Development of strategies for monitoring indoxacarb and gel bait susceptibility in the German cockroach (Blattodea: Blattellidae).

BACKGROUND

Advion(®) cockroach gel bait (6 g kg(-1) indoxacarb) is in widespread use for Blattella germanica (L.) control in the United States. However, baseline susceptibility levels to indoxacarb in German cockroach field populations are not known. Hence, this research sought to develop monitoring strategies to estimate the susceptibility of German cockroach populations to indoxacarb.

RESULTS

Four bioassays were evaluated: topical lethal dose (LD), formulated gel bait lethal time (LT), vial lethal concentration (LC) and gel bait matrix LD. Of these methods, the vial LC and gel bait matrix LD bioassays were the most economical and relevant assessment strategies. For indoxacarb susceptibility monitoring, a two-tiered approach was developed that utilizes diagnostic concentrations and doses in vial LC (30 and 60 µg vial(-1) ) and gel bait matrix LD (1.0, 1.5 and 2.5 µg insect(-1) ) formats.

CONCLUSIONS

A two-tiered susceptibility monitoring strategy was developed that includes testing field populations at diagnostic concentrations and doses in first-tier vial LC bioassays and second-tier gel bait matrix LD bioassays. The vial method facilitates rapid identification of field strains with reduced susceptibility. The feeding bioassay effectively simulates field exposure to Advion(®) and therefore has utility for secondary confirmation of susceptibility shifts and identification of behavioral resistance (i.e. bait aversion).