Correlation of catalase and peroxidase with pesticide tolerance in massonpine caterpillar

Catalase(CAT) and peroxidase(POD) were found to exist in the larvae of Dendrolimus punctatus Walker. The activity of CAT and POD in the fourth and sixth instar larvae were found to be higher than that in fifth instar larvae. After treatment with etofenprox to the larvae, the enzyme activity of D.punctatus showed correlation with tolerance to the pesticide. The activity of CAT and POD increased during exciting stage. Based on the results of toxicity test, it was clear that the pesticide tolerance of massonpine caterpillars increased with larval instars. The lethal dosage of etofenprox to larvae in the fifth and sixth instars increased by 43% and 72% respectively,as compared with that in the fourth instar. It will be rational to carry out chemical control before the larvae being in fourth instar.