Indoor toxicity and field efficacy of four insecticides against the larva of Rhabdophaga salics Schrank

Indoor toxicity and field efficacy were tested with dipping and spraying methods to determine the efficacies of four kinds of insecticides in controlling the larva of Rhabdophaga salics Schrank.The results indi-cated that 20% Acetamiprid SP had the most significant toxic effect on the larva.Its toxicity index was 1 995.43 and 19.95 times of that of 48% Chlorpyrifos EC,which was used as a regular pharmacy in the local.20% Acetamiprid SP,70% Imidacloprid WDG and 48% Chlorpyrifos EC exhibited better control in the field.Three days after spraying,the corrected efficacies were 60.27%,54.80% and 40.83%,respectively.Seven days after spraying,the corrected efficacies were 79.50%,70.71% and 58.07%.Thirty days after spraying,the seedling pro-tecting effects were 59.74%,50.65% and 46.75% respectively.In actual use,20% Acetamiprid SP,70% Imidaclo-prid WDG and 48% Chlorpyrifos EC should be selected to spray at 300 g·hm-2,150 g·hm-2 and 1500 mL·hm-2,respectively.The three insecticides must be used alternately to postpone the appearance of insecticide resistance of R.salics.