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Biological Control of Arthropod Pests and Weeds
Department of Entomology
The growing emphasis on environmental and food safety issues has intensified interest in the development of biological controls as a means for controlling pests. The effective use of natural enemies in biological control programs is contingent upon understanding their ecology and that of their targets, their interaction with production practices, and the most effective means of using them. The purpose of this project is to improve the use of biological control in controlling pests and weeds.
2009 Project Description
Densities of lady beetles in sweet corn were sampled in 2009 to determine whether the exotic species Harmonia axyridis had become relatively more abundant in this crop since its arrival in Kentucky during the 1990's. Results indicate that it has not, with the native lady beetle Coleomegilla maculata still constituting the majority of lady beetle larvae and adults found in Kentucky sweet corn.
Abundance of predators and parasitoids associated with the milkweed aphid Aphis nerii were sampled in field plots of four milkweed species (common, honeyvine, swamp, and butterfly milkweeds). Abundance of predators was generally similar in 2009 to the pattern seen the previous year. Activity of parasitoids attacking A. nerii was significantly different among host plant species, as was proportion of successful emergence of parasitoids from A. nerii mummies. Lysiphlebus testaceipes was the predominant parasitoid attacking A. nerii, and this parasitoid species attacks many aphid pest species on a variety of crops.
Coleomegilla maculata is an important predator of many non-aphid corn pests, including the corn earworm and the European corn borer. The exotic lady beetle Harmonia axyridis is more specialized in its feeding, primarily attacking aphids and their relatives.
Historically, exotic species have sometimes displaced native species. We were concerned that the exotic H. axyridis might have adversely affected populations of C. maculata in sweet corn, but that does not appear to be the case in Kentucky. Our interest in predators and parasitoids attacking the milkweed aphid reflect our concern that these natural enemies might be adversely affected by feeding on this aphid species.
Milkweeds possess chemical defenses against herbivores and we were concerned that natural enemies might be harmed by feeding on the milkweed specialist A. nerii. Milkweeds, particularly honeyvine and common milkweed, are common within and alongside corn and soybean fields in the Midwestern United States. Thus, it is likely that natural enemies could easily move between milkweeds and crop plants. These studies are ongoing and it is too early to draw definitive conclusions.
Yeargan, K.V., and S.M. Colvin. 2009. Butterfly feeding preferences for four zinnia cultivars. Journal of Environmental Horticulture 27: 37-41.
Decker, K.B., and Yeargan, K.V. 2008. Seasonal phenology and natural enemies of the squash bug (Hemiptera: Coreidae) in Kentucky. Environ. Entomol. 37: 670-678.