Abstract: The contact toxicities of several pyrethroids and conventional organo-phosphates to Dendrolimus punctatus were tested by using microcapillary topical application methods. The results are as follows; pyrethroids showed very high toxicity, such as deltamethrin are 600 times and 1096 times more than dichlorvos and malathion; They are, so far, the most effective and economic insecticides for controlling the pine caterpillares. The pyrethroids are widely used in controlling forest pests in China from the beginning of 1980's. The resistance of Dendrolimus punctatus to pyrethroids has not appeared by 1989. But a tolerant difference was shown. Experimental showed that doses of initial applying compounds could be continually used in the forest area.

Key words: Dendrolirnus punctatus, Insecticide-resistance, Pyrethroid, Toxicity baseline