Differential toxicological responses of brownbanded and German cockroaches (Blattodea: Ectobiidae) to commercial gel baits.

The brownbanded cockroach, Supella longipalpa (F.), is a cosmopolitan pest cockroach that infests indoor environments. Compared to the more prevalent German cockroach, Blattella germanica (L.), S. longipalpa has higher temperature requirements but can infest a wider range of environments within structures under suitable conditions. Little is known about the toxicity of gel baits against S. longipalpa relative to that of B. germanica. This study evaluated toxicological responses of brownbanded and the German cockroach to commercial gel baits (Advion Evolution, Maxforce FC Magnum, Maxforce Impact, Alpine, Vendetta Plus, and 1% isocycloseram) using open test arenas and Ebeling choice boxes. Results showed that gel baits were less effective against S. longipalpa. Supella longipalpa survived 3.3 to 10.2× longer than B. germanica when exposed to most bait formulations in open arenas. Gel baits showed lower performance index values against S. longipalpa than against B. germanica in choice boxes. Based on the low performance index values, it is predicted that Maxforce FC Magnum and Vendetta Plus would be ineffective in treating S. longipalpa infestations in the field. Differences in gel bait performance between the 2 species are likely due to the lower palatability of gel baits to S. longipalpa, arising from differing nutritional and moisture requirements. Correlation and regression analysis showed a direct relationship between the data obtained from both assays for S. longipalpa. While open arena bioassays are useful in comparing the toxicity of different gel baits, choice boxes replicate field conditions more closely and allow a more accurate evaluation of bait performance.