RESUMO
BACKGROUND: Resistance monitoring is an important aspect of insect resistance management and the preservation of insecticide efficacy. The adult vial test (AVT) is most often used for resistance monitoring for a variety of insects. A potential alternative method is feeding disruption where resistant insects are distinguished from susceptible insects on the basis of their ability to feed on insecticide in nectar containing a colorimetric marker to measure feeding. The advantages of a feeding disruption test (FDT) for lepidopteran adults might include a more rapid assay than AVT, an assay format easier to prepare, a bioassay applicable to both oral and contact insecticides and the provision of food and water during the course of the test. The objective of the present work was to determine the feasibility of an adult FDT. RESULTS: Heliothis virescens moths fed permethrin and spinosad in dyed nectar yielded dose-dependent ingestion, fecal production and mortality data. A permethrin diagnostic dose distinguished pyrethroid-resistant from pyrethroid-susceptible moths, based on fecal production. CONCLUSION: Proof of concept was demonstrated for an adult FDT in which resistant moths were distinguished from susceptible moths on the basis of the ability of the insect to feed on insecticide in dyed nectar and produce dyed feces.
