D3241: Response of a natural enemy of pest flies to a bittering agent used in fly pesticide formulations

House flies, Musca domestica, are a great nuisance to humans and can transmit numerous pathogens to humans and livestock. Manure management, insecticides, and sometimes biological control are used in fly management. The use of insecticides in controlling house flies can also harm non-targeted insects, e.g., pollinators and natural enemies of the flies. In some insecticides used against house flies, apart from the active ingredient, fly pheromone and a phagostimulant, a bittering agent is also included, to prevent accidental ingestion by non-targeted organisms. Denatonium benzoate (DB) is a bittering agent that is used in some fly baits, at a concentration of 100 ppm. The response to DB varies among the few insect species that have been examined. However, there have not been any studies on whether parasitoid wasps, some of which are natural enemies of house flies, show an aversive response to DB. If they do at reasonable concentrations, e.g., at 100 ppm, this would be an additional reason for adding DB to more of the insecticide formulations used against house flies.
In this study, laboratory-reared colonies of parasitoid wasps will be used. Choice experiments will be conducted to assess whether the wasps avoid sugar solutions containing DB. Each wasp will get a choice between a plain 10% sucrose solution and the same solution treated with DB. The concentrations of DB tested will be 0 ppm (control) versus 20 ppm, 100 ppm, and 200 ppm. Consumption will be compared among concentrations.