Response of a chigger, Eutrombicula hirsti (Acari: Trombiculidae) to repellent and toxicant compounds in the laboratory.

Laboratory tests were conducted to compare the response of Eutrombicula hirsti (Sambon) larvae to the compounds dibutylphthalate (DBP), dimethylphthalate (DMP), diethyl methylbenzamide (Deet), benzyl benzoate (BB), and permethrin. The ED50 for E. hirsti of these compounds when applied to filter paper were 0.17 mg/cm2 for DMP, 0.24 mg/cm2 for permethrin, 0.26 mg/cm2 for Deet, 1.42 mg/cm2 for BB, and > 7.21 mg/cm2 for DBP. When impregnated in cloth, DMP, Deet, and BB were highly toxic to larvae at low concentrations, whereas permethrin and DBP were not as rapidly toxic, but were effective.