240 g/L虫螨腈悬浮剂对桑螟防效及对家蚕毒性测定

Effect of 240 g/L Chlorfenapyr Suspension on Controlling Mulberry Phralidid Caterpillar and Its Toxicity Evaluation on Silkworm Bombyx mori

实验室测定,240g/L虫螨腈悬浮剂对3龄起蚕添毒24 h的LC_(50)>3750 mg/L,连续添毒48 h和72 h的LC_(50)分别为1858.2552 mg/L、1207.4615 mg/L,表明240 g/L具有累积效应。田间试验表明,240 g/L虫螨腈悬浮剂750倍(320 mg/L)和1500倍(160 mg/L)对桑螟幼虫的防效显著优于77.5%敌敌畏乳油750倍+40%辛硫磷乳油1500倍。240 g/L虫螨腈悬浮剂320 mg/L和160 mg/L喷于桑树后1 d采叶,对3龄起蚕均无中毒症状和死亡现象,但连续饲养至5龄,茧层率有所下降。240 g/L虫螨腈悬浮剂320 mg/L和160 mg/L喷药的桑叶应间隔7 d后采叶养蚕,以免影响蚕茧质量。

Laboratory tests showed that 24 h continuous feeding of 240 g/L Chlorfenapyr suspension to newly exuviated silkworm larvae at the third instar had the LC50 > 3750 mg/L, 48 h and 72 h continuous feeding had LC50 > 1858.2552 mg/L and 1207.4615 mg/L, respectively, which indicated that the acute toxicity of 240 g/L Chlorfenapyr suspension to silkworm was low, and its efficacy was slow and cumulative. Field experiments showed that effect of 750 times (320 mg/L) and 1500 times (160 mg/L) of 240 g/L Chlorfenapyr suspension on controlling the larvae of phalidid caterpillar was significantly better than that of the combination:750 times of 77.5% dichlorvos emulsifiable oil + 1500 times of 40% phoxim emulsifiable oil. If 320 mg/L and 160 mg/L of 240 g/L Chlorfenapyr suspension agent were sprayed on mulberry trees, and then collected leaves after one day to feed the newly exuviated silkworm larvae at third instar, there was no observable toxic symptom and death. However, decreased cocoon shell rate was observed if continuously feeding to the silkworm larvae until fifth instar. The safe duration of collecting mulberry leaves after sprayed with 320 mg/L and 160 mg/L of 240 g/L Chlorfenapyr suspension agent to feed silkworm is 7 days so as to avoid any negative effect on the cocoon quality.