Comparison of the toxicity of pulegone in larvae of Spodoptera eridania and S. frugiperda : possible involvement of the glutathione S-transferase system

The acute and chronic toxicities of pulegone and menthofuran to larvae of the southern and fall armyworms (Spodoptera eridania and S. Frugiperda) were compared.

The chronic effects of pulegone and menthofuran were more severe in the fall armyworm. Menthofuran was chronically more toxic than pulegone in both species. Acute toxicities exhibit the reverse of these trends. Possible explanations are discussed.

Glutathione S-transferase activity was investigated as a likely factor in differential pulegone detoxification. Endogenous activity was determined in the fatbody, malpighian tubules and testes of both species, and in the gut of both species throughout the last larval instar. Induction of enzymatic activity by dietary chemicals, including several monoterpenes, was studied.

Glutathione S-transferase activity was very similar in the gut and testes in both species, and fairly constant in the gut throughout the last instar. Fatbody and malpighian tubules, however, had higher activity in the southern armyworm. Probably the most significant species difference was the inducibility of activity. Southern armyworm transferase activities were induced to consistently higher levels than were those of the fall armyworm.