Toxicity and in vitro metabolism of t-permethrin in eastern subterranean termite (Isoptera : Rhinotermitidae)

Toxicity and metabolism of t-permethrin were evaluated in two colonies (UF and ARS) of tie eastern subterranean termite, Reticulitermes flaavipes (Kol lar), collected in Gainesville, FL. The UF colony (LC50 = 1.86 mu g per via l) was approximately twofold more tolerant of t-permethrin than the ARS col ony (LC50 = 0.89 mu g per vial) at the LC50. The synergists piperonyl butox ide and S,S,S-tributylphosphorotithioate increased t-permethrin toxicity fo ur- and threefold (at the LC50) in the UF and ARS colonies, respectively. D espite these differences in t-permethrin susceptibility, microsomal oxidase activities toward surrogate substrates (aldrin epoxidase, and metlloxyreso rufin O-demethylase), cytochrome P450 content, and microsomal esterase acti vity toward alpha-naphthyl acetate did not differ significantly between the colonies. Moreover, no significant differences in qualitative and quantita tive metabolism of [C-14] t-permethrin were observed between the UF and ARS colonies for three enzyme sources (microsomal oxidase, microsomal esterase , and cytosolic esterase). Based on in vitro metabolism assays, the major d etoxification route of t-permethrin in the UF and ARS termite colonies appe ars to be hydrolysis catalyzed by microsomal esterases.