DEF sensitive esterases in homogenates of larval and adult Helicoverpa zea, Spodoptera frugiperda, and Agrotis ipsilon (Lepidoptera: Noctuidae).

Homogenates of Helicoverpa zea (Boddie), Agrotis ipsilon (Hufnagle), and Spodoptera frugiperda (J. E. Smith) third instars and adults contained S,S,S-tri-n-butyl phosphorotrithioate (DEF)-sensitive enzymes that hydrolyzed trans-cypermethrin and two known esterase substrates, alpha-naphthyl acetate and beta-naphthyl acetate. Except for H. zea with alpha-naphthyl acetate, larval preparations were more active than those of adults, and no marked sex differences were apparent. The hydrolysis of trans-cypermethrin in noctuid preparations were inhibited by DEF, with pI50 values ranging from 4.5 to 6.7. DEF was a potent inhibitor of the degradation of general carboxylesterase substrates alpha-naphthyl acetate and beta-naphthyl acetate in some cases. Electrophoretic studies confirmed the presence in noctuid gut homogenates of one or more DEF-sensitive esterases that hydrolyzed alpha-naphthyl acetate and beta-naphthyl acetate and that were completely inhibited by dichtorvos.