Lepidopteran Adult Feeding Disruption Test (FDT) to Detect Insecticide Resistance

A resistance-monitoring feeding disruption test (FDT) for lepidopteran adults was developed.  Lab-strain H. virescens adults were fed different concentrations of permethrin and spinosad in 10% sucrose containing 0.08 mg/ml trypan blue dye to obtain dose-dependant fecal production and mortality.  A permethrin diagnostic dose of 20 µg/ml distinguished lab-strain pyrethroid-resistant H. virescens from lab-strain susceptible moths on the basis of both mortality and relative amounts of dyed feces.  The assay produced no false-positives or false-negatives (error rate = 0%).