TPM/IPM Weekly Report

Transcription

1 TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers Commercial Horticulture May 18, 2012 In This Issue... - Oak leaf blister - Black bears - Fire blight - Cottony camellia (taxus) scale - Black vine weevil - Potato leafhopper - Juniper scale - Lace bug correction - Daylily leafminer - Azalea plant bug - Evergreen rust diseases - Spittlebugs - Japanese maple scale update - Witchhazel gall aphids - Powdery mildew on dogwood - Powdery mildew on euonymus - Frogeye leafspot on maple - Stalk borer on elderberry - Slugs - Gymnosporangium rusts Beneficial of the Week Plant of the Week Phenology Degree Days Conferences Integrated Pest Management for Commercial Horticulture 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 Coordinator Weekly IPM report: Stanton Gill, Extension Specialist, IPM for Nursery, Greenhouse and Managed Landscapes, sgill@umd.edu (office) or (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) Oak Leaf Blister During a pest walk on the Eastern Shore last week, we saw a large willow oak with an unusually severe case of oak leaf blister, caused by the fungus Taphrina caerulescens. Infection occurs in early spring as buds open, and light green, blisterlike areas develop on leaves as they expand. Spores produced on the whitish layer on the underside of the blister are washed to bark Oak leaf blister and bud scales by rainfall, Photo: Karen Rane, UME where they remain until next spring. As the growing season progresses, the blistered areas become necrotic. Control is usually not warranted for landscape oaks with leaf blister, because the impact on the health of the tree is usually minimal. In nurseries, an application of a protectant fungicide such as mancozeb prior to bud break (late dormancy) may help reduce leaf blister. Once symptoms are observed, fungicides are ineffective.

2 New Pest? In the Sugarloaf area (border of Montgomery and Frederick counties), Banner Bee Company suffered damage to 15 bee hives from black bear. DNR confirmed that it was black bear damage to the hives. It took the owners several days to clean up around some very angry bees. Fencing will be put up around the area. A black bear female and a cub were reported to be active on Penn Shop Road of Frederick. It looks like black bear is making a comeback which may create a whole new set of challenges in urban landscapes. Fire Blight We are seeing samples come in of ornamental pears and cultivated apples with fire blight symptoms on tip growth. There is nothing much to do other than prune out the damaged branches well below the canker areas on the stems. Do this pruning in dry weather. 2 Fire blight on callery pear Cottony Camellia (Taxus) Scale Kevin Nickle, ProLawn Plus, Inc., brought in a holly sample with a heavy infestation of cottony camellia scale. Other hosts include yews, camellia, rhododendron, Japanese maple, and mulberry. A few crawlers were found on this sample, but most were still in the egg stage. Look for yellowing of foliage and plant dieback in severe infestations. This soft scale produces large amounts of honeydew on which sooty mold will grow. The scale tends to accumulate on the undersides of foliage. There is one generation a year, but each female can produce over 1000 eggs so populations can build up quickly. Control: Wait for eggs to hatch and then treat with pyriproxyfen (Distance) or buprofezin (Talus) mixed with 0.5-1% horticultural oil. Soil injections of imidacloprid (Merit in the landscape, Marathon in nurseries) can be applied in April. Cottony camellia scale on holly Black Vine Weevil (Otiorhynchus sulcatus) We received the first sample of adult black vine weevil this week. Adults are out and feeding at night on foliage of herbaceous perennials. The black vine weevil is a pest of over 100 landscape plants. The adults feed on a wide variety of evergreen, deciduous, and herbaceous plants. The black vine weevil is also destructive in the larval form on yew (Taxus spp.), hemlock, rhododendron, and several other evergreens. A Black vine weevil adult Photo: Cheryl Moorehead, Bugwood.org Black vine weevil larva fact sheet, which includes herbaceous perennials most likely to be damaged by this pest and control options, is available at

3 Potato Leafhopper The first adult potato leafhoppers were reported in the Westminster area on May 11 on red maple. Potato lefhopper feeding causes the tip growth on maples to curl over and harden which is typically referred to as hopperburn. The multiple generations keep damaging the new tip growth that flushes out on the maples. The leafhoppers migrate from the south and feed on new growth. Females will lay eggs on tip growth and the nymphs will be feeding in the next couple of weeks. Control: Applications as soils drenches include Thiamethoxam (Flagship), Imidacloprid (Marathon and other trade names now that the patent has expired), Dinotefuran (Safari), and Cyfluthrin (Discus). You Potato leafhopper can also make foliar applications of Acephate (Orthene) but this would Photo: Frank Peairs, Colorado State have to be repeated for the multiple generations that occur over the University, Bugwood.org summer. Acetamiprid (Tristar), Discus and Kontos can also be applied as a foliar spray in nursery beds. Juniper Scale Crawlers are Out Juniper Scale, Carulaspis juniperi (Bouche), an introduced pest of European origin, is in the crawler stage this week in central Maryland and on the Eastern Shore. The ornamental junipers most commonly attacked are red cedars, Juniperus virginiana, Irish juniper, J. hibernica, Savin juniper, J. sabina and Pfitzer juniper, J. chinensis Pfitzeriana. Juniper scale will also attack cypress, Cupressus ssp., falsecypress, Chamaecyparis Female juniper scale Photo: U.S. National Collection of Scale Insects Photographs Archive, USDA Agric. Research Service, Bugwood.org ssp., and incense cedar, Calocedrus decurrens. The adult female scale is 1/16-1/20 in diameter and white with a central yellow spot which makes it resemble a miniature fried egg. Male scales are smaller with a more elongated appearance and a yellow spot on one end. Newly hatched crawlers are bright yellow, but soon fade to a tan color before forming their white waxy covering. To check for the crawlers that are usually on the undersides of foliage, tap an infested twig over a piece of white paper. Control: The larval and adult stages of dustywings and lady bird beetles are common predators of juniper scale, and several species of parasitic wasps help control this pest. If beneficial predators are present, predator friendly insecticides such as Distance, Talus, insecticidal soap or horticultural oils should be used. 3 Male juniper scale Correction from May 11, 2012 IPM Report - Pieris Lace Bug Several people pointed out that we incorrectly identified the photo in the May 11th report as azalea lace bug, when it was actually pieris lace bug on pieris. The life cycles are very similar and control is the same. Daylily Leafminer Gaye Williams, MDA, observed many adults of daylily leafminer, Ophiomyia kwansonis, on daylily plants throughout a large garden in Davidsonville on May 11. These are the first adults seen in several weekly inspections of this site. Mining should start shortly. The September 30, 2011 has details of this relatively new insect for Maryland at

4 Azalea Plant Bug Colin Stewart, USDA, reported the activity of this predator several weeks ago. This week, Bill Miller, The Azalea Works, found both juvenile and adult stages of this plant bug on Rhododendron atlanticum. He commented that it s a little red bug with an out-of-proportion (big) bite. Azalea plant bug - nymph (left) and adult (right) Photos: Bill Miller, The Azalea Works Evergreen Rust Diseases Dave Keane, Howard County Recreation and Parks, is finding pine needle rust on loblolly pine in Columbia this week. Last week, David Clement, HGIC, found it at a site in Montgomery County. Most evergreen rust diseases are easily visible as yellowish-orange spots or lesions located either on needles or branches. These spots are typically filled with powdery spores of the same color, which are spread by wind. The life cycles of these fungal rust pathogens are usually complex and in most cases these fungi cannot spread from evergreen to evergreen but involve a secondary or alternate host plant. All species of pines, spruces, hemlocks, cedars (junipers), Douglas fir and true firs are susceptible to one or more species of needle rust. Depending on the rust species these fungi Pine needle rust Photo: David Clement, HGIC can also cause growths or galls along the stems and a proliferation of side shoots typically called a witches broom. Pine needle rust infects pine needles and forms small pustules on the needles filled with yellowish to orange spores. The alternate hosts for pine needle rust are asters and goldenrod. Management strategies for these rust diseases involve separating alternate hosts by a distance of one to two miles (when practical), and the use of resistant varieties. Fungicides are often not effective control options. Spittlebugs David Barlyski found nymphs of the pine spittlebug, Aphrophora parallela, on white pine on May 17 in Clarksville. This native spittlebug also feeds on Austrian pine, firs, spruce, and Scots pine. The overwintering eggs (on the bark of the tree) are just starting to hatch. The nymphs feed on plant sap from under frothy, spittlelike foam which protects them from predators, parasites and dry weather. Monitoring: In May the frothy spittle is forming around the nymphs, usually found on terminal growth of spruces or pines. Control: Usually not necessary for this pest. This pest has a wide range of natural enemies. Spittlebug on pine Photo: Rondalyn Reeser 4

5 Japanese Maple Scale Update Crawlers are JUST starting to become active on maples in College Park, MD. When monitoring Japanese maple scale (JMS) we flip the wax covers of a known number of JMS. As of Tuesday, May 15th we found ~92% of scales had eggs, 1% had no eggs, and 7% had crawlers hatching. The degree day monitor we have on campus reported 780 DD (Jan. 1st May 14th). Weather.com reports 777 DD in College Park for the same time period. Data based on 3 years of JMS studies indicate 1st generation crawler activity should start around 815 DD (base 50 F, start date Jan. 1) pretty accurate based on this year s activity. Looking at samples from Montgomery and Frederick counties, we found females and a few covers with eggs underneath, but so far no crawlers found in these locations. JMS is a challenging pest to manage and it will take an asserted effort to control it. Below are management recommendations based on the fact that DD are guidelines that tell you when you should be more intensely monitoring your insects and plants, that areas of MD vary in temperature and therefore may or may not have crawler activity yet, and what we know about the JMS lifecycle and chemicals that suppress it. Monitoring: Go to weather.com and check the Degree Day (DD) accumulations (see last week s report for how to do this) for your location. If DD are close (with ~50 DD) to 815 DD monitor JMS host plants for crawler activity. See newly emerged crawler and settled crawler images so you know what you are looking for. Check multiple plants. You will need some type of magnifier (20x minimum). Note: Our studies have found first generation crawler activity lasts about 7-8 weeks. Since commonly used insect growth regulators (IGR) only have 2-3 week residual activity multiple applications may be necessary. Given the long crawler activity period I recommend waiting to apply your first IGR application until just before PEAK crawler activity (vs. when you see the first crawlers). Research indicates PEAK 1st generation crawler activity occurs around 1150 DD. Management: Target PEAK crawler activity with an IGR such as buprofezin (Talus) or pyriproxyfen (Distance) in nurseries or landscapes. A second or even 3rd application may be necessary. Read labels regarding rotation of active ingredients and use limits. Spirotetramat (Kontos), a systemic insecticide, was shown to have some control of JMS in a research trial (Gill et al. 2010). In landscapes, a systemic insecticide such as clothianidin (Arena) or dinotefuran (Safari) may be used and should provide season long control (i.e. through the second generation). Growers have noted that dormant oil applications, in addition to the above applications, have helped in managing JMS. For more information on JMS see our UME Fact Sheet at: or an IPM webinar on JMS at: A newly hatched Japanese maple scale crawler is usually purple to light pink in color. 5 When crawlers first settle they begin to make a wax cover that almost looks powdery. The newly settled crawler is underneath. Photo: P. Shrewsbury, UMD)

6 Witchhazel Gall Aphids We continue to receive reports of witchhazel gall activity. Kevin Nickle brought in a birch sample from Timonium with a heavy aphid infestation. There were several clusters of lady bird beetle eggs among the aphids. As soon as the beetles hatch, they will have a food source readily available. Orange lady bird beetle eggs among a large population of aphids Powdery Mildew on Dogwood Paul Wolfe, Integrated Tree Care, reports finding powdery mildew on Cornus florida in the Bethesda area. An infection will often cause the new growth to be twisted or deformed. Older infected leaves often develop purple blotches that progress to dead areas. If necessary, fungicide options include Banner MAXX, Cleary s 3336, Compass, Heritage, Strike, Eagle, and Systhane. Applications should be started when powdery mildew first appears. Repeat applications according to the label. When planting dogwoods, choose resistant cultivars such as Cherokee Brave, Jean s Appalachian snow, Karen s Appalachian Blush and Kay s Appalachian Mist. Powdery mildew on Cornus florida Photo: David Clement, HGIC Powdery Mildew on Euonymus This spring, we continue to get reports of major infections of powdery mildew on euonymus. Powdery mildew on euonymus is a perennial problem and has a never ending infection cycle especially on tightly sheared hedges or plants in the shade. Spraying now will help keep some of the foliage from dropping, but will not cure the problem. The problem will lessen as drier, warmer weather occurs and will return in the fall if rain and cooler weather returns. The best remedy is to open up the plant structure to allow better air movement. Frogeye Leaf Spot on Maple Leaf galls are fairly common on trees such as maples. A gall is actually plant tissue that has developed as the result of feeding or other activity of insects or mites. Plant hormones are involved when the pest interferes with leaf development in the spring. There are also galls caused by fungi, bacteria, and other organisms. The frogeye or eyespot gall shown in the photo is caused by a cecidomyiid fly, Acericecis ocellaris (Osten-Sacken). Once the gall appears on the leaf, there is no way to control it. Preventing most leaf galls is extremely difficult. However, other than being unsightly, most leaf galls are not harming the tree or shrub. Leaf spot on maple Photo: Rich Anacker, A&A Tree Experts 6

7 Caterpillar on Elderberry (Sambucus) We had an unusual occurrence of a caterpillar that was found this spring in the tips of elderberry (Sambucus). It is the stalk borer, Papaipema nebris. It overwinters as an adult, lays an egg in the plant tip, and the larvae are active at this time of year. It is usually found on field crops, but this year it found some elderberry to infest. Stalk borer in elderberry stem Photo: Marie Rojas Slugs Steve Sullivan, The Brickman Group, and Bob Mead, Mead Tree Experts, are both reporting heaving feeding damage from slugs this week on groundcovers and perennials. Please let me know (sgill@umd.edu) if you are seeing an unusually high amount of feeding from slugs this year. Gymnosporangium Rusts Cedar-apple rust, cedarhawthorn rust and cedarquince rust are three related rust diseases and a new Japanese rust is similar. These diseases are very evident on Eastern Red Cedar (Juniperus virginiana) and some prostrate junipers in the spring as red-orange galls on branches or along Cedar apple rust on juniper Cedar quince rust on amelanchier Photo: David Clement, HGIC stems. In moist spring Photo: Steve Sullivan, The weather these galls swell Brickman Group and extrude gelatinous spore tendrils. Quince rust galls produce gelatinous masses of reddish-orange fungal spores on infected twigs. Rust spores within these tendrils are carried by wind where they infect the leaves, fruit, or stems of apple, hawthorn or quince, which are the alternate hosts for these diseases. These infections cause early leaf defoliation, fruit drop, and twig dieback along branches. Highly susceptible, heavily infected deciduous alternate host plants may be defoliated by mid-summer. Leaf spots are conspicuous and detract from ornamental value. The loss of leaf area due to spotting and defoliation reduces the vigor of trees, decreases yields, and makes the plants more susceptible to winter injury and other diseases. Most infected fruit drops in June, while the remainder may be misshapen, cracked, and subject to secondary fruit rots. Quince rust galls on twigs may result in branch dieback and distorted growth. Management: 1.) Separate alternate hosts. Do not plant susceptible apples near susceptible junipers: a distance of 1 to 2 miles greatly reduces infection. (This is obviously not practical in areas where Eastern red cedar is common.). 2.) Hand pick and destroy cedar galls by April 1, before the spore-producing tendrils are formed. Cedar galls are most conspicuous and easy to see in wet weather when the orange spore tendrils are extruded. After the orange tendrils are produced, it is too late to prevent spore dispersal. 3.) The best choice for landscapes is to select resistant cultivars. 4.) Fungicides can be used, however treatments would require extensive spraying until late summer. 7

8 Beneficial of the Week, Paula Shrewsbury We have had some wet weather and I have noticed an increase in slug activity. Slugs are gastropod molluscs. Biologically slugs are somewhat interesting organisms. For example, their use of muscular contractions for locomotion, and the fact that they are hermaphrodites two individuals exchange sperm and both produce eggs. Slugs are not usually thought of fondly by many first because they eat and damage plants, followed by the fact that they produce slimy mucus which is somewhat disgusting. When controlling slugs, the use of baits is the more common tactic. However, it is important to know Convergent lady bird beetle is a species that feeds on slugs Photo: David Cappaert, Michigan State University, Bugwood.org This ground beetle, Sphaeroderus stenostomus, is called a slug eater Photo: Pennsylvania Department of Conservation and Natural Resources - Forestry Archive, Bugwood.org that other organisms eat slugs and provide some level of biological control. For example, some frogs, toads, snakes, hedgehogs, salamanders, turtles, rats, and birds consume slugs. Some slugs are carnivorous and are predators of other slugs and snails. Carnivorous slugs will follow the slime trail of a slug as part of its hunting strategy. Beneficial nematodes, such as Phasmarhabditis hermaphrodita, are commercially available (may not be available yet in the U.S.) and target several common slug species. Juvenile stages of the nematodes actively search for slugs. Nematodes enter the slug through the breathing pore (pneumostome) in the slug s mantle. Nematodes release bacteria into the slug, which stop the slug from feeding and eventually kill it, and the nematodes feed on the bacteria. This is a nice mutualistic relationship that benefits everyone but the slug. There are flies known as marsh flies (family Sciomyzidae) whose larvae are active in soil and are predators or parasites of snails, snail eggs, and slugs. The larvae of some species of ground beetles (family Carabidae) and rove beetles (family Staphylinidae) are carnivorous and actively hunt slugs, worms and other insects. These beetles are frequently found under logs or stones, in soil, and other habitats that also favor slugs. Lady beetles have also been seen feeding on slugs. Encouragement of these predators by providing habitat, combined with other tools such as sanitation, handpicking (yuck), traps, barriers, and baits, will help in the battle against these little slimers. Plant of the Week, Ginny Rosenkranz There is a lot of interest in planting edible landscapes, and many plants are very suitable for providing both food and function in a landscape design. Blueberry bushes are often one of the plants listed and, if the site is well chosen, the plant makes a lovely addition as a shrub to a multi- shrub border, as a foundation plant or as a grouping of plants. The main concern with planting and caring for the Northland lowbush 8 Blueberry flowers (left) and a shrub in a landscape (right) Photos: Ginny Rosenkranz, UME

9 blueberry (Vaccinium corymbosum angustifolium) is to amend the soil so that it is moist but well drained with a soil ph between This is a very low soil ph and many normal foundation or shrub border plants need a much less acidic soil. The plants also prefer full sun and some mulch at the base of the roots to maintain soil moisture. The mulch should be limited to less than 1 inch as it becomes a convenient cover for voles as they travel between the soil and the mulch, hiding from their natural predators of hawks and cats. Northland lowbush blueberry plants are hardy from USDA zone 2-8, but the name emphasizes the need for cooler temperatures for the best growth. The flowers are white with a pinkish tint and are shaped like a small bell or urn. The deciduous leaves are a medium green, lance-shaped and arranged in an alternate fashion on the stem. An added value to the landscape is that the leaves turn a bright red, orange or yellow in the crisp fall air. The berries, which are wonderfully tasteful and full of antioxidants, are round, blue to a blue black and are often eaten by the local birds as soon as they become ripe. The color of the blueberry fruit turns the proper color, but the grower should wait a day or so for the sugars in the fruit to form. There are few insect or disease pests of the blueberry plants if grown in the landscape. Plant Phenology: What s in bloom PLANT PLANT STAGE (Bud with color, First LOCATION bloom, Full bloom, First leaf) Catalpa speciosa Full bloom (May 13) Landover Clintonia umbellulata First bloom (May 14) Silver Run Cotinus obovatus Full bloom (May 14) Silver Run Diphylea cymosa Full bloom (May 14) Silver Run Kalmia latifolia Little Linda and First bloom (May 14) Silver Run Carousel Menziesia pilosa Full bloom (May 14) Silver Run Paeonia veitchii Full bloom (May 14) Silver Run Physocarpus opulifolius Luteus Full bloom (May 14) Silver Run Rhododendron Maximum Roseum First bloom (May 14) Silver Run Scutellaria serrata First bloom (May 14) Silver Run Smilacina racemosa First bloom (May 14) Silver Run Stransvesia davidiana Prostrata and First bloom (May 14) Silver Run Winterthur Stewartia sinensis Full bloom (May 14) Washington D.C. Styrax americanus Kankakee form First bloom (May 14) Silver Run Syneilesis aconitifolia First bloom (May 14) Silver Run Tradescantia virginiana Full bloom (May 16) Ellicott City Zenobia pulverulenta Woodlanders Blue Full bloom (May 14) Silver Run Degree Days (As of May 17)* Baltimore, MD (BWI) 653 Dulles Airport 657 Frostburg, MD 358 Martinsburg, WV 617 National Arboretum 842 Reagan National 842 Salisbury 447 *As of May 11, 2012, degree day calculations are from weather.com growing degree day calculations instead of NOAA min and max temperatures. 9

10 Natural Resources Careers Camp (NRCC) for High School Students They are still looking for students to attend this year s program. This camp is celebrating 40 years of introducing high school students to careers and college studies in forestry, wildlife management, fisheries and arboriculture. The camp is sponsored by the Maryland Association of Forest Conservancy District Boards, The Maryland Forestry Boards Foundation, The Maryland Department of Natural Resources, Forest Service and Allegany College of Maryland. Each year at camp we dedicate an entire day to arboriculture which includes at hot line demo from Pepco, climbing trees with Bartlett Tree Experts and pruning and planting with Davey Tree Experts. Interested students can go to the following website to apply and to learn more about NRCC. Upcoming Programs Invasive Species Identification and Management Seminar May 23, :30-3:15 Location: Government Center Parkway, Fairfax, VA Cost: Free, but registration is required. To register please go to: Contact: Jack Baggett , John.baggett@ fairfaxcounty.gov ASCFG Mid-Atlantic Regional Meeting June 18, 2012 Roost Flowers and Design Location: Virginia Beach, Virginia ascfg.org MNLA Field Day June 21, 2012 Location: D.R. Snell Nursery, Union Bridge, MD Maryland Christmas Tree Association s Summer Meeting June 30, 2012 (Saturday) Location: Taylor Sines Woodlake Tree Farm, Oakland, MD Contact: IPPS Eastern Region Annual Meeting October 10-13, 2012 Location: Brandywine Valley, Pennsylvania 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.