The influence of competitive food on the performance of several insecticidal gel baits against different life stages of the American cockroach (Blattodea: Blattidae)

The American cockroach, Periplaneta americana (L.) (Blattodea: Blattidae), is a peridomestic pest found worldwide. Insecticidal baits are less widely studied in American cockroaches than in German cockroaches. It is therefore unclear whether commercial baits are effective against American cockroaches. Here we compared the performance of commercial gel bait formulations (Advion Evolution, Alpine, Combat Max, Hot Shot, Invict Gold, Magnetic Roach, Max Force Impact, Max Force FC Magnum, Optigard, Vendetta, and Vendetta Nitro) against five life stages (small, medium, and large nymphs, and adult males and females) of the American cockroach, both with and without competitive food. Survival analysis and median survival time (MST) generally showed that bait efficacy and final 14-day mortalities increased in the absence of competitive food. Combat Max and Max Force FC Magnum (both containing fipronil) were equally effective against all stages, despite the presence of competitive food with MSTs of 48 h (CI = 35.45-70.75 h). Hot Shot (0.05% dinotefuran) and Alpine (0.5% dinotefuran) performed poorly, especially with small and medium nymphs, with final mortalities less than 50% when competitive food was present. MSTs for all other baits were greater with competitive food, 168 h (CI = 122.61-165.38 h), which reduced to 96 h (CI = 89.52-121 h) when not present. Overall, bait efficacy substantially varied among commercial formulations and life stages, with some baits providing consistent control, while others were less effective when competitive food was present. Our study emphasizes that sanitation in and around structures may enhance bait efficacy in controlling American cockroaches.