Action of amorphous silica dusts on the German cockroach Blattella germanica (Linneaus) (Orthoptera: Blattidae)

Abstract

AbstractAdult male German cockroaches were exposed to deposits of amorphous precipitated and pyrogenic silicas in continuous and discontinuous contact bioassays. LC50S of precipitated silicas in the former case generally increased with oil adsorption capacity of the dusts; variability in response in discontinuous contact bioassays was apparently due to grooming of appendages following pick-up of dust aggregates. The toxicity of silica deposits in half-treated choice boxes varied with relative humidity and was effectively eliminated at 95% r.h. or when free water was provided. Cockroaches accumulated in the untreated side of the box irrespective of r.h.; the mechanism of this effect is discussed.