TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers Commercial Horticulture August 15, 2014 In This Issue... - Weather and powdery mildew - Invasive worm species - Cypress twig gall - MDA pesticde container recycling - Fall webworm - A new herbicide - Biocontrol of varroa mite - Ambrosia beetles - Orangestriped oakworm - Lace bugs - Two galls on witchhazel Weed of the Week Plant of the Week Phenology Degree Days Announcements 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 Nancy Harding, Faculty Research Assistant 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) Sunny Days and Cool Nights = Powdery Mildew Weather The summer temperatures have been great this July and August with many night temperatures getting fairly cool. This sort of weather is perfect for powdery mildew to show up on dogwoods, euonymus, susceptible crape myrtle species, rudbeckia, your customer s squash, pumpkins, and basil. IPMnet Integrated Pest Management for Commercial Horticulture extension.umd.edu/ipm 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 This robber fly was perched on the Kousa dogwood and on the lookout for prey to catch here at the research center Stormwater Management Program August 20 and 21, 2014
Invasive Worm Species By: Stanton Gill Last week I received an email inquiring about invasive earthworms. We have to deal with invasive weeds, diseases, mites, and insects. To add to this list we have an invasive worm damaging native plantings that is increasing its range. This worm, Amythas agrestic, has many common names including Asian jumping earthworm, Georgia jumpers, Alabama jumpers or crazy snakeworms. I am not sure why people are trying to pin a state name on an invasive species. This worm is very popular with fisherman since it wiggles around on the hook attracting fish. In the south it is very popular for attracting catfish. Unfortunately, fisherman purchase the worms and then discard them near streams and in wooded areas. The worm is changing the habitat of the forest. The problem is this earthworm is much more destructive and aggressive than European species. This earthworm alters the soil structure and chemistry significantly. It is clear that introduced earthworms can significantly alter soil structural properties, organic matter and nutrient dynamics, and plant and animal communities above and belowground. In wooded areas it breaks down leaves and organic material so rapidly it reduces the growth of native understory plants. Often invasive species of plants move into this environment. Amythas species are turning up in gardens in New England and even damaging golf course greens in Kentucky. Dan Potter, University of Kentucky, is working on controlling Amythas species in golf greens where they create large piles on putting greens. Dan Gilrein, Cornell University, reported seeing wood mulch nature trails in Delaware where Amythas species churned the woodland mulch so the mulch paths were totally destroyed. There is not a whole lot that can be done once the aggressive worms are introduced into a woodland, but it is being recommended to fisherman that they dispose of Amythus worms when they are finished fishing and not release them into woodland soils. Cypress Twig Gall Midge Andy Ross, RTEC Tree Care, sent in a photo of galls on baldcypress that are caused by the cypress twig gall midge. Orange-yellow midge fly larvae (maggots) develop and overwinter within the galls. There are two generations per year. Control: Pruning can be done to reduce the number of galls present. Remove and destory dropped galls in fall or spring to reduce the numbers of the next generation of adults that will emerge next spring. There are several species of wasps that parasitize gall-forming insects and help reduce the number of galls formed. Pesticides are usually not recommended. Timing of chemical controls is critical because Even though it is called a twig gall, the galls actually arise from the base of leaflets applications need to be made before galls begin Photo: Andy Ross, RTEC Tree Care to form. Maryland Department of Agriculture Pesticide Container Recycling MDA 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
Fall Webworm By: Stanton Gill Fall webworm populations are high in 2014 and your customers may see the ends of branches with silky webbing in August. This is easy to deal with just prune out the webbing. The webbing produced by fall webworms is evident on many trees this summer New Herbicide By: Stanton Gill, UMD, and Jeff Derr, Virginia Tech Marengo is a long residual preemergence herbicide that effectively controls annual grasses such as crabgrass and annual bluegrass as well as many annual broadleaf weeds such as spurge. Marengo will not control perennial weeds such as yellow nutsedge. The best fit for the liquid form is as a directed spray around established trees in field nurseries. The best fit for the granular form of Marengo is in container production. The Marengo label mentions treatments to greenhouse floors, but we have not tested it for this use. For greenhouse use, treatments should be made prior to moving plants into the house. Irrigate to activate the herbicide and allow the treatment to dry prior to moving plants into the greenhouse. Only greenhouse floors can be treated with Marengo. Marengo does have some postemergence effects, especially on herbaceous plants. Since the postemergence control from Marengo is limited, a postemergence herbicide should be added when making applications in field nurseries. Marengo is a root inhibitor so ornamental plants to be treated must have an established root system. The active ingredient in Marengo, indaziflam, is sold under the trade name Specticle for use in bermudagrass turf and in landscape ornamentals. Indaziflam is active at very low use rates, 0.0224 to 0.075 lbs active ingredient per acre. Rates for the sprayable form of Marengo is 7.5 to 15.5 fluid ounces per acre with a maximum rate per 12 months of 18.5 fl oz/a. For Marengo G, the application rate is 100 to 200 pounds per acre, with a maximum of 400 pounds per 12 month period. For instance, one could make 2 applications per year of Marengo G at 200 lb/a or 2 applications of sprayable Marengo at 9 fl oz/a. Indaziflam has a different mode of action (cell wall synthesis inhibitor) than other premeergence herbicides so it fits well into herbicide rotation programs to minimize the development of herbicide resistance. Biological Control of Varroa Mite in Honey Bee Colonies By: Stanton Gill Varroa mite is a major pest in honey bee colonies. A predatory mite that has been used for fungus gnat control is now being use in honey bee colonies. Hypoapis miles was tested by researchers and honey bee keepers in Canada during 2013 for the effects of the predatory mite on the numbers of varroa mites in infected hives. Positive results were recorded. Ambrosia Beetles We heard from someone in Bucks County in Pennsylvania that the second generation of ambrosia beetles were active on yellowwood. Areas of the bark were wet and frass tubes were evident. If you see these signs on trees, then it is time to apply a control measure. 3
Orangestriped Oakworm Richard Chaffin, The Brickman Group, is finding orangestriped oakworms active in Baltimore County on August 14. Caterpillars will continue to be active through September and are often found on sidewalks and roads when in search of a place to pupate. There is an ichneumonid wasp that parasitizes this caterpillar. Later instar orangestriped oakworms can cause defoliation on trees. Since the defoliation occurs late in the season, many trees are able to recover from the damage. Photos: Rchard Chaffin, The Brickamn Group Lace Bugs John Speaker, IPM Scout, is finding lace bugs in high numbers on hawthorn, serviceberry, London plane tree and silver linden in Gaithersburg. Two Galls on Witchhazel Two galls caused by two different species of aphids can be found on witchhazel. Marty Adams, Bartlett Tree Experts, found witchhazels with both galls present. One is the spiny witchhazel gall caused by the spiny witchhazel gall aphid, Hamamelistes spinosus, which makes spiny galls on the buds. The other gall is caused by the witchhazel leaf gall aphid, Hormaphis hamamelidis. This aphid causes conical galls on leaves. The alternate host for both aphids is birch. Witchhazel leaf gall (left) and spiny witchhazel gall (right) are two galls caused by aphid species that have birch as their alternate hosts 4
Weed of the Week By: Chuck Schuster, UME Mulberry tree, Morus spp, is a tree found growing in some landscapes, fence rows, and unmanaged areas. This tree can grow to heights of 50 feet, growing very quickly as a young tree and slowing down as it matures. The fruit is edible and desired by many, including wildlife that helps spread the seeds. The leaves are alternate, often lobed (Photo 1) on young shoots more often than on the mature trees themselves. Leaf margins are serrated. The fruit starts out as white to yellow, and as it matures turns black to red in color. The mulberry tree is a stump sprouting tree, meaning that if it is cut off it will sprout from the stump not from the roots. Apply triclopyr (Garlon or Pathfinder II) to the cut stump soon after cutting. Pathfinder II can be used as a basal treatment, as the tree has a thin bark. A foliar application of triclopyr and 2, 4D will work well on small trees. Use caution to not contact desired species in doing so, remembering that drift and volatilization can damage desired species of plant material. Photo 1 above shows the lobed mulberry leaves and Photo 2 on the right shows the alternate pattern of the leaves Photos: Chuck Schuster, UMD Plant of the Week By: Ginny Rosenkranz, UME Pinus strobus Pendula, weeping white pine, is art for the outdoors. The tree is covered with beautiful soft, flexible, 2-4 inch blue-green needles that have a row of white stomata on the inner surface and are arranged in bundles of five that persist on the tree for two years. Older needles fall from the tree in late summer to early fall, often causing homeowners to think their trees are dying. Unlike most white pine, Pendula or weeping white pine grows only 6-15 feet tall with a spread of 20-30 feet, depending on pruning and training. The branches grow horizontally for a short while and then cascade down to sweep to the ground, giving the tree a wonderful structural look. The branches that do land on the ground can often act as a ground cover. Because of their artistic look, they are best used in the landscape as a specimen, as living art or as the focal point of a small courtyard. 5
They are cold tolerant in USDA zones 3-8 and prefer to grow in full sun and moist, well drained gravel or sandy soils with a ph under 7. Weeping white pines are not tolerant of salt and are very sensitive to air pollution, especially ozone and sulfur dioxide. They are hardier and happier in the colder rather than the warmer southern counties of Maryland. White pine blister rust of the bark is usually fatal and the alternate hosts which are currants and gooseberries should never be planted nearby. White pine weevil, bark beetles, white pine shoot borer, pine sawfly, scale and aphids can be insect pests. A weeping white pine stands out nicely in this landscape with the bridge as a backdrop Photo: Ginny Rosenkranz, UMD PLANT PLANT STAGE (Bud with color, LOCATION First bloom, Full bloom, First leaf) Helianthus microcephalus First bloom August 11 (Columbia Sedum Autumn Joy First bloom August 14 (Ellicott City) Degree Days (As of August 14) 2014 2013 2012 2014 2013 2012 Baltimore, MD (BWI) 2460 2609 3090 Dulles Airport 2340 2635 2992 Frostburg, MD 1538 1653 1965 Martinsburg, WV 2365 2438 2803 National Arboretum 3031 2988 3497 Reagan National 3031 2988 3497 Salisbury 2709 2899 3196 St. Mary s City 2546 2764 3257 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. 6
Upcoming Conferences Stormwater Management Program*** August 20 and 21, 2014 TWO Locations: August 20 - Montgomery County Extension Office, Derwood, MD August 21 - Robinson Nature Center, Columbia, MD 2014 FALCAN Truck and Trailer Safety Seminar August 27, 2014 Location: Urbana Volunteer Fire Department, 3602 Urbana Pike, Urbana MD 21704 Program takes place both indoors and outdoors. Visit www.falcanmd.com to download a registration form. Email contacts; dfelice@synateksolutions.com or grove@ alpineservices.com Reducing Lawn Fertilizer Use and Stormwater Runoff September 17, 2014 Location: University of Maryland Paint Branch Turfgrass Research and Education Facility, College Park, MD A brochure is available online 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 David Clement Plant Pathologist hgic.umd.edu Andrew Ristvey Extension Specialist aristvey@umd.edu Ginny Rosenkranz Extension Educator rosnkrnz@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.