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Biology and Management of Insects Attacking Turf and Woody Landscape Plants
D.A. Potter
Department of Entomology
Non-Technical Summary
Rapid urbanization in the USA during the past 50 years has increased the need for safe, effective management tactics for insect pests of landscapes and turf. Concerns about environmental impact and hazard of chemical pesticides, and loss of insecticide registrations have fueled this demand.
Pests such as root-feeding white grubs, Japanese beetles, scale insects, wood borers, and leaf-feeding caterpillars cause extensive damage to lawns, landscapes, nursery crops, street trees, parks, and golf courses, amounting to hundreds of millions of dollars in economic loss.
This project will develop new methods for dealing with insect pests of urban landscapes, and contribute better understanding of pest biology upon which future control strategies can be built. The project focuses on biological and cultural control, host plant resistance, and other sustainable tactics.
2009 Project Description
Turfgrass species and mowing height were shown to influence white grub species distributions, incidence of natural enemies of grubs including parasitic wasps and entomopathogens, and digging injury to turf from predatory vertebrates (e.g., skunks). New strains of entomopathogenic nematodes isolated from masked chafer grubs are being evaluated as biological insecticides. Gregarine (Stictospora) parasites were shown to delay pupation and reduce survival of overwintered Japanese beetle grubs.
Field surveys identified parasitic insects suppressing black cutworms in turfgrass and studies were initiated to determine their compatibility with turfgrass insecticides having differing modes of action, as well as compatibility with insect-resistant grasses.
Comparative ecotoxicology of cloranthraniliprole, representing a new class of turf and landscape insecticides (anthranilic diamides), versus prevailing insecticide chemistry (nicotinoids and pyrethroids) was evaluated. Clorantraniliprole had lesser adverse effects on predatory insects, earthworms, and soil decomposers; impact on native pollinators (bumblebees) will be evaluated in spring 2010.
A botanical vermicide based on a by-product of tea oil manufacture was shown to be highly effective for reducing excessive earthworm casts, which are a major problem on closely mowed playing surfaces; efforts to register the product as a bio-pesticide were initiated.
Tall fescue species and cultivars representing a range of structural characteristics were evaluated for suitability for true armyworm (TAW) to test whether selection for improved forage quality may render pastures more vulnerable to outbreaks. TAW exploited softer more digestible cultivars by edge-feeding but overcame the silicaceous edge barbs and trichomes of coarse-textured fescue by switching to window-feeding (scraping mesophyll from surfaces of leaf blades). Soft-textured fescues are probably no more susceptible than standard ones as far as TAW outbreaks, but neither fescue type is resistant.
Honeydew-gathering ants and predators (e.g., lacewing larvae) associated with calico, magnolia, and oak lecanium scales were identified. Excluding ants, which drive away the scales' natural enemies, from infested trees with sticky truck bands resulted in 55% and 68% decline in calico scale densities after one and two years, and > 75% reduction in magnolia scale in one summer. An interesting case of ants using chewed mulch to cover their soft scale "livestock" and protect them from being eaten by syrphid larvae and other enemies was documented.
Replicated field plots with numerous species and cultivars of native and exotic oaks, magnolias, and elms were evaluated for resistance to key insect pests, including soft scales, Japanese beetle, leaf-miners, and gall-makers. In each case, trees showing marked resistance were found, providing a data base for selecting well-adapted cultivars to replace ash, oak, and other street and landscape trees being decimated by invasive pests such as emerald ash borer.
2009 Impact
Pathogens isolated from our grub collections are being identified and evaluated as potential new biological insecticides. Our data on how turf species and site characteristics affect white grubs and natural enemies suggest ways to increase stability and buffer lawns and other turf sites from pest outbreaks. Our research with AgipMNPV, the first large-scale evaluation of a baculovirus for suppressing a turf pest, provides groundwork for developing organic pest control approaches for lawns, golf courses, and sport fields. Our work on improved forage grasses and armyworms suggests that benefits of establishing such cultivars in Kentucky pastures will not be dampened by greater injury from insects.
Establishing economic thresholds for Japanese beetle injury to grapes is helping Kentucky's nascent viticulture industry to reduce insecticide inputs and costs. Our study showing that applying a simple trunk band to exclude ants facilitates natural predation on soft scales and reduces infestations suggests a novel, safe, and inexpensive pest management approach for landscape managers and homeowners.
Our elm evaluations are helping nursery growers, landscapers, and homeowners to choose Dutch elm disease-resistant elms that also are resistant to insect pests, and revealed that a new invasive pest has become established in Kentucky.
2009 Publications
Hammons, D.L., S.K. Kurtural, M. C. Newman, and D.A. Potter. 2009. Invasive Japanese beetles facilitate aggregation and injury by a native scarab pest of ripening fruits. Proc. Nat. Acad. Sci. 106: 3686-3691.
Potter, D.A., C.T. Redmond, K.M. Meepagala, D.W. Williams. 2009. Managing earthworm casts (Oligochaeta: Lumbricidae) in turfgrass using a natural byproduct of tea oil (Camellia sp.) manufacture. Published on-line Dec. 18, 2009; DOI: 10.1002/ps.1896
Wood, T.N., M. Richardson,D.A. Potter, D.T. Johnson, R.N. Wiedenmann, and D.C. Steinkraus. 2009. Ovipositional preferences of the Japanese beetle (Coleoptera: Scarabaeidae) among warm- and cool-season turfgrass species. J. Econ. Entomol. 102: 2192-2197.
Saeki, Y., P. Crowley, C. Fox, and D.A. Potter. 2009. A sex-specific size-number trade-off in clonal broods. Oikos 118:1552-1560.
Redmond, C.T. and D.A. Potter. 2009. The search for biological control of white grubs. U.S. Golf Assoc. Green Section Record. Sept./Oct. 8-12.
Hammons, D.L., S.K. Kurtural, and D.A. Potter. 2009. Impact of Japanese beetle defoliation on first season crop yield and berry quality. Pages 15-16 in 2008 Fruit and Vegetable Crops Research Report, University of KY Agric. Expt. Sta. PR-572.
Hammons, D.L., S.K. Kurtural, and D.A. Potter. 2009. Phenological resistance of grapes to green June beetle damage. Pages 16-17 in 2008 Fruit and Vegetable Crops Research Report, University of KY Agric. Expt. Sta. PR-572.
Brady, C, Condra, J., Potter, D.A. 2009. Resistance of landscape-suitable elm (Ulmus spp.) cultivars to Japanese beetle, leaf miners, and gall makers. Pages 15-16 in 2008 Nursery and Landscape Program Research Report, University of KY Agric. Expt. Sta. PR-571
Vanek, S. and Potter, D.A. 2009. Sustainable management of soft scale outbreaks using ant exclusion. Pages 16-17 in 2008 Nursery and Landscape Program Research Report, University of KY Agric. Expt. Sta. PR-571
Hammons, D.L., S.K. Kurtural, M. C. Newman, and D.A. Potter. 2009. Invasive Japanese beetles facilitate aggregation and injury by a native scarab pest of ripening fruits. Proc. Nat. Acad. Sci. 106: 3686-3691