Secondary transmission of toxic baits in German cockroach (Dictyoptera : Blattellidae)

The death rates of three toxic gel baits (fipronil bait, 0.05%; hydramethyl non, bait 2.15%; and abamectin B1 bait. 0.05%) were estimated in Blattella germanica (L.). After ingestion, all three baits killed similar proportions of cockroaches, but they died more rapidly after ingestion of fipronil bai t than after ingestion of abamectin B1 bait or of hydramethylnon bait. Labo ratory experiments evaluated the impact of secondary transmission of fipron il bait and hydriamethylnon bait. Mortality rates caused by secondary trans mission were higher for fipronil bait than for hydramethylnon bait. Under c ontrolled laboratory conditions, secondary transmission occurred mainly thr ough direct contact with, or ingestion of, traces of baits dispersed in the environment by contaminated cockroaches. These traces were either deposite d by "trampling" in the environment or on dead contaminated cockroaches. So cial interactions and cannibalism played a minor role in secondary transmis sion of these two baits.