Observing the Effect of Soil-Applied Insecticides on Wireworm (Coleoptera: Elateridae) Behavior and Mortality Using Radiographic Imaging

Radiographic imaging was used to study corn wireworm, Melanotus communis (Gyllenhal) (Coleoptera: Elateridae), behavior in the soil relative to Irish potato, Solanum tuberosum L. (Solanales: Solanaceae), placed above a barrier of insecticide-treated soil. Behavioral response to three insecticides was evaluated by 1) calculating the percentage of wireworms that breached the zone of insecticide-treated soil, 2) comparing the variability in the mean distance between each wireworm and the center of the tuber in each arena compartment, 3) comparing the cumulative distance of wireworm travel, and 4) comparing incidence and severity of wireworm-inflicted tuber injury. The percentage of wireworms that breached the insecticide zone was significantly lower in the bifenthrin treatment than the untreated check, but not different from clothianidin or fipronil. Limited difference between treatments in relation to the cumulative distance traveled was observed where bifenthrin inhibited travel distance more than other insecticides tested. No difference in variability of movement in relation to the food source was observed between treatments. Bifenthrin and fipronil treatments resulted in the greatest reduction in wireworm injury incidence and severity compared to the untreated check. While bifenthrin suppressed wireworm movement and feeding more than other insecticides tested, exposure to fipronil resulted in higher wireworm mortality at all sample dates.