TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers Commercial Horticulture June 8, 2012 In This Issue... - Japanese maple scale - Recent rain - Impatiens downy mildew - European fruit lecanium scale - Lecanium scale - Brown marmorated stink bug - Rhododendron borer - Oriental beetles - Japanese beetles - Southern red mites - Flea beetles - Fall webworm - Pear blister mite - Leyland cypress yellowing - White pine weevil - Leafhoppers Beneficial of the Week Weed of the Week Plant of the Week Degree Days Phenology Conferences Coordinator 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 Brian Clark (Extension Educator, Prince George s County) Disease 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) Japanese Maple Scale Update As of Wednesday, June 6th our monitoring of Japanese maple scale (JMS) in College Park found ~33% of the scales still had eggs, ~56% were newly hatched 1st instars (=crawlers) and settled 1st instars. Another 13% were not quite 2nd instars yet. Weather.com reports 1282 DD in College Park (Jan. 1st June 6th). In Adamstown, MD on Wednesday they were at 975 DD (weather.com) and there were crawlers and settled crawlers active on trees. Based on our research and observations if the DD accumulations in your area are between 900 and 1150 DD I recommend you put on control applications of an IGR (Distance or Talus) to target crawlers of JMS. Since crawlers are active throughout the area, now is the time to treat for this scale. Integrated Pest Management for Commercial Horticulture www.ipmnet.umd.edu 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 See the earlier IPM Alert (May 18, 2012) for more information on monitoring and control recommendations at: http://ipmnet.umd.edu/landscape/lndscpalerts/2012/12may18l.pdf; and the UME Japanese maple scale fact sheet at: http://ipmnet.umd.edu/nursery/docs/japanesemaplescale-umd.pdf The questions still remain as to: how many pesticide applications and when should they be put down for optimal JMS control; and what are the pesticide options. We (the UME IPM team) are currently conducting research to answer these questions. By next season we should be able to provide this information.
Rain Last week on Friday, Central Maryland was drenched with rain. The storm rampaged through Frederick, Montgomery, Carroll, and Prince George s counties, with high winds and driving rain. Southern Maryland was basically not affected by this rain event. This rain is helping to make up for the deficit we suffered back in April, but we are still below normal rainfall for the year. Impatiens Downy Mildew We first wrote about an outbreak of impatiens downy mildew in the Greenhouse IPM Report back in February, and this week we received our first sample with the disease in the UMD Plant Diagnostic Lab. Impatiens downy mildew, caused by the fungus-like microorganism Plasmopara obducens, is favored by cool, moist conditions. The disease affects both seed and cutting propagated Impatiens walleriana, but New Guinea impatiens are resistant or tolerant. Symptoms can be very subtle, starting as a slight light green mottling or stippling on one or a few leaves. Infected leaves may curl downward. If you look at the undersides of these leaves, the white fuzzy growth of the pathogen is visible. As the disease progresses, infected plants will be stunted, and leaves and flowers fall leaving bare, leafless green stems. The disease can cause severe losses in both greenhouse production and landscape plantings. Thick-walled oospores produced in infected leaves and stems can overwinter in soil and be a source of the disease in following years. Slight mottle and leaf curl symptoms of downy mildew on impatiens Photo: Karen Rane, UMD Underside of leaf, note white fuzzy sporulation Photo: Karen Rane, UMD There are several fungicides that can protect plants from downy mildew infection, but they must be applied preventatively. Unfortunately, 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. We really would like to know the extent of this disease in our region. 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) so we can arrange to get samples. Check out the American Floral Close-up of sporulation of Plasmopara Endowment website for an excellent collection of articles, fact sheets obduscens on the underside of an and fungicide recommendations for both greenhouse growers and impatiens leaf. Photo: Karen Rane, UMD. landscapers. (http://www.endowment.org/afe-news/press-releases/221-controlling-downy-mildew-on-impatiens.html) 2
European Fruit Lecanium Scale, Parthenolecanium corni This week, European fruit lecanium scale is producing crawlers which are white and then turn yellow. Look for this scale on flowering fruit trees, maples and many other woody plants in the landscape and nursery. Females are about 1/4 inch long and color varies according to hosts, from reddish brown to brown with black markings. One generation is produced each year. Immatures overwinter on bark. Biological Control: European fruit lecanium scale is attacked by several species of parasites, including Aphytis spp., Coccophagus spp., Encarsia spp., and Metaphycus luteolus. Common predators that help control this scale include lady bird beetles (Chilocorus European fruit lecanium scale orbus, Hyperaspis spp., Rhyzobius lophanthae), lacewings, the predaceous sap beetle (Cybocephalus californicus) and predatory seed bugs (Phytocoris spp.) Chemical control: Since they have so many predators and parasites, it is best to use an IGR (Insect Growth Regulator) to control this scale, using materials such as Talus or Distance. The crawler stage is the stage most susceptible to chemical treatment, especially when using summer oil sprays. Crawlers emerge for a period of about 6 weeks. Treatment levels for scale have not been established. Determine the need for treatment of European fruit lecanium by evaluating records of honeydew from the previous season. Time treatment by monitoring for crawlers and turning over females to note if crawlers are present among the eggs. Other treatments include imidacloprid and dinotefuran. Lecanium Scale Marty Adams brought a bald cypress sample by the office on June 1 that has an infestation of a lecanium scale. The sample had both eggs and crawlers present. Craig Greco, Yardbirds, Inc., is also finding lecanium scale on hawthorn. Control: Talus or Distance with 0.5% horticultural oil would give good control at this point. Brown Marmorated Stink Bugs We are receiving reports of eggs and egg hatch of brown marmorated stink bugs from both Southern Maryland and Central Maryland. So far, it appears that numbers are lower this year compared to the past few years. Look for them on the underside of foliage. We are once again surveying to determine the BMSB populations so please let me (Stanton - sgill@umd.ed) know if and where you are finding eggs and nymphs and whether the population seems lower, higher, or about the same in your area. Rhododendron Borer On June 3, the first adult rhododendron borer was caught in a baited pheromone trap in the Westminster area. This clearwing moth borer generally attacks weakened rhododendrons. There is one generation a year and larvae overwinter in tunnels in branches. Look for wilting leaves and dieback. Prune off suspect branches and dissect them longitudinally to see if larvae are present. Control: Susceptible plants can be treated using Permethrin or Bifenthrin applied to the trunks. 3
Oriental Beetles We received a report of adult activity from Kerry Wixted, DNR. She found an oriental beetle which is a scarab beetle on a marigold in Crownsville. It was the only one she has seen so far this season. Adults can cause some damage to flowers, but flower damage is usually not significant. Oriental beetle adult Photo: Kerry Wixted, DNR Japanese Beetles Japanese beetle is another scarab beetle that is starting to become active this week which is earlier than usual. Matt Katsuleres spotted one Japanese beetle on June 1 at the UMD turf farm in Beltsville. He noted that it was crawling on false indigo. Dave Clement, HGIC, also found them causing injury on London plane trees in Prince Frederick on June 8. David Kinderdine, Velvet Touch Rose Care, reported a major outbreak of beetles in Bethesda on June 8. There are red, yellow and pink Knockout roses planted in the landscape and the yellow ones are receiving the most damage. Control: Adult Japanese beetles can be controlled by several insecticides (ex. clothianidin [Arena], imidacloprid). If grub control is warranted in turfgrass many of the neonicotinoids are labeled and give good control such as imidacloprid, clothianidin, and thiamethoxam. Acelepryn is a newer product that has shown very good control of grubs. Southern Red Mite Southern red mites were reported to be very active on cherry laurels in Howard County and Prince Frederick. The cherry laurels in these cases are planted at the base of a building or near a house. The plants are loaded with these spider mites. The foliage shows extensive stippling and there is webbing on plants. Monitoring: Look for red eggs that overwinter on the undersides of foliage and twigs of Japanese hollies, cherry laurel, camellia, and azalea. A tap test over white paper can show whether mites are present on the plant. Also look for signs of stippling and webbing on the foliage. Control: Horticultural oil, Hexygon, Floramite, Akari, or other labeled miticides. Heavy mite damage on holly Flea Beetle Flea beetle activity is just starting on Hibiscus moscheutos plants in Ellicott City this week. Look for adult flea beetles on the upper sides of foliage and shothole damage to foliage. Control: Mature plants should recover from damage and control is not usually warranted. Applications of Azatin can be used to reduce flea beetle populations. 4
Fall Webworm Tony Murdock, Fine Pruning, sent in a sample of Japanese honeysuckle with a heavy infestation of the first generation of fall webworm. The sample was collected from Thurmont on June 1. Fall webworm has a wide host plant range. The larvae feed within the webbing they produce. Control: Bt, horticultural oil or insecticidal soap for early instars or prune out webbed branches. There are many predators and parasites that help keep this pest below damaging levels. Early instar fall webworm, fecal droppings and heavy webbing Pear Blister Mite Damian Varga, Plant Scientific Service, found pear blister mite on callery pear in Ellicott City on June 5. This mite causes brownish blisters on the undersides of pear and apple leaves. The pimple-like blisters start greenish and become red before finally turning brown on pears. The blisters on apples start yellow and never become as red as the ones found on pears. When massed together, these blisters can cover large areas of the undersides of leaves. Look at the undersides of leaves for the blister-like galls in the spring. Control: If necessary, treat in the fall before leaf drop to control females before they overwinter. Blistering on underside of foliage Leyland Cypress Yellowing The Home and Garden Information Center is getting several inquiries on Leyland cypress with interior foliage turning yellow. When needles reach 3 years old on Leyland cypress there is a maturing of the old growth and yellowing, then browning and eventual dropping of the old foliage. Nothing is wrong with the plants. White Pine Weevil A grower sent in a photo of a white pine weevil larva that was found in a blue spruce. With this weevil, as the hatching larvae feed you will see flagging of terminal growth in late July through August. Control: If you are going to apply a chemical control, then now is the time. A synthetic pyrethroid such as bifentrhin (Talstar) or permetrhin (Onyx) will provide control. White pine weevil Photo submitted by a grower Leafhoppers A grower mentioned this week that he is finding that leafhoppers are the worse he has ever seen them and that he has seen them on trees that usually do not get them, such as oaks and hornbeams. 5
Beneficial of the Week, Paula Shrewsbury Emerald ash borer larvae: Who eats them? Earlier this year (April 27th report) when emerald ash borer (EAB) adult beetles started their activity, which included feeding, mating and laying eggs, I discussed a small parasitic wasp, Oobius agrili (Encyrtidae), which parasitizes the eggs of emerald ash borer (EAB). EAB adult beetles have been active for several weeks and their larvae are now busy feeding under the bark on the cambium tissue of ash trees. As most of you know EAB is an exotic (native to Asia) and invasive flat headed beetle that has killed millions of ash trees and cost municipalities and states extraordinary amounts of money. As part of our defense against EAB, parasitic wasps from Asia have been brought back to the U.S. and after extensive studies in quarantine, some species are being released in the environment. To date 3 parasitoids (very tiny wasps) from Asia are being released in several states that have EAB, including MD. Since EAB larvae are now active I would like to discuss one of the introduced larval parasitiods, Spathius agrili (Braconidae). In China, Spathius was found parasitizing up to 90% of EAB larvae in trees. Spathius is a gregarious ectoparasitoid of EAB larvae. This means that multiple parasitoid individuals feed on one EAB larva (gregarious) and that they feed from the outside (ecto) vs inside (endo) of the larval body. Adult female Spathius have been observed tapping the bark with their antennae as they search for EAB larvae. Once a larva is found, Spathius use their relatively long ovipositors (~2mm) to drill through the bark of ash where the EAB larva resides underneath. The wasp pierces the EAB larva and paralyzes it with its venom. It then will lay up to 23 eggs on the body surface of one larval host. The hatching parasitoid larvae feed gregariously on hemolymph (blood) of the EAB larva - which ultimately results in the EAB larva s death. Spathius has multiple generations per year so this cycle is repeated 3-4 times each summer and fall. Spathius overwinter as pupae inside cocoons in the EAB galleries under the bark of ash trees. The next summer, Spathius completes its development to adulthood, chews a hole in the bark of the tree from which it emerges and starts the cycle all over again. If successful, this classical biological control approach should provide long-term, sustainable management of EAB. A Spathius agrili parasitic wasp adult. Note the long ovipositor for inserting through the bark of ash trees to reach EAB larvae. Photo: Stephen Ausmus, USDA Science Photo Library Several Spathius agrili larvae feed from the outside on an EAB larvae. Photo courtesy of Dr. Yang Zhongqi, Chinese Academy of Forestry Weed of the Week, Chuck Schuster Giant hogweed, Heracleum mantegazzianum, is a noxious weed that is listed on the federal noxious weed list. This plant can grow to heights of twelve to fifteen feet. Do not touch the sap of this plant as it can harm you. Hogweed has a biennial life cycle, though it can live for several years as a rosette, when it produces seed (up to 20,000) it will die. It produces a dense taproot. It was brought in to the United States in the early 1900 s from Europe as an ornamental plant. It has a hollow stem with white hairs at the nodes and the base of the petiole. 6
The stem is green with purple blotches. It produces a cluster of small white flowers that is similar in shape to that of an umbrella. Control of giant hogweed needs to start with caution. The sap on your skin, when exposed to light, can cause extensive skin burns. It can be cut down or dug up. Use of triclopyr and glyphosate have been very effective, while 2,4-D and combination products are only effective at damaging the top growth but not effective at killing the roots. Close-up of giant hogweed leaf Photo: Marty Adams, Bartlett Tree Experts Giant hogweed in bloom Barbara Tokarska-Guzik, University of Silesia, Bugwood.org Plant of the Week, Ginny Rosenkranz Lavender angustifolia, English lavender, can be used in landscape settings as an addition to a perennial border, in a foundation planting, as a formal or informal edging along paths, raised beds, in drifts and in herb gardens. English lavender is an evergreen herbaceous perennial that blooms with fragrant clouds of blue purple flowers (some varieties can be white or pink). It can be harvested for potpourris, sachets and even as edible flowers. The foliage is grey green in the summer months, silver green in the cold of winter and is aromatic when you brush against it. Lavender plants can grow 24-36 inches and spread 36-40 inches if planted in full sun with excellent soil drainage, especially in the winter months. Sandy soils and sandy loams with a neutral ph is preferred, and many herb gardens are mulched with gravel to reduce the amount of moisture retained compared to wood bark 7 Lavender in bloom and butterlies Photo: Ginny Rosenkranz, UME mulch. Watering when first established in the summer will promote deep root growth, allowing better winter protection. The plants are cold hardy from USDA zones 5-7. Both Munstead (12 inches) and Hidcote (15-20 inches) are compact plants that grow slowly, allowing landscape contractors to utilize them as edging plants. Pruning lavender plants after blooming will encourage new growth and maintain the compact habit of growth. Pests include rabbits, slugs, snails and sometimes spittlebugs. Diseases include alfalfa mosaic virus. Cold wet soils in the winter will kill the plants.
Degree Days (As of June 7)* Baltimore, MD (BWI) 1085 Dulles Airport 1066 Frostburg, MD 623 Martinsburg, WV 1011 National Arboretum 1317 Reagan National 1317 Salisbury 1153 *As of May 11, degree day calculations are from weather.com growing degree day calculations instead of NOAA min and max temperatures. To check degree day (DD) accumulations in your local area go to: http://www.weather.com/outdoors/agriculture/growing-degree-days/usmd0100 Plant Phenology: What s in bloom PLANT PLANT STAGE (Bud with color, First LOCATION bloom, Full bloom, First leaf) Asclepias tuberosa Full bloom (June 7) Ellicott City Ascelpias incarnata Full bloom (June 8) Ellicott City Stewartia pseudocamellia Full bloom (June 5) Ellicott City Yucca filamentosa Golden Sword First bloom (June 5) Ellicott City 8
Upcoming Programs MNLA Field Day June 21, 2012 Location: D.R. Snell Nursery, Union Bridge, MD http://mnlaonline.org/ Maryland Christmas Tree Association s Summer Meeting June 30, 2012 (Saturday) Location: Taylor Sines Woodlake Tree Farm, Oakland, MD Contact: 410-452-9793 OFA Perennial Production Conference September 10-12, 2012 Location: Grand Rapids, Michigan ofa.org IPPS Eastern Region Annual Meeting October 10-13, 2012 Location: Brandywine Valley, Pennsylvania http://www.ippseastern.com 2012 Perennial Plant Symposium July 4-10, 2012 Location: Boston, Massachusetts perennialplant.org OFA Short Course July 14-17, 2012 Location: Columbus, Ohio ofa.org PANTS 2012 (Pennsylvania Nursery Trade Show) July 31 to August 2, 2012 Location: Greater Philadelphia Expo Center, Oaks, PA www.pantshow.com/2012 CONTRIBUTORS: Stanton Gill Extension Specialist sgill@umd.edu Paula Shrewsbury Extension Specialist pshrewsb@umd.edu Karen Rane Plant Pathologist rane@umd.edu Chuck Schuster Extension Educator cfs@umd.edu Ginny Rosenkranz Extension Educator rosenkrnz@umd.edu David Clement Plant Pathologist hgic.umd.edu Andrew Ristvey Extension Specialist aristvey@umd.edu Brian Clark Extension Educator bpclark@umd.edu 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. The information given herein is supplied with the understanding that no discrimination is intended and no endorsement by University of Maryland Extension is implied. 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.