Imidacloprid and thiamethoxam are the most commonly-used insecticides for control of Colorado potato beetle. They are usually applied at planting in furrow or as seed treatments to protect the crop against overwintered adults and first generation larvae. Our objective was to determine effects of (1) sandy loam vs. organic soil, (2) in furrow application vs. seed treatment, (3) application rate, and (4) imidacloprid susceptible vs. resistant beetles on length of adult control. Potatoes were grown in the field in sandy loam or organic soil (70% organic matter) in 2002 and 2003 using standard commercial practices. Foliage was collected from plants and returned to the laboratory for no-choice feeding assays with field collected or laboratory reared Colorado potato beetle adults. Soil organic content, application rate, and insecticide resistance status significantly affected length of control. There appeared to be an interaction between soil type and application method, with seed treatment often giving longer effective control than in furrow application in organic soil but not in sandy loam soil. More research is needed to explore deeper and understand these interactions and whether environmental factors such as excessive rainfall or irrigation may also impair insecticide control.
Species 1: Coleoptera Chrysomelidae Leptinotarsa decemlineata (Colorado potato beetle)
Keywords: imidacloprid, thiamethoxam
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