Evaluation of the efficacy of 2.15% imidacloprid (ROCO GEL) gel against Periplaneta americana under laboratory and field conditions in Benin

In Benin, cockroaches are infesting urban environments and developing resistance to commonly used insecticides. Therefore, developing alternative insecticides is important for resistance management. The present study aims to test the efficacy of a gel bait formulation-2.15% imidacloprid against the common cockroach Periplaneta americana under laboratory and field conditions in the commune of Abomey-Calavi. Dead and alive cockroaches were compared before and after exposure to 2.15% imidacloprid. In laboratory as well as in the community, the mortality rates of Periplaneta americana were more than 50% in 24 hours after consumption of 2.15% imidacloprid bait. Under laboratory conditions, the mortality rate was 100% after eleven (11) days while in the community, an overall mortality of 86.97% [84.3-89.3] was observed in the restrooms and 84% [76.3-89.9] in the kitchens 8 weeks after treatment with 2.15% imidacloprid. The mortality rate was similar in latrines and kitchens. Overall, mortality among adult cockroaches was 94.85% [92.8-96.5]) versus 65% [58.6-71.0] for nymphal cockroaches. The 2.15% imidacloprid did not prevent egg hatch from ootheca. These results showed that the use of 2.15% imidacloprid can be used to mitigate cockroach resistance to pyrethroid, carbamate and organophosphate insecticides in Benin.