymus, boxwood, flowering quince, camellia, pear, azalea, persimmon, plum, barberry, and magnolia. Crawlers are active in June in Maryland. Females overwinter on the stems. Heavy infestations can cause plant dieback. Control: Horticultural oil does not work well on this scale. Pyriproxyfen (Distance) or buprofezin (Talus) applied when crawlers are present works well. Another option is to use a soil injection, basal flare, or soil drench of a systemic insecticide, dinotefuran (Safari, Transtect).

Indian wax scale overwinters as adult females on the stemsPhoto: John Ford, Chapel Valley Landscape

Locust BorerNow is the time of year that locust borer adults are spotted at flowers, especially goldenrod blooms. Females are laying eggs at this time of year in bark crevices. The larvae hatch in fall and begin to feed. They move into the heartwood in spring. The larvae of this native beetle feed only on black locust (Robinia pseudoacacia). There is one generation per year. Diversity of tree species in an area and adequate moisture help to reduce damage from this beetle

Black locust borer adults are often spotted at flowers at this time of year

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Crapemyrtle AphidsMark Schlossberg, ProLawn Plus, Inc., found sooty mold on crape myrtles from an infestation of crapemyrtle aphid this week in Owings Mills. The aphids had produced a lot of honeydew on which the sooty mold was able to grow. It is a small yellowish-green aphid with black spots. There is a hair coming out of each of these spots.Control: It is very late in the year for making any applications for control. Treatments will only reduce the current population of aphids and most of the damage has already been done.

Crapemyrtle aphids produce honeydew on which sooty mold growsPhotos: Mark Schlossberg, ProLawn Plus, Inc.

Fall SightingsSaddleback caterpillars are still active this week. Look out for them to avoid contact since they have stinging hairs that can be quite painful. Praying mantids are mating so so start looking for females with eggs. Through October, females will be laying eggs on sturdy grasses and twigs.

Ginny Rosenkranz, UME, photographed this saddleback caterpillar and this mating pair of praying mantids

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Beneficial of the WeekBy: Paula Shrewsbury, University of Maryland

Pirates attack thrips and other small insects and mites

Of course I am talking about minute pirate bugs which are predaceous true bugs (Orius tristicolor; order Hemiptera; family Anthocoridae). This past week I was out “hunting” for insects and plant damage with my IPM class and we came across a nice planting of anemones, the flowers not the sea creatures where Nemo hangs out. Of interest though is that sea anemones are named after the flowering plant because of their colorful appearance. We took the flower heads and shook them gently into plastic vials. When we looked in the vials we found thrips (plant feeders) and minute pirate bug adults. I emphasized to the students they need to separate the two types of insects quickly or they will only end up with one insect, the predator, for their collections!

Minute pirate bugs have needle-like piercing-sucking mouthparts that they impale into their prey. They then suck out the prey’s insides ultimately killing it. Adult pirate bugs are quite small (< 1/8”), oval, and black with white markings at the base and ends of the wings (see image). Minute pirate bugs undergo incomplete metamorphosis so nymphs and adults usually occur in the same location / plant and feed on similar prey items. Nymphs and adults are similar in shape but nymphs are usually yellowish-orange with red eyes (see image). Minute pirate bugs overwinter as adults and begin activity early in the season. Tiny eggs are laid into plant material and it takes about 3 weeks to develop from egg to adult. There are multiple generations of minute pirate bugs per year and they remain active until day length becomes short later in the season. Another common and related predatory bug is the insidious flower bug, Orius insidiosus.

Minute pirate bugs are considered generalist predators that feed as adults and nymphs on a wide range of prey items. They are commonly found in association with thrips, spider mites, aphids, small caterpillars, psyllids, leafhopper nymphs, whiteflies, chinch bugs (in turf), and insect eggs of many species. Pirate bugs are also omnivorous in that they feed on pollen from many flowering plant species and plant juices when prey is not available. I frequently see minute pirate bugs on marigolds feeding on pollen and in roses feeding on thrips. This suggests planting marigolds near rose beds may help to encourage predatory pirate bugs and suppress plant feeding thrips. This goes along with research based information that shows increasing plant diversity, especially plants that flower, can enhance natural enemies. Some Orius species are commercially available and used in greenhouse and conservatory biological control programs to control thrips.

An adult Orius bug with its piercing-sucking mouthpart inserted into what used to be a whitefly nymph. Photo: Jack Dykinga, http://www.ars.usda.gov

A minute pirate bug nymph. Note the wing buds (not fully developed wings) on the abdomen of the bug.Photo: Adam Sisson, Iowa State University, Bugwood.org

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Weed of the WeekBy: Chuck Schuster, University of Maryland Extension

In recent travels and across many lawns, I have been noticing yellow foxtail, Setaria glauca, a member of the foxtail family and a summer annual. This foxtail has the characteristic foxtail seed head, which will be yellow in color and produce prolific amounts of seeds. This foxtail, like the others, has a fibrous root system and stems that do not root at the nodes. Found in many settings, it will be found in turf and landscape settings, preferring fertile soil. It is a clump forming annual grass.

Yellow foxtail can be distinguished from green or giant foxtails by evaluating the hairs found on the leaf blades. Yellow foxtail has long silk-like hairs found only near the base. Giant foxtail has short hairs covering much of the upper leaf surface. Green foxtail has no hairs on the upper surface or near the leaf base.

Control of yellow foxtail can be obtained using several products which have shown good effectiveness as part of an overall landscape pre emergent plan. These products include Barriacade, Dimension, Kerb, Rout, Snapshot, Surflan, and Treflan. Post emergent control in turf can successfully be obtained using Acclaim Extra. Non-selective post emergent control can be obtained using glyphosate type products in landscape settings.

Yellow foxtails produce a large amount of seedsPhoto: Virginia Tech Weed ID Guide

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

Chelone glabra, white turtlehead, is a native herbaceous perennial that thrives in rich, wet soils and prefers partial shade. It also loves to have a lot of composted leaf material, especially if it is grown in sunny areas. It is cold tolerant from USDA zone 3-8 and grows well in moist woody areas or along a stream bed. The white, 1 inch long flowers sometimes have a tinge of pink and are shaped a bit like a snapdragon with two lips, a small under petal and a large hood-shaped petal on top that resembles the head of a turtle. They are tightly spaced at the tip of the branches and bloom from late summer into the fall. The leaves are arranged on the opposite side of the stems and are thin, lance-shaped and dark green in color. Plants can grow 1-4 feet tall, 1-3 feet wide, and will attract both humming birds and butterflies to the garden. The leaves are also a food source for the Baltimore checkerspot caterpillar. These beautiful natives can be used in rain gardens and allowed to naturalize in areas that provide moist soils and light shade. Plants are susceptible to mildew, especially if the soil has been allowed to dry out. If the shade is too intense, the plants may need to be staked up.

Turtleheads thrive in rich, wet soilsPhotos: Ginny Rosenkranz, UME

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Degree Days (As of September 21)

Annapolis Naval Academy (KNAK) 4050 Baltimore, MD (KBWI) 3703 College Park (KCGS) 3634 Dulles Airport (KIAD) 3697Ellicott City (E247) 3576 Fairfax, VA (D4092) 3946Frederick (KFDK) 3660 Greater Cumberland Reg (KCBE) 3412 Gaithersburg (KGAI) 3530 Martinsburg, WV (C1672) 3456Natl Arboretum.Reagan Natl (KDCA) 4367 Rockville (C2057) 4057 Salisbury/Ocean City (KSBY) 3807 St. Mary’s City (St. Inigoes, MD-KNUI) 4051 Westminster (KDMW) 3853

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

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

Trees Matter SymposiumNovember 1, 2017Location: Silver Spring Civic Center, Silver Spring, MDFor more information

December Pest Management ConferenceDecember 15, 2017Location: Howard Community College, Columbia, MD

Advanced IPM Short CourseJanuary 8 - 11, 2018Location: University of Maryland, College Park, MD Contact: Short Course Assistant, 301-405-3911, umdentomology@umd.edu, http://landscapeipmphc.weebly.com/

FALCAN Pest Management ConferenceJanuary 19, 2018Location: Frederick Community College, Frederick, MD

Biological Control ConferenceFebruary 1, 2018 Location: Carroll Community College, Westminster, MD

Eastern Shore Pest Management ConferenceFebruary 7, 2018Location: The Fountains, Salisbury, MD

Chesapeake Green Horticulture ConferenceFebruary 20 and 21, 2018Location: Maritime Institute, Linthicum Heights, MD

Upcoming Conferences

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

College of Agriculture & Natural Resources (AGNR) Open HouseSaturday, Oct. 14, 2017

Central MD Research & Education Center, Clarksville Facility, 4240 Folly Quarter RoadEllicott City, MD 21042

http://agnr.umd.edu/openhouse