CONTROLLING WIREWORMS WITH NEONICOTINOID INSECTICIDES IN WHEAT
Proposed by: Aaron D Esser
Presenter: Esser, A.D. , Extension Agronomist, Washington State University Extension, Ritzville, WA 99169
Wireworm (Limonius spp.) populations and crop damage have been increasing in both spring and winter wheat (Triticum aestivum L.) production across eastern Washington. After nearly 30 years of use, the pesticide Lindane was withdrawn by the Environmental Protection Agency. Today nearly all spring cereal crop acres throughout eastern Washington are treated for wireworm control with neonicotinoid insecticides such as Cruiser® (thiamethoxam) and Gaucho® (imidacloprid) at rates between 0.190-0.315 oz/cwt. A majority of winter wheat acres are also being treated with these insecticides at similar rates. At these rates, the neonicotinoids are toxic to wireworms but at sub-lethal doses, or in other words they repel or provide some seedling protection only. Two on-farm tests (OFT) were initiated in the spring of 2008 to examine wireworm control with higher than recommended neonicotinoid insecticide applications to find a lethal dose that will reduce wireworm populations and improve yield and economic return over costs. Both OFT’s are a RCBD with 4 replications and 10 and 15 acres in size. At Dewald’s farm Gaucho at 2.0 oz/cwt had a trend for improved yield, economic return over costs, and reduced wireworm populations and additional research is needed. At Sheffels’ farm Cruiser applied at 0.50 and 1.00 oz/cwt has significantly improved yield and economic return over costs compared to applying 0.00 and 0.25 oz/cwt, but has not reduced wireworm populations.