Effects of fipronil on detoxifying enzyme activities in Plutella xylostella

The short-term physiological responses of the diamondback moth(DBM) ,Plutella xylostella(L.) to fipronil were studied by measuring detoxifying enzyme activity in 3rd instar larvae.Significantly higher activity of the detoxifying enzymes,mixed-function oxidase(MFO) ,esterase(EST) and glutathione S-transferase(GST) was found in DBM larvae treated with an LC50 value of fipronil compared to the fipronil-free controls.Our results show that fipronil may induce the activities of these three detoxifying enzymes in susceptible strains of DBM and that increased activity of these enzymes reduced the sensitivity of DBMs to fipronil.