Graduate Thesis Or Dissertation

Monitoring and Evaluating the Susceptibility of Colorado Potato Beetle, Leptinotarsa decemlineata Say, against Insecticides in the Columbia Basin of Northeastern Oregon

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  • Potato (Solanum tuberosum L.) is among one of the largest and most important staple food crops in the world. One of the most productive growing potato regions is the USA is the Oregon and Washington Columbia Basin. Both states produce approximately 26% of the USA potatoes in the market. In recent years, producers are facing difficulty in controlling “old” and “emerging” potato pests because changes in regulations, “softer” chemistry, global climate variation, new emerging pests compromising pest management program, etc. The Colorado potato beetle, Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae), is one of the most important defoliating insect pests affecting potatoes. This insect is notorious for its destructive feeding behavior, but most importantly, its rapid ability to develop resistance to insecticides. This work centers on developing baseline information regarding the susceptibility of L. decemlineata against common insecticides. The title of this thesis is “Monitoring and evaluating the susceptibility of Colorado potato beetle, Leptinotarsa decemlineata Say, against insecticides in the Columbia Basin of northeastern Oregon” and it is divided into three chapters. The first chapter is a summary of the current body of knowledge related to L. decemlineata in the USA, including description of L. decemlineata biology, ecology, and management of one of the most important economic potato pests. The second chapter describes a laboratory-based bioassay conducted at the OSU Hermiston Agriculture Research and Extension Center to develop LD50s (lethal doses to kill 50% of the population). In this study, L. decemlineata adults and larvae from three different populations from the Columbia Basin, and one population from Wisconsin, were used to evaluate susceptibilities against insecticides; treatments included: abamectin, imidacloprid, and spinetoram. Data gathered from this study suggested that all three insecticides are still effective in controlling L. decemlineata in the Columbia Basin however, we recommend that pest resistance management programs must be implemented. The third chapter presents results from a 2-year field study to determine if neonicotinoids such as imidacloprid and thiamethoxam applied in-furrow or seed-treated ‘at planting’ are still effective in controlling L. decemlineata; additionally, investigating if both compounds have an impact on natural enemies. Our results indicated that thiamethoxam and imidacloprid formulations do not affect natural enemies and are still effective controlling L. decemlineata protecting the crop in average up to 8 weeks after treatment. These studies provide much needed baseline information related to this pest that will allow producers and integrated pest management practitioners to develop strong long-term management programs.
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  • Pending Publication
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  • 2020-01-03 to 2022-03-09



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