Comparative toxicities of hydramethylnon, fipronyl and imidicloprid gel baits against field strain of German cockroaches

A study was conducted to determine the comparative toxicity of the three toxicants as baits against the German cockroach.  All the tested German cockroaches were collected from dormitories in Yasuj city, Iran. Adult males and nongravid females as well as small nymph and large nymph were used in the toxicity tests. Ten German cockroach for each developmental stage were placed in separate labeled glass rearing jars of the same size (one liter). There were three replicates (jars) for each stage totalling 120 cockroaches in 12 colony jars for the three gel treatments and equal number of cockroach for each control. Mortality data were analyzed by probit analysis. Results showed 100% mortality for the all baited German cockroaches within 1-5 days. There were significant differences among LT₅₀s (or LT₉₀s) of the three gel bait treatments for the baited German cockroaches. However, there was no significant difference among the LT₅₀ values for the four German cockroach stages when exposed to the three baits. Imidacloprid killed cockroaches more rapidly than fipronil and hydramethylnon respectively.  According to the LT₅₀s, imidacloprid, fipronil and hydramethylnon gel baits were recorded as rapid, quick and slow action baits respectively.