Studies on the Insecticide-Tolerance of Dendrolimus punctatus to Fenvaleratc

The insecticide-tolerance of Dendrolimus punctatus Walker to fenvalerate was studied in Jiangshu Province through bioassay and the methods of physiology & biochemistry. The results showed that:(1) The insecticide tolerance to fenvalerate increased with the increase of instars and it was 37 times in the 6th instar larvae more than that of the 3rd instar; (2) The resistance to fenvalerate and deltamethrin had not formed yet in Tongshan colony; (3) The activity of carboxyesterase increased gradually with the increase of instars and was greater in Tongshan colony than that in Maoshan colony; (4) The results of dipping and injection showed less difference between the Tongshan and Maoshan colony. The dynamic study on pesticide-penetrating-cuticula of Tongshan colony showed that 43.3% fenvaleratc did not entered cuticula, and that 1.8% fenvalerate remained in integument 8 hours after dipping the larvae.