for Arborists, Landscape Managers & Nursery Managers

Commercial Horticulture June 6, 2014Coordinator 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 (Regional Specialist, Wye Research & Education Center)Design, Layout and Editing: Suzanne Klick (Technician, CMREC)

In This Issue...

If you work for a commercial horticultural business in the area, you can report insect, disease, weed or cultural

plant problems found in the landscape or nursery to

sklick@umd.edu

TPM/IPM Weekly Report

Weather UpdateThe weather for the last three weekends has been perfect and garden centers are reporting strong sales on Fridays, Saturdays, and Sundays. The cool weather and sunshine are creating perfect conditions for customers to buy plants. The rains have been frequent, but mainly confined to the weekdays so it is generally working out well. This change in weather is great news after the dismal sales period in March and April. More nice weather is also forecasted for this coming weekend.

- Weather update- MDA Pesticide Container Recyling Program- More on winter damage- Increasing bear population- Japanese beetle grubs- Privet rust mite- Problems with barberry- Fireblight- Impatiens downy mildew- Scale upate- Rose rosette disease- Brown marmorated stink bug- Mimosa webworm- Gypsy moth activity- Fertilizer applicator seminar- MGGA greenhouse tour and picnic

Beneficial of the WeekPhenologyDegree DaysAnnouncements

IPMnetIntegrated Pest Management for

Commercial Horticulture

extension.umd.edu/ipm

Maryland Department of Agriculture Pesticide Container RecylingMDA has a brochure on the dates and details of the pesticide container recycling program which is available at: http://mda.maryland.gov/plants-pests/Documents/recycle.pdf

2

A crape myrtle photographed on June 3 that is late leafing out in GlyndonPhoto: Mark Schlossberg, ProLawn Plus, Inc.

Increasing Bear PopulationThere was an interesting article in The Washington Post on Tuesday, May 27th, addressing the increasing black bear population in Maryland. The black bear is making a comeback in Maryland. There are fairly good populations in Garrett and Alleghany Counties and growing populations in Washington and Frederick Counties. Now, bear sightings are popping up in Carroll and Montgomery Counties. Last year, we received an e-mail from a beekeeper in Damascus (Montgomery County) that suffered damage from bear. He said it looked like vandals had trashed his supers (part of a beehive). DNR official confirmed the bear damage and he was given financial assistance to construct a wire fence to surround his bee hives.

More on Winter DamageBernie Mihm Jr., Fine Earth Landscape, sent in the comments below about what he is finding regarding plants and winter damage:

Gardenia ‘Frost Proof’ is not, at least not in our area. I planted some at two residences in Chevy Chase and Bethesda last year. Both instances were at client’s request. All plants died. Figs. A week ago all three of my figs looked dead. Just this week, two small ‘Chicago Hardy’ figs have started growing back out from the roots. My “brown turkey” fig hasn’t shown any sign of life despite being more established and growing on the southern side of our home.Crape Myrtle. Two ‘Tuscarora’ crape myrtles, planted in 2002 in upper Montgomery County, also looked dead a couple of weeks ago but, since many of the stems were still green, I waited on these as well. Now they have leafed out on about a quarter of the branches, even near the top. I’m waiting to see if some of the other branches leaf out.Magnolia grandiflora‘Hasse’ were planted in 2002 in upper Montgomery County. Full exposure with plenty of wind. It shows absolutely no damage.Magnolia grandiflora ‘Claudia Wannemaker’ planted in mid fall 2014 in Chevy Chase. There is minimal leaf burn and no stem damage at all.Nellie Stevens Holly planted summer and mid fall 2014 in Chevy Chase. There is minimal winter leaf burn and no stem damage.

Based on past experience, I am guessing that the wet winter, which put lots of moisture in the ground, held down the damage to the broadleaf evergreens.

Tony Murdock, Fine Pruning, is reporting complete dieback of yuccas in the Frederick area.

Crape Myrtle DiebackWe are still getting in pictures of winter damage on crape myrtles. In many locations people are reporting a very late leaf out. So far, the white flowering varieities appear to have less dieback than pink and red flowering cultivars.

3

Problems with BarberryBarberry may be a nice looking plant and is sold by many garden centers, but you might want to consider not growing or selling this plant due to its invasive nature. Berberis thunbergii is a prolific seed producer and its seeds are estimated to have a 90% germination rate. Birds eat the seeds and carry them for a few hundred yards, depositing them in areas where the Japanese barberry can take hold and quickly choke out most other plants.In many states, including Maryland, the barberry is getting established in wooded areas.

According to recent studies by scientists Jeffrey Ward and Scott Williams at the Connecticut Agriculture and Experiment Station (CAES), eliminating stands of Japanese barberry from forested areas can reduce the number of Lyme disease-infected ticks on the property by 80%. It seems that stands of Japanese barberry retain humidity. Ticks need an environment with about 80% humidity to actively feed, quest and reproduce. By measuring humidity levels above and at ground level under the barberry foliage, Ward and Williams found humidity levels under Japanese barberry dipped below 80% for only one hour per day. In open, sunny areas with no Japanese barberry, the exact opposite is true. The humidity levels rise to 80% for only one hour each day.

White-footed mice, a known apex host for Lyme disease also thrive under the canopy of Japanese barberry. The combination of mice and a tick population that is active almost all day long appears to be a potent mix that is leading to a public health epidemic in many states.

Fireblight on callery pearPhoto: Mark Schlossberg, ProLawn Plus, Inc.

FireblightFireblight is visible on apples and callery pears this week. Mark Schlossberg, ProLawn Plus, Inc., is finding it on callery pears in Owings Mills this week. Conditions were optimal earlier in the spring during the infection period.

Privet rust mites, Phytoptus avellanaeMarty Adams, Bartlett Tree Experts, found privet rust mites on a privet on June 5 in Catonsville. Female mites overwinter under bud scales. The females laid eggs in May and the immatures are now active. They are yellow to white and spindled-shaped. This eriophyid mite can build up to high numbers in spring. The mite only has two pairs of legs.Monitoring: Damage appears as russeting of foliage rather than a coarse chlorotic fleck like other mites. The leaves will often cup and twist.Control: Horticultural oil, insecticidal soap, and Avid

Japanese Beetle UpdateWe are still finding later instar grubs in turfgrass this week. We have not found any beetles pupating yet. We do expect to see a fairly large population of Japanese beetles sometime in late June to early July. If you find them pupating or emerging in your area let Stanton know at sgill@umd.edu, 410-868-9400.

4

Alternatives to garden impatiens include: Caladium, Torenia, Coleus ‘Red Ruffles’ and Stained GlassworksTM ‘Trailing Plum’ (shade tolerant cvs) and Begonia

Impatiens Downy MildewImpatiens downy mildew has been reported on plants in retail outlets in nearby states recently, so if you grow or plant garden impatiens, be alert for symptoms of this disease. Impatiens downy mildew, caused by the fungus-like microorganism Plasmopara obducens, is favored by cool, moist conditions, and affects both seed and cutting propagated garden impatiens, Impatiens walleriana. New Guinea impatiens are tolerant of this disease. Look for slight light green mottling or stippling on one or a few leaves as the early symptoms of impatiens downy mildew. Infected leaves may curl downward. If you look at the undersides of these leaves, you will see the white fuzzy growth of the pathogen. As the disease progresses in the landscape, infected plants will be stunted, and leaves and flowers drop off leaving bare, leafless green stems. Greenhouse growers who produce garden impatiens should use a fungicide rotation program throughout the production cycle to protect plants from downy mildew infection (for examples of such fungicide programs, see this information from the University of Massachusetts). However, fungicides do not cure infected plants, so all symptomatic plants must be bagged and discarded. It is very important to scout impatiens regularly for symptoms, making sure to check the undersides of leaves. In the landscape, remove infected plants and all plant debris, and plant other annuals in the beds. Avoid planting garden impatiens in a bed with a history of the disease, as the pathogen produces thick-walled spores that may overwinter in plant debris. Take this opportunity to try other shade tolerant plants like coleus, begonia, caladium and torenia.

We are interested in knowing the extent of this disease in our area. If you think you have impatiens downy mildew in greenhouse or landscape plantings, please contact me (Karen Rane) at the UMD Plant Diagnostic Lab (phone 301-405-1611, email rane@umd.edu).

5

Scale Update*By: Nancy Harding, UMD

White Prunicola Scale (WPS), Pseudaulacaspis prunicola (armored scale) Monitoring WPS on Prunus × yedoensis (Yoshino cherry) in Laytonsville on Tuesday, June 3rd, found the majority of the scales were 2nd instars. The Degree Days in Laytonsville as of June 3rd were 669DD. Second instar scales cover themselves with a hard protective wax covering (armor) that is produced from their continued feeding thus rendering IGRs not very effective. If the degree day accumulations in your area are similar to Laytonsville, the threshold for optimal treatment has likely passed.Monitoring: We will continue to monitor WPS and report when the 2nd generation (of three) crawlers are active which we predict will occur in early to mid-July. Be sure to also check cherry laurel plants at your landscape sites. We receive a lot of reports of this scale on cherry laurel.

Pine Oystershell Scale, Lepidosaphes pini (armored scale)Last week we reported CRAWLER activity of the pine oystershell scale on Pinus densiflora (Japanese red pine) in Laytonsville. This week, Tuesday June 3rd, we found a high percentage of crawlers and settled crawlers (1st instars). The Degree Days in Laytonsville were 669DD. If the degree day accumulations in your area are similar to Laytonsville, and you have not already treated, there is still time to apply a control.Monitoring: Monitoring for crawlers and settled crawlers will be challenging as they tend to “hide” deep in the needle sheaths. Look carefully, in Fig 1 - the needle shealth has been pulled away to expose the crawler (higher on the pine needle) and the settled crawler (lower on the pine needle). The adult female cover is oyster-shell shaped (see Fig 2), straight or slightly curved, moderately convex, and light brown. The body of the female is white; eggs and crawlers are white. It has been reported that there are two generations a year; however there is little known about the life history of this species. Damage of the scale’s feeding causes chlorosis at the base of the needles.Control: When crawlers are active, apply pyriproxyfen (Distance) or buprofezin (Talus) mixed with 0.5 - 1% horticultural oil for control.

Japanese Maple Scale (JMS), Lopholeucaspis japonica (armored scale)We received our first report of CRAWLER activity in the Frederick area on June 6. Degree Days at this location on June 5 were 717. Use a hand lens to look for the light purple crawlers (as shown in photo). Control: Applications of 0.5 - 1% horticultural oil and pyriproxyfen (Distance) or buprofezin (Talus) should be made when crawlers are detected. This treatment should have about 2 - 3 week residual activity. At that time monitor your plants again to see if crawlers are still active. The twice-stabbed lady bird beetle provides some biological control of this scale.

The pine needle sheath has been pulled away to expose an active crawler (top arrow) and settled crawler (bottom arrow)

The adult female can be oyster-shell shaped, straight, or slightly curved, moderately convex and light brown.

6

Cottony Camellia Taxus Scale, Pulvinaria floccifera (soft scale)Paul Wolfe, Integrated Plant Care, found CRAWLERS of cottony camellia taxus scale on hollies in Bethesda on June 4. Degree Days were 970. We have received a few reports and samples from others of this scale, but no other reports of crawler activity at this time. Continue monitoring this scale closely for yellow crawlers. The scale tends to accumulate on the undersides of foliage.Control: Wait for eggs to hatch and then treat with pyriproxyfen (Distance) or buprofezin (Talus) mixed with 0.5 - 1% horticultural oil.

Calico Scale, Eulecanium cerasorum (soft scale)Stephen Griner, Scientific Plant Service, found calico scale in Sparks on June 4. Tony Murdock, Fine Pruning, is also finding calico scale on mimosa in Shepherdstown, WV. Crawlers for this scale should be active soon. Monitor plants for copious amounts of honeydew in late May and early June. Look for the oval-shaped, yellow-bodied crawlers in June.Control: When crawlers are out, options include pryriproxyfen (Distance) or buprofezin (Talus) with 0.5 – 1% oil.

Oak Lecanium Scale, Parthenolecanium quercifex (soft scale)Monitoring oak lecanium scale on Quercus phellos (willow oak) on Monday, June 2nd in College Park found many active CRAWLERS on branches with some migrating to the underside of the foliage where they will settle along the midrib and veins of the leaves. These settled 1st instars will molt into the second instars and move back to the twigs in late summer to spend the winter and hibernate under a then, waxy shield. The Degree Days in College Park on June 2nd were 537DD.Monitoring: Check the degree day accumulations in your area. If they are close to 537DD, you should look (using a hand lens) for active crawlers on the branches and for settled 1st instars on the leaves. In addition, flip the female scale bodies over to determine if there are still eggs or if they have all hatched. If the majority of the eggs have hatched (crawlers) and/or have become settled 1st instars, now is the time to treat. For optimal control, under these conditions, applications should be applied within the next 7-10 days. Control: Apply pyriproxyfen (Distance) or buprofezin (Talus) mixed with 0.5 - 1% horticultural oil for control.

Look for egg sacs and crawlers of cottony camellia taxus scale on yews, hollies camellias, rhododendrons, Japanese maples, and mulberries

Calico scale produce copious amounts of honeydew. Check plants for honeydew and sooty mold.

Yellow crawlers on twig/branch (top) and female scale cover flipped over showing eggs and crawlers (bottom)Photos: Nancy Harding, UMD

7

Grady Reed, Thrive, Inc. reported that he is finding rose rosette disease this weekPhoto: Grady Reed, Thrive, Inc.

Rose Rosette DiseaseWe are receiving pictures of roses with distorted new growth- clusters of shoots (like a witches’ broom) that are often reddish in color, and stems with excessive thorniness. Many of the plants are in commercial plantings and the roses are bush type landscape roses. These are the symptoms of rose rosette disease. Rose rosette has been around for several decades, but the causal agent, a virus, was only recently described. The virus is spread by an eriophyid mite. The disease was once thought to be an excellent biocontrol agent for the invasive multiflora rose, but we know now that many cultivated roses are also susceptible. Infected plants do not generally recover and plants found to be diseased should be removed from the landscape. Rose problems that can sometimes be mistaken for rose rosette include early infections of powdery mildew and injury from the herbicide glyphosate.

Brown Marmorated Stink Bug (BMSB) HatchAdam Colgan, On The Green, found recently hatched nymphs of brown marmorated stink bugs on maple in Waldorf on June 4. The stink bug population here at the research center in Ellicott City has been much lower this spring than previous years.

BMSB tend to lay 26 to 28 eggs at a time in an arrow shape. First instars are orange/red and black

A second instar nymph is black, but still has the white banding on the antennae

Cottony Maple Scale, Pulvinaria innumerabilis (soft scale)Craig Greco, Yardbirds, Inc., found CRAWLERS active of cottony maple scale on maple in Ashburn, VA on June 6. Degree days on June 5 were 681. Look for the yellow crawlers on the undersides of leaves. Preferred plant hosts include maple, dogwood, elm, hawthorn, sycamore, and linden. The crawlers are yellow. Look for them now on the undersides of leaves.Control: Talus or Distance with 1% oil.

*Degree data totals as per Weather Channel website (http://www.weather.com/out-doors/agriculture/growing-degree-days/USMD0045)

Cottony maple scale on maplePhoto: Craig Greco, Yardbirds, Inc.

8

Mimosa webworm and webbing

Gypsy moth defoliation, close-up of caterpillar and egg mass on trunkPhotos: Luke Gustafson, Charles County Master Gardener Coordinator

Gypsy Moth ActivityLuke Gustafson, Master Gardener Coordinator in Charles County, is reporting gypsy moth activity in White Plains. Several large oaks were almost completely defoliated.

Webbing from mimosa webworms on mimosa tree. Also look for this caterpillar feeding and damaging honeylocust.Photo: Tony Murdock, Fine Pruning

Mimosa WebwormTony Murdock, Fine Pruning, found first generation mimosa webworms and webbing on a mimosa in Shepherdstown WV. Mimosa webworm, Homadaula anisocentra, feeds primarily on the leaves of mimosa and honeylocust trees. Mature larvae from this first generation pupate in mid- to late July and the second generation of adults should appear in August. Second generation larvae are active during August and early September. Larvae from this generation may be so abundant that they web leaves throughout the entire crown of the tree causing it to look completely brown. Watch to see if there is activity in your area. Depending on the size of the caterpillars, it may be too late to apply anything for this generation, but monitor for the next generation. Spinosad or Bt applied when they first start feeding should give good control. Acelepyrn is a systemic for caterpillar control and should give excellent control. This caterpillars disfigures foliage, but it does not kill the tree.

9

Beneficial of the Week By: Paula Shrewsbury

What likes to kill white grubs? White grubs are the immature stage of scarab beetles. Many white grubs are pests because they feed on the roots of turfgrass which stress and kill turfgrass. These scarab beetles include Japanese beetles, masked chafers, oriental beetles, and others. The last few years have been good for white grubs and therefore bad years for turf managers. My “prediction” is that this that white grubs will do well this year too. The appropriate time to monitor for grubs is usually during the month of August, starting in early August. You want to estimate your white grub infestations before they cause significant damage. Be aware that in addition to monitoring for the white grubs themselves, you should also be monitoring for signs of natural enemies. There are numerous predators, parasitoids, and entomopathogens that attack and kill white grubs. Today I want to discuss a fungal pathogen, Metarhizium anisopliae. Metarhizium is a fungus that grows naturally in soils throughout the world and causes disease in a diversity of insects. There are specific strains associated with white grubs. Metarhizium is also produced commercially and used as a formulated biological control for a variety of insects. The way the fungus works is interesting. The fungus produces asexual spores or conidia in the soil. The spores come in contact with a host insect, the spores germinate, and the hyphae that emerge penetrate the exoskeleton of the insect or enter the insect through body openings such as spiracles. Many entomopathogenic fungi produce enzymes that assist in breaking down or “softening” the cuticle so the hyphae can penetrate more efficiently. The fungus develops inside the body of the insect. The fungus consumes the contents, and often produces chemicals with insecticidal effects which kill the insect. While this is happening, the insect body turns a red color. As the fungus grows the mycelia fill the body, the white hyphae emerge from the body and after a few days produce spores which are green in color. These spores go back to the soil and the cycle starts again. When monitoring for white grubs always watch for signs of pathogen activity. These signs include a change in color, size, and/or shape of the body. Metarhizium is one of many natural enemies of white grubs. Be sure when making turf management decisions to choose practices that will not be detrimental to natural enemies.

To see a photo of Metarhizium infecting an insect, go to http://www.biocontrol.entomology.cornell.edu/pathogens/Metarhizium.php

Professional Fertilizer Applicator Recertificiation SeminarLocation: Maryland Department of Agriculture, Annapolis, MDTime: 9:30 a.m. to 11:30 a.m.

Choose any one of the following dates for recertification:June 23, 2014August 7, 2014September 3, 2014

Seating is limited, register now.Cost: $12, which includes breakfast

See http://mda.maryland.gov/fertilizer for details and registration form (pdf link on right sidebar in section with blue map of Maryland). This program is open only to currently Certified Professional Fertilizer Applicators (turfgrass). Attending one of these seminars satisfies the continuing education requirement for renewing certification for the July 2015 - June 2016 year.

Registration with payment is required no later than one week before the class date. For more information, call 410-841-5959.

10

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

LOCATION

Amsonia hubrichtii Full flower June 4 (Silver Run)Amsonia tabernaemontana First flower June 4 (Silver Run)Astilbe x arendsii ‘Granat’ First flower June 4 (Silver Run)Chionanthus pygmaeus Full flower June 4 (Silver Run)Clematis ‘Westerplatte’ First flower June 4 (Silver Run)Cotinus obovatus First flower June 4 (Silver Run)Galax aphylla Full flower June 4 (Silver Run)Indigofera amblyantha Full flower June 4 (Silver Run)Kalmia angustifolia ‘Royal Dwarf’ Full flower June 4 (Silver Run)Kalmia latifolia First flower June 4 (Silver Run)Rhododendron maximum ‘Roseum’ Full flower June 4 (Silver Run)Scutellaria serrata Full flower June 4 (Silver Run)Stewartia pseudocamellia Bud with color June 6 (Ellicott City)Stranvaesia davidiana ‘Prostrata’ Bud with color June 4 (Silver Run)Stranvaesia davidiana ‘Winterthur’ Bud with color June 4 (Silver Run)

Degree Days (As of June 5) 2014 2013 2012 Baltimore, MD (BWI) 720 755 1054 Dulles Airport 681 797 1037Frostburg, MD 377 447 609 Martinsburg, WV 715 721 985National Arboretum 994 953 1282 Reagan National 994 953 1282Salisbury 884 914 1127 St. Mary’s City 784 859 1161

To check degree day (DD) accumulations in your local area go to: http://www.weather.com/outdoors/agriculture/growing-degree-days/USMD0100

Note: degree days reported in this newsletter for various pests use the Weather.com web site, a base temperature of 50 °F, a start date of January 1st, and the date of monitoring as the end date.

June 19, 2014 – A Chance for the Horticulture Industry to Learn and Have FunTidal Creek Growers in Davidsonville will open their doors for The Maryland Greenhouse Growers’ Association and the University of Maryland Extension. This event will be both educational and good general fun. There will be competitive games organized by Ginny Rosenkranz, entertaining live music, and great food.Bring your family along to enjoy the late afternoon to evening event.

Tidal Creek Growers is a plant production greenhouse operation that is known for its production of high quality greenhouse plants. The site for the field day will feature over 5 acres of greenhouse growing area. The owner is Jake Van Wingerden and the head grower is Mike Leubecker who will lead the tours of the facilities.

The featured topic will be: What do Garden Centers Want from Greenhouse Growers?Featured Speaker: Carrie Engel, Valley View Garden Center and Nursery

For details and to register, go to http://extension.umd.edu/ipm/conferences

Stanton GillExtension Specialist

sgill@umd.edu

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

hgic.umd.edu

The information given herein is supplied with the understanding that no discrimination is intended and no endorsement by University of Maryland Extension is implied.

CONTRIBUTORS:

University of Maryland Extension programs are open to all citizens without regard to race, color, gender, disability, religion, age, sexual orientation, marital or parental status, or national origin.

Thank you to the Maryland Arborist Association, the Landscape Contractors Association of MD, D.C. and VA, the Maryland Nursery and Landscape Association, 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.

Upcoming ConferencesProcrastinators’ Pesticide Applicators Program - Eastern ShoreJune 13, 2014Location: Wye Research and Education Center, Queenstown, MDContact: Ginny Rosenkranz, 410-849-6141, rosnkrnz@umd.edu

MGGA Field DayJune 19, 2014 (afternoon through early evening)Location: Tidal Creek Growers, Davidsonville, MD

MNLA Field DayJune 26, 2014Location: Roseland Nurseries, Sudlersville, MD

Maryland Christmas Tree Association Summer MeetingJune 28, 2014Location: Gaver Tree Farm, 5501 Detrick Road, Mt. Airy, MD 21771Contact:301-865-3515 or gavertreefarm@aol.com

Greenhouse Biocontrol ConferenceAugust 6, 2014 Location: Maritime Institute, Linthicum, MD

Stormwater Management ProgramAugust 20 and 21, 2014

TWO Locations: August 20 - Montgomery County Extension Office, Derwood, MDAugust 21 - Robinson Nature Center, Columbia, MD