Co-variation of insecticide resistance and host-microbe gene expression in geographically distant populations of German cockroaches (Blattodea: Blattellidae).

Insecticides can greatly limit the impacts of cockroaches on indoor environment and human health. Insecticide resistance, however, reduces the efficacy of insecticides and increases insecticide use by both residents and pest control professionals. This study examined the relationship between insecticide cross-resistance and associated gene expression across nine different German cockroach populations from the eastern U.S. Using vial bioassays, we identified significantly correlated resistance between three insecticides from different classes (indoxacarb, lambda-cyhalothrin, fipronil), with potential cross-resistance between indoxacarb and lambda-cyhalothrin being the most strongly correlated. In gene expression studies, we found that cockroach cytochrome P450 expression was most strongly associated with apparent cross-resistance across populations, while microbial gene expression was more variable. These findings provide new insights on cross-resistance and associated mechanisms that can broadly impact resistance management in this important urban pest.