for Arborists, Landscape Managers & Nursery Managers

Commercial Horticulture April 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

- Weather update- Ambrosia beetles- Gypsy moth hatch- Indian wax scale- Boxwood blight and new procedures at some nurseries - Emerald ash borer- Powdery mildew- Aphids and sawflies on roses- Boxwood leafminer- Lace bugs on pieris- Ant-mimic longhorned beetle- Hemlock woolly adelgid

Beneficial of the WeekWeed of the WeekPlant of the WeekDegree DaysAnnouncements

Pest Predictive Calendar

IPMnetIntegrated Pest Management for

Commercial Horticulture

extension.umd.edu/ipm

With the Warmth, Come the Bugs By: Stanton GillWe are getting emails about brown marmorated stink bugs walking about on walls of customers’ houses this week. The warmth and sunshine is making the few BMSB left around hyperactive. The BMSB went from a superstar 8 years ago to a nuisance problem in 2017. Predators and parasites are doing a great job at keeping this invasive species down in numbers.

Eastern tent caterpillars are plowing through foliage on susceptible trees this week consuming foliage of cherries and crabapples at rapid rates with the increased temperatures.

People are sending in pictures of several species of pyralid moths on window panes and attached to walls in the morning hours. The adults are flying during the warm nights and attracted to the lights of residential houses.

The warm weather is also bringing many trees, shrubs and herbaceous plants into bloom, like this redbud at the U.S. National Arboretum

2

Gypsy Moth Hatch - Eastern ShoreRob Clarke, Maryland Forest Service, DNR, reported gypsy moth hatch on April 10 in Berlin. Rob only found a single egg mass of freshly hatched caterpillars at a woodland site. If you haven’t seen egg hatch yet, but do find egg masses, scraping them off the trunk is an effective method of control.

A sampling of the ambrosia beetles found in our alcohol trap earlier this week

First instar gypsy moth caterpillars hatched from an egg mass on chestnut oak (2005)

Ambrosia Beetles Update By: Stanton GillOn Thursday I received trap catches from Harford County, Frederick County, and Montgomery County. The traps in Harford County contained Xyleborinus saxesenii, several Xylosandrus germanus, and one Xylosandrus crassiusculus. This is the first X. crassiusculus I have received this season. The Fort Detrick site, sent in by James Becker, had several Xyleborinus saxesenii and a couple of Xylosandrus germanus. The site in Montgomery County contained mainly Xylosandrus germanus. Management: For commercial applicators, now is the time to apply Onyx Pro (bifethrin) or permethrin to the trunk of susceptible tree species. We received information that Bonide has a permethrin product that is a non-restricted use material. You will need to check different locations for availability in your area.

Indian Wax ScaleSteve Castrogiovanni, Mead Tree and Turf, found Indian wax scale on buckeye in Gaithersburg on April 11. Keep an eye out for Indian wax scale after a fairly mild winter. We are getting reports of viable populations this spring. Check to see if females are alive by flipping over the waxy covers. The adult female is a bright red color. Crawlers are active in June in Maryland. Due to its waxy covering during most the year, it is best to apply control measures to this scale during the crawler stage. There is only one generation per year.

Flip Indian wax scale covers to see if the female is alive - she will be bright redPhoto: Steve Castrogiovannia, Mead Tree and Turf

3

Boxwood Blight and New Blight Prevention Program in Maryland By: Stanton GillMDA is working with 6 Maryland nurseries to set up a program to prevent boxwood blight from entering their nurseries. I visited the first nursery in Maryland to enter into the program this week. It is a certification program in which the nursery manger/owner does everything possible to quarantine the boxwood plants, while at the nursery, so landscape managers can buy plants that are less likely to have the disease. Our neighbor, Pennsylvania, has banned shipment of boxwood into their state unless it is under some sort of boxwood blight quarantine assurance program.

What You Need to Know as Boxwood Purchaser In the past, if you visited your local nursery you could generally breeze in and purchase plants without too much trouble. Now, if you purchase from a nursery under this quarantine /certification program you must read their signs when you enter the nursery. The signs will direct you to call one of their managers and you report to their main office area. They will escort you through the nursery, and if you need to enter the boxwood quarantine area you will have to put on a Tyvek suit and booties. In this way, the nursery can more assuredly provide boxwoods that are free of boxwood blight.About the Disease The first description of boxwood blight was from the United Kingdom in the mid 1990s. In 2002, the disease was discovered in New Zealand, and the cause was identified as a new species of fungus which was formally named Cylindrocladium pseudonaviculatum. The fungus causing the disease in the UK was later named C. buxicola. These pathogens are now known to be the same. Boxwood blight is found throughout Europe, and has spread to North America. In October 2011 the blight was found in North Carolina and Connecticut. By January 2012 it had also been identified in Virginia, Maryland, Rhode Island, Massachusetts, Ohio, Oregon, Pennsylvania, New York and British Columbia.

Hosts There appears to be some tolerance to the disease within the Buxus genus. In general, the boxwood varieties within the species B. sempervirens tend to be more susceptible to this disease.

Powdery MildewPaul Wolfe, Integrated Plant Care, reported powdery mildew on euonymus this week. Sunny days and cool nights are ideal for powdery mildew.

Emerald Ash Borer By: Stanton GillBob Mead, Mead Tree and Turf, and John Austin, Green Gardens, called in to report a lot of ash trees that are dying back in the upper parts of Montgomery County this spring. Large plantings of the green ash made in Montgomery Village and Germantown in the 1970s and 1980s are now succumbing to EAB attacks. John Austin reported that trees that were being attacked had a distinct yellow-orange cast to the trunks. He cut away bark and found larvae of EAB infesting the trees.

Powdery mildew on euonymus

4

Predators often show up to help control aphid populations early int he seasonPhoto: Jessica Frakes, Thrive, Inc.

Boxwood Leafminer By: Stanton GillThe dreaded boxwood leafminer adults emerged on April 11 in Bethesda. Paul Wolfe, Integrated Plant Care, called in to report adults buzzing up an down over his customer’s boxwood plants. Adults have not emerged yet here at the research center in Ellicott City. The adults will be active for about 7 – 10 days. Some landscape managers attempt to treat the adults with Avid or a synthetic pyrethroid when the adults are flying. MainspringGNL is also an option as a foliar application. If this works for you, this is great. The adults will lay their eggs in the foliage and the larvae will hatch within 2 weeks after laying. The larvae feed in May until it becomes hot, then they go into a resting stage. A systemic insecticide can be applied to the soil now so the hatching and feeding early instar larvae would be killed.

Lace bug nymphs are active on pieris

Lace Bug on PierisBy: Stanton Gill

Paul Wolfe, Integrated Plant Care, reported hatching of pieris lace bug on April 11 in Bethesda. The lace bugs overwinter as eggs in the leaves. Control is fairly easy. If you direct a 2% horticultural oil to the undersides of the foliage, it is effective. You can also use systemic insecticides to control this bug.

Insects on RosesJessica Frakes, Thrive, Inc., found aphid and roseslug sawfly activity beginning on roses in Washington D.C. on April 13. Look for predators such as syrphid flies and lady bird beetles that will help manage the aphids.

Sawfly larvae skeletonize foliage by etching off the upper surface between the veins. Feeding by later instars creates larger holes and can defoliate plants. Look closely on the upper side of the leaves for the small sawfly larvae at this time of year. There are three species of sawflies that are commonly found feeding on roses in Maryland. Conserve and Orthene can be used for sawfly control.

Even though small, leafminer adults are easy to spot since they are such a bright orange; they are emerging at this time

5

These longhorned beetles mimic ants as they move quickly on woody plantsPhoto: Jon Yuschock, Bugwood.org

Look at the waxy masses of hemlock woolly adelgids to see if eggs or crawlers are present; a crawler and eggs are in the photo on the right

Cyrtophorus verrucosus: Ant-mimic Longhorned BeetleOrder: Coleoptera; Family: Cerambycidae

If you run across this longhorned beetle this spring have no fear. These adult ant-mimic longhorned beetles are just looking for nectar or pollen of spring flowering trees and shrubs. The larvae feed on dead hardwoods, including Acer, Betula, Carya, Castanea, Cercis, Cornus, Fagus, Quercus, Ulmus, and Pinus. Their common name certainly becomes them as they are star performers of mimicking an ant’s movements….running here and there. The adult beetle is ~ 1/3” long.

Hemlock Woolly Adelgid (Adelges tsugae) Crawlers (or newly hatched nymphs) of the hemlock woolly adelgid (HWA) were found on an eastern hemlock in Columbia on April 10 at 196 GDD. Native to Asia, hemlock woolly adelgid can infest all species of hemlocks, but it is a major pest of eastern and Carolina hemlocks, often killing them. An infestation of HWA can be easily detected by the large amounts of fluffy white wax resembling cotton balls located on hemlock twigs at the base of the needles. The cottony masses cover the adult female body and her eggs. HWA is a small aphid-like insect; adult females are about 1/16 inch long, black, oval, soft bodied; newly hatched nymphs are reddish-brown with a white fringe near the front; and settled crawlers are black with a white fringe around the body and down the back. There are two generations a year. Hemlock woolly addelgid damage plants by inserting their stylet mouthpart into the phloem of the tree and removing plant fluid.Control: Spray trees with 2% horticultural oil or insecticidal soap to target crawlers or newly settled crawlers. Other insecticides that can be applied as sprays include Dinotefuran (Safari) and Acetamiprid (Tristar) as a foliar spray.

For more information on hemlock woolly adelgid go to: https://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/ipmnet/HemlockWoollyAdelgid-UMD.pdf

6

Beneficial of the WeekBy: Rebeccah Waterworth and Paula Shrewsbury, University of Maryland

What is eating my lawn chair?On another recent trek across campus, I (Rebeccah) detoured across the lawn to my final destination. There was a nice looking patch of flowering dandelions that I was certain would have interesting visitors. It was a warm sunny afternoon which meant perfect conditions to observe six-legged critters. (By the way, this is how you tell who the entomologist is in a crowd of people. They are the only ones staring at a dandelion flower without pulling it out!) There were some small native bees gathering pollen, but my gaze shifted when I saw the movement of a much larger bee nearby, which turned out to be a common Eastern carpenter bee, Xylocopa virginica (Order Hymenoptera, Family Apidae) (Fig. 1). Paula and I recently wrote an article about bumble bees (March 31st), which look similar to carpenter bees. However, I knew that I was looking at a carpenter bee because it had a shiny, and not hairy, abdomen. It is also possible to tell male and female carpenter bees apart if you can look at their faces. Male carpenter bees have a yellow patch on their face between their large eyes (Fig. 2). This bee foraging on dandelions was a male.

This species is the only large carpenter bee in our region. The male that I saw had overwintered as an adult in a nest on campus. He may or may not have yet mated with a female carpenter bee. After the weather has warmed a little, mated female carpenter bees will return to an existing nest site or gallery and clean it to lay her own eggs. Sometimes, this nest is the same one in which this mother bee had been raised! When a female has to build her own nest, she locates a piece of solid wood (softwoods are preferred) and chews a ½” diameter round hole with her strong mandibles (jaws). After chewing for about an inch or about one body length, she turns 90°, and with the grain, she continues to chew and remove the wood for at least 12 inches to create the cells where she will oviposit (lay eggs). A female never eats the wood that she is excavating, but she might use the shavings to create the walls between cells in her nest, similar to particleboard. Within each cell, she will place some bee bread, a mix of pollen and regurgitated nectar, and lay one egg, after which she seals in everything. A female bee will lay between six to ten eggs by July. Larvae feed only on the bee bread and later pupate. The new generation of carpenter bees will emerge from the nests in August. These young bees visit flowers through the end of the summer, but return to their nest each night and overwinter there as well. There is only one generation of carpenter bees each year in the mid-Atlantic.

People may have run-ins with carpenter bees in a couple of ways. First, as the title of this article suggests, carpenter bees often nest in human-made structures, including telephone poles, porch and deck wood, roof eaves, windowsills, and even lawn furniture. In fact, Xylocopa is Greek for “wood-worker.” Solid softwood

Fig. 1. An Eastern carpenter bee, Xylocopa virginica, visiting a flower in Wheaton in August 2016 Photo: R. Waterworth, UMD

Fig. 2. A male (left) and female (right) Eastern carpenter bee. Note the large yellow patch on the face of the male bee. Males also have much larger eyes compared to females. Large eyes are needed to find females and to see intruders in their territories. Photo: R. Waterworth, UMD

7

is especially susceptible if it is unpainted or unvarnished. I was watching a carpenter bee excavate her nest in May 2016, and she decided that a weathered wooden plant stake (2” by 2”) in the middle of the field was a good location. Bees have about a 2” minimum thickness for their nesting site, so some thinner pieces of wood are likely unusable. Single nests are probably unlikely to cause structural issues, but through the reuse and expansion of nests over time with later generations, carpenter bee activity may lead to structural problems. If not nesting among our structures, they would nest in solid wood, stumps, logs, or dead trees.

People may have a second interaction with carpenter bees in the spring when they encounter the territorial males. When females select their nesting sites, male bees attempt to keep competitors away, as they do not want other bees to mate with their females. They will hover a few feet from nest entrances to keep an eye out for trespassers. The act of defending their territory may include “dive bombing” anything that is seen as a threat. Despite the fact that we look nothing like a carpenter bee, we can be carefully inspected if we haplessly wander into their territory. Despite their intimidating size, please don’t fear them! Males do not sting and are essentially bluffing their way through life. You can even hold male carpenter bees, which is another favorite pastime of many entomologists (me) who are showing off in front of non-entomologists (my sisters).

You may be wondering how carpenter bees can be beneficial if they nest in your favorite lawn furniture or attack you in your yard. Well, the answer to that is the ecosystem service that they provide. They are extremely efficient pollinators. The Eastern carpenter bee is an inch long and can carry enormous bushels of pollen as they forage in our landscapes. They are generalist pollen feeders and are known to visit an excess of 50 different flowering plants in some areas. They also will exhibit flower constancy, visiting the same types of flowers repeatedly, especially during nest preparation. In other areas of the world, other species of carpenter bees are important pollinators of passion fruit, Brazil nuts, greenhouse-produced tomatoes, and cotton. They are also among many bees that can be “nectar robbers.” As the result of their size, they are unable to enter many small tubular flowers, such as Penstemon and Salvia, so with their mandibles, they cut a small hole in the base of the petals and lap out the nectar with their tongue. This is done without ever having entered the flower to pick up pollen. If enough nectar is robbed from flowers, this will make them unattractive to other bees that might have visited to pollinate.

We hope that you enjoy your interactions with all bees this season and know that they are working really hard in your landscape pollinating plants. However, while I marvel at what bees are able to accomplish despite their small size, I will always make sure that my lawn chairs stay painted!

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

The weather has continued to warm up. Crabgrass has been found germinating at Swann Point, Ellicott City, and Lutherville Maryland. A plant that is being seen in the landscape and turf now is common speedwell. Common speedwell, Veronica officinalis, is also know common gypsyweed or heath speedwell. It is a member of the plantain family and is a perennial plant introduced from Europe. While known by many as a desired herb, it can also be a weed when in an undesired setting. It will establish itself in disturbed soil areas growing to heights of twelve inches. This plant will form a dense horizontal mat, with hair covered stems that will root at the nodes. Leaves are opposite and are found with two occurring at each node, being elliptical in shape, up to two inches in length and to one and one

Reports are coming this week of crabgrass germinatingPhoto: Rick LaNore/James LaNore, MRW Lawns

8

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

Cedrus deodara ‘Electra Blue’, often called deodar cedar or Himalayan cedar, is an upright pyramidal evergreen with 1 to 2 inch long silvery blue needles that encircle the branches and grows 30 -40 feet tall and 15-30 feet wide. The branches spread in a soft horizontal curve downwards, with the ends drooping gracefully at the tips. The foliage starts out as a soft powder blue in the spring that matures to a silver blue in summer and stays on the tree for 3-6 years. It is cold tolerant from USDA zones 6 - 10 but needs some protection from strong winter winds, and it is the best choice of true cedars in hot and humid summers. Cedrus deodara ‘Electra Blue’ needs full sun and will tolerate both dry and moist growing conditions once established, but it doesn’t tolerate standing water. It is also tolerant of many soil types and pH, and slightly tolerant of urban pollution and said to be resistant to deer. The photo was taken at the U.S. Botanical Garden in the National Garden close to the Butterfly Garden in Washington, DC. This tree has no serious insect or disease problems and is Verticillium wilt resistant.

Cedrus deodara ‘Electra Blue’ is a good choice for regions with hot and humid summersPhotos: Ginny Rosenkranz, UME

half inches wide. It prefers drier soils, rough areas that are not often well managed and lack proper fertility. The flowers are produced on stalks and are small, blue to white in color with five petals. Flowers occur from late April through June most years. Control of common speedwell starts with fertility management. In turf areas, work to maintain a dense turf with appropriate pH and nitrogen management. In landscape settings, the use of mulch will help prevent the small seeds from receiving the necessary UV light for germination. In turf, use post emergent selective products including 2,4Dm MCPP (Mecopropp). In landscape areas, non selective post emergent products will help control those plants that escape the mulch. Use caution with these products near desired species of plants.

For photos of common speedwell, see the Maryland Biodiversity Project site.

9

Degree Days (As of April 12)

Annapolis Naval Academy (KNAK) 218 Baltimore, MD (KBWI) 225 College Park (KCGS) 213 Dulles Airport (KIAD) 251Ellicott City (E247) 223 Fairfax, VA (D4092) 281Frederick (KFDK) 199 Greater Cumberland Reg (KCBE) 200 Gaithersburg (KGAI) 190 Martinsburg, WV (C1672) 171Natl Arboretum.Reagan Natl (KDCA) 326 Rockville (C2057) 294 Salisbury/Ocean City (KSBY) 242 St. Mary’s City (St. Inigoes, MD-KNUI) 276 Westminster (KDMW) 227 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

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

LOCATION

Camellia japonica ‘Jerry Hill’ Full bloom Ellicott City (April 10)Cercis canadensis (Eastern redbud) Full bloom Ellicott City (April 13)Liriodendron tulipifera (tuliptree) First leaf Ellicott City (April 14)Podophyllum peltatum (mayapple) First leaf Ellicott City (April 12)Sassafras albidum Full bloom Ellicott City (April 10)

Phenology

Check Out The Pest Predictive Calendar

Posted in 2016, this Pest Predictive Calendar is intended to assist landscape managers, growers, IPM professionals and others in predicting the appearance of pest insects and mites in order to make more timely management decisions. By using the Plant Phenology Indicators (PPI) and Growing Degree Days (GDD) on this table you can anticipate when the susceptible life stage(s) (stage you want to target for control measures of pest insects and mites are active.

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

Eastern Shore Pest WalkMay 11, 2017Contact: Ginny Rosenkranz, 410-749-6141

MAA/UMD Extension Evening Plant Diagnostic ClinicMay 23, 2017Location: Cylburn Arboretum, Baltimore, MD Contact: 410-321-8082

Pesticide Recertification Conference (Eastern Shore)June 2, 2017Location: Wye Research and Education Center, Queen-stown, MDhttps://2017esprocrastinatorspest.eventbrite.com

Pesticide Recertification ConferenceJune 9, 2017Location: Montgomery County Extension Office, Derwood, MD

MNLGA Nursery Field DayJune 29, 2017Location: Ruppert Nurseries, Laytonsville, MD