Impacts of bioassay type and source population size on insecticide resistance assessment in the German cockroach (Blattella germanica)

The German cockroach (Blattella germanica) is one of the most critical urban pests globally due to the health risks, such as asthma, it imposes on people. Insecticides are known to manage their large population sizes, but the rapid rate at which cockroaches develop resistance is a continuing problem. This can be expensive and time-consuming for both the consumer and the pest management professional (PMP) applying the treatment. Each cockroach population is unique because different strains have different resistance profiles, so resistance profiles must be considered. This thesis addressed this little-studied issue in a controlled laboratory setting. Cockroach strains from Indianapolis, Indiana, Danville, Illinois, and Baltimore, Maryland, were used. Four insecticide active ingredients most used by consumers and PMPs were selected for testing in vial bioassays to establish resistance profiles. No-choice and choice feeding assays with four currently registered bait products were performed to assess the impacts of competing food and circadian rhythms on bait resistance levels. The results indicate that emamectin benzoate is the most effective active ingredient in causing the highest mortality in all strains in vial bioassays. No-choice assays confirmed vial assay results the best, with Optigard (emamectin benzoate) being the most effective bait in all strains. The results acquired from these studies can help develop rapid tests to use in the field based on the no-choice feeding assay while also adding more information supporting current resistance and cross-resistance evolution theories.