Feasibility of a novel feeding disruption test (FDT) bioassay kit for rapid resistance detection of sucking pests of cotton

Recent reports of tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), resistance to several classes of cotton insecticides, and of variable insecticide susceptibilities of stink bug species that damage cotton, highlight the need for assays to monitor for the development of insecticide resistance. Topical-application and vial assays in current use have several limitations, including that these assays rely on a mortality endpoint which is often not easy to read (requires probing the insect and/or discriminating between knockdown versus death) and un-necessarily extends the time to the assay endpoint. Feeding disruption test (FDT) bioassays circumvent these limitations. In FDT assays, insects feed on insecticide in rehydrateable artificial diet mealpads containing a blue indicator dye to mark feeding on the artificial diet. The assay endpoint is the dose-dependent amount of blue feces produced, usually within 24 hours. The objective of the work presented was to determine the feasibility of developing FDT assays for plant bugs and stink bugs. Lab-strain adult tarnished plant bugs, fed different concentrations of â-cyfluthrin and thiamethoxam in rehydrateable NI diet mealpads containing food-grade blue dye in FDT plates, showed a dose-response in production of dyed feces for both insecticides. Lab-strain adult brown stink bugs, Euschistus servus (Say), fed different concentrations of thiamethoxam in nectar also showed a mortality dose response. Brown stink bugs fed NI diet containing food-grade blue dye produced dyed feces. These results demonstrate that dyed diet diagnostic-dose FDT assays can be developed for stink bug resistance monitoring as well as for plant bug resistance monitoring.