for Arborists, Landscape Managers & Nursery Managers

Commercial Horticulture September 4, 2015Coordinator Weekly IPM Report: Stanton Gill, Extension Specialist, IPM for Nursery, Greenhouse and Managed Landscapes, sgill@umd.edu. 301-596-9413 (office) or 410-868-9400 (cell)

Regular Contributors: Pest and Beneficial Insect Information: Stanton Gill and Paula Shrewsbury (Extension Specialists) and Nancy Harding, Faculty Research AssistantDisease Information: Karen Rane (Plant Pathologist) and David Clement (Extension Specialist)Weed of the Week: Chuck Schuster (Extension Educator, Montgomery County)Cultural Information: Ginny Rosenkranz (Extension Educator, Wicomico/Worcester/Somerset Counties)Fertility Management: Andrew Ristvey (Extension Specialist, Wye Research & Education Center)Design, Layout and Editing: Suzanne Klick (Technician, CMREC)

In This Issue...

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

plant problems found in the landscape or nursery to

sklick@umd.edu

TPM/IPM Weekly Report

- Weather update- Hands-on program- Caterpillars- Tuliptree scale- Tupelo leafminer- Testing for nematodes- Wheel bugs

Beneficial of the WeekWeed of the WeekPlant of the WeekPhenologyDegree DaysAnnouncements

IPMnetIntegrated Pest Management for

Commercial Horticulture

extension.umd.edu/ipm

How Dry Is It?By: Stanton Gill, University of Maryland ExtensionAfter a very wet June and July in the Northeast, rains have been spotty. Here is what the USA.gov weather prediction is: “Very dry and warm weather during the past 30 days in the southern Plains, lower Mississippi Valley, Great Lakes region, and Northeast have developed or expanded short-term abnormal dryness and drought, especially from the southern Great Plains eastward into the Carolinas. September precipitation odds favor sub-median rainfall along the eastern Gulf and southern Atlantic Coast States, along with above-normal temperatures. Since October and November are climatologically drier than September, and an enhanced sub-tropical jet would most-likely favor areas farther to the west.”

Jerry Faulring, Waverly Farm, sent in this interesting data he has been collecting at his nursery:

I have been keeping daily rainfall amounts here for 18 years. The following are some interesting data for 2015 and averages:

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Diagnosing Problem on Herbaceous Perennials On September 16, Stanton Gill, Karen Rane, David Clement, and Mary Kay Malinoski will be conducting a seminar on diagnosing problems with herbaceous perennials. You can register for this seminar at the LCA website and obtain the schedule for the day. We plan to have a hands-on section to the seminar, so we welcome you to bring samples to the seminar.

Caterpillars Out in Early SeptemberBy: Stanton Gill, University of Maryland ExtensionI am receiving e-mails from Baltimore County, Harford, Montgomery, Prince George’s, Washington and Carroll counties reporting a lot of activity from the orange-striped oakworm caterpillar. The caterpillars are finishing up feeding on oak foliage as we move into September. The late instar larvae are being found wandering about landscapes looking for places to pupate. This “wandering about” is making them very visible to landscape managers customers. Nothing is necessary to do for this caterpillar, especially this late in the year.

On Sunday I had an eight year old girl, Juliet, show up at our farm market in Olney. She had a big smile and a large jar full of caterpillars. She proudly dumped these out on one of our tables. They were red-humped caterpillars, Schizura concinna, that she had patiently pulled off her parents’ blueberry bush, one by one. Red-humped caterpillars are found throughout the summer and a lot in late summer, feeding gregariously in large clusters. Their defoliation of a plant this late in the season is not going to damage the health of the plant since it had all season to produce food. Control is not necessary for this pest in September. As for Juliet, I hope she keeps her interest in entomology.

June: The total was 10.56” compared to average of 4.00” and YTD was 22.97 vs 19.39 average so annual totals are close.

July: The total was .92” compared to average of 3.16” and YTD is 23.89 vs 22.64 so annual average was close. August: The total was 2.15” so far (mid-August) compared to average of 2.63” and YTD is 26.04 vs 25.41 so annual average is close.

We had 3” in the last 8 days of June which lulled us into thinking July was wet, in fact the June rain kept us going for a while in early July. August isn’t over but the 10 day forecast shows one possible rain event. My experience for July and August is that 3 or 4 inches doesn’t make a world of difference because it usually blows away in a few days.

It looks like we are in for dry periods through this end of the summer into early fall.

Orange-striped oakworms are starting to look for places to pupate

Red-humped caterpillars have a wide woody plant host range

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Tuliptree Scale on Deciduous MagnoliaBy: Stanton GillChristopher Ward, John B. Ward and Company, found tuliptree scale crawlers in Bryn Mawr, PA, just west of Philadelphia, PA this week. There was a heavy infestation of tuliptree scale, Toumeyella liriodendri on deciduous magnolia. The females still have plenty of eggs under the covers, so it appears the crawler stage has just started. This scale excretes copious amounts of honeydew that cover the foliage and stems of magnolia. Sooty mold grows on the honeydew and gives the foliage and stems a powdery black cast. Control options: Distance or Talus IGRs can be applied or a basal trunk drench of dinotefuran would work.

Look for the blotch mines from feeding of tupelo leafminer on black tupelo

Tupelo LeafminerIn 2007, we started getting reports of heavy damage to black tupelo which turned out to be feeding activity of tupelo leafminers. These leafminers are very small caterpillars. It’s been about 5 years since we had a report of them. We found mostly old damage on September 1 on trees along the edge of the woods here at the research center. Most have finished feeding and pupated – note the distinct holes at the edge of the blotch mines. They cut a hole in the leaf and produce silk to secure themselves within the upper and lower leaf layers before dropping to the ground. Rake up the leaves to remove many of the overwintering cocoons to help reduce next year’s population.

Look for reddish crawlers emerging from under the covers of tuliptree scale females

The leafmining caterpillar can be seen within the blotch mine in the leaf

The distinct holes indicate that the larvae have dropped to the ground to pupate

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Wheel BugJessica Frakes. Thrive, Inc., found this wheel bug active in Potomac this week. Wheel bugs are generalist predators found throught the spring and summer in landsapes. As we move into fall the adults will be laying eggs in clusters on small branches of woody plants.

Saprophytic fungi feed on dead organic material and are harmlessPhoto: Harold Wollman, Chapel Valley Landscape

Fungi on MulchHarold Wollman, Chapel Valley Landscape, found saprophytic fungi growing on a mulched area that was irrigated. It is harmless. The fungus breaks down mulch. The warm weather combined with the irrigation makes perfect conditions for the fungus to grow.

Where to Send Samples for Nematode TestingBy: Karen Rane, University of Maryland ExtensionThis message is to inform you all that the University of Delaware no longer accepts out of state soil samples for nematode testing. There are other university-affiliated nematology labs that will accept out of state samples for nematode testing - three are listed below. Sample submission information, fees and addresses can be found at the websites for each lab. Virginia Tech Nematology Laboratory (phone 540-231-4650) https://www.ppws.vt.edu/extension/nematode-laboratory/index.html Clemson Plant Problem Clinic and Nematode Assay Lab http://www.clemson.edu/public/regulatory/plant_industry/pest_nursery_programs/plant_prob_clinic/ Rutgers Plant Diagnostic Laboratory and Nematode Detection Service https://njaes.rutgers.edu/plantdiagnosticlab/

Wheel bugs will be laying eggs as we move into fall; egg hatch will be next spring (usually about early May)Photo: Jessica Frakes, Thrive, Inc.

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Nimblewill is tolerant to shade and sun Photo: Virginia Tech Weed ID Guide

Beneficial of the WeekBy: Paula Shrewsbury, University of Maryland

Not all thrips are bad thrips

When we hear of thrips (Thysanoptera) we often think of insects that damage plants. Fortunately, not all thrips are bad thrips. In addition to plant feeding or phytophagous thrips, there are also several species of predaceous thrips. Unfortunately, predaceous thrips look a lot like plant feeding thrips, especially in their size (both very small) and shape. Thrips are small (<1/8”, 2-3 mm in length), elongate insects. Adult thrips have wings that are thin with long fringes of hair on the margins, while immature thrips look similar but lack developed wings. Thrips have multiple generations per year.

Predatory thrips, both adults and immatures, eat other plant feeding thrips, spider mites, lace bugs, whiteflies, scales, and eggs of insects. They forage or hunt on the foliage, buds, and flowers of many plants. One of the more common species of predacious thrips we have around here is sixspotted thrips, Scolothrips sexmaculatus. Adults are pale yellow and can be distinguished from other species by the three dark spots on each wing cover. Nymphs are translucent white to yellow and difficult to discriminate from other thrips species. Sixspotted thrips can reduce high mite populations, but often do not become numerous until mite densities are high and damage can be seen. Other species of predatory thrips include banded thrips (Aeolothrips fasciatus) and black hunter thrips (Leptothrips mali). The following link provides excellent images of predatory thrips (http://www.ipm.ucdavis.edu/PMG/C008/m008bppredthrips.html).

Predatory thrips are sensitive to pesticides. Careful selection and reduced use of insecticides can help to conserve populations of these good thrips and allow them to keep providing biological control of many common pests on our ornamental plants.

A predaceous sixspotted thrips feeding on a spider mite. Note the six dark spots on the wingsPhoto: Jack Kelly, UC

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

Nimblewill (Muhlenbergia shreberi) is a warm season perennial grass. This grassy weed is often mistaken for Bermuda grass; it has a similar growth pattern and will become dormant in the fall. It reproduces through seed and short stolons and will root at nodes. The blue-green short leaves are up to two inches long. Nimblewill produces a long slender flower stalk in late summer. It is tolerant to sun and shade, liking shade more, and prefers moist growing conditions. Nimblewill differs from Bermuda grass; only Bermuda grass has rhizomes. Nimblewill has a narrower leaf blade and is wirier than Bermuda grass. It does not tolerate cold temperatures and turns brown leaving a brown patch in fall and winter as does Bermuda grass.

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Control can be done culturally by maintaining a dense healthy turf, mowing at an appropriate height for the desired turf, increasing drainage of the site and maintaining proper soil fertility. Do not allow nimblewill to go to seed; if seed is present, collect grass clippings. Chemical control is difficult and usually requires the use of non selective herbicides (glyphosate) when the plant is actively growing and then reseeding the site. Recent work has shown promise with the use of use of Tenacity for nimblewill control in residential lawns.

Plant of the WeekBy: Ginny Rosenkranz, University of Maryland ExtensionIlex opaca ‘Maryland Dwarf’ is a dwarf spreading female cultivar of the native American holly and only grows 3 feet tall but spreads up to 10 feet wide. The oval-shaped evergreen foliage is dark green and glossy with spines along the outside edge. In the spring ‘Maryland Dwarf’ is covered in fragrant green-white flowers that mature into bright red berries that persist through the chilly winter weather. I. opaca ‘Maryland Dwarf’ is a female and will need at least one male holly nearby for better pollination and a richer set of berries. A slow growing plant, ‘Maryland Dwarf’ grows best in full sun to partial shade, with acidic, rich moist soils. It is very tolerant of a broad range of soil conditions from clay to sandy, but prefers to grow on the edges of streams and ponds and not in them. Like all the native American hollies, ‘Maryland Dwarf’ needs some winter protection from the frigid north west winds and is cold hardy from USDA zone 5-9. Birds are very attracted to the bright red berries at the end of winter and early spring, but deer usually leave I. opaca ‘Maryland Dwarf’ alone. The branches can be brittle so care should be taken when pruning or weeding around the dwarf tree. ‘Maryland Dwarf’ can be used as a low, slow growing evergreen hedge, as a groundcover, in woodland gardens or in a bird garden. Pests include holly leafminer, spider mites, whitefly, scale, leaf spot, leaf scorch and chlorosis if the plants are grown in soils with a high pH.

Ilex opaca ‘Maryland Dwarf’ is slow growing and reaches about 3 feet in heightPhotos: Ginny Rosenkranz, UME

Degree Days (As of September 3) 2015 2014 2013 2015 2014 2013Baltimore, MD (BWI) 3234 2939 3107 Dulles Airport 3184 2800 3113Frostburg, MD 2222 1884 1984 Martinsburg, WV 3014 2828 2880 National Arboretum 3911 3585 3536 Reagan National 3911 3585 3536Salisbury 3163 3225 3399 St. Mary’s City 3278 3044 3232

To check degree day (DD) accumulations in your local area go to: http://www.yourweekendview.com/outlook/agriculture/growing-degree-days/. Note: degree days reported in this newsletter use a base temperature of 50 °F, a start date

of January 1st, and the date of monitoring as the end date.

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

CONTRIBUTORS:

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

Thank you to the Maryland Arborist Association, the Landscape Contractors Association of MD, D.C. and VA, the Maryland Nursery and Landscape Association, Professional Grounds Management Society, and FALCAN for your

financial support in making these weekly reports possible.

Photos are by Suzanne Klick or Stanton Gill unless stated otherwise.

Stanton GillExtension Specialist

sgill@umd.edu410-868-9400 (cell)

Paula Shrewsbury Extension Specialistpshrewsb@umd.edu

Ginny RosenkranzExtension Educatorrosnkrnz@umd.edu

Chuck SchusterExtension Educator

cfs@umd.edu

Karen Rane Plant Pathologistrane@umd.edu

Andrew RistveyExtension Specialistaristvey@umd.edu

David ClementPlant Pathologist

clement@umd.edu

Nancy HardingFaculty Research

Assistant

Upcoming Conferences:

LCA Hands-on Training SeminarSeptember 16, 2015 Location: Johns Hopkins University, Montgomery County Campus

Interiorscape ConferenceOctober 1, 2015 Location: Rawlings Conservatory, Baltimore, MD

Community Forestry WorkshopOctober 2, 2015Location: Carroll Community College, Westminster, MDhttp://www.westgov.com/182/ForestryWorkshop

4th Annual TreesMatter SymposiumNovember 4, 2015Location: Silver Spring Civic Center, Silver Spring, MD

December 10, 2015 Pest Management Conference Details will be posted late September or early October