Effects of Isaria fumosorosea infection on different enzyme activities in the larvae of Plutella xylostella

The activities of phenoloxidase (PO) and different antioxidative enzymes, including superoxide dismutase (SOD), perioxidase (POD), catalase (CAT) and glutathione S-transferase (GST) in the 3rd instar larvae of diamondback moth (Plutella xylostella) infected by Isaria fumosorosea were studied. The results showed that activities of PO and antioxidative enzymes in the 3rd instar larvae were significantly affected by I. fumosorosea. PO activity in the infected larvae was always higher than that in the control, and reached a value of 37.4U/g, being 2.6 times the PO activity of the control in 40h after inoculation. The antioxidative enzyme activities were higher than those of the controls at the beginning period of infection, and reached their peaks in 40–48h, then started to decline in 56h,finally became lower than those of the control in 64h, indicating that the physiological activities of P. xylostella larvae were disturbed by the infection of I. fumosorosea.