植物性杀虫剂苦皮藤乳油控制菜青虫有效剂量的研究

AN INVESTIGATION OF THE EFFECTIVE DOSAGE OF THE BOTANICAL INSECTICIDE KPT EMULSIFIABLE CONCENTRATE FOR TRE CONTROL OF CABBAGE WORM

测试结果表明 :苦皮藤乳油对菜粉蝶的卵没有直接杀伤作用 ,但卵孵化出的幼虫却有较高的死亡率。对 1～ 5龄不同龄期的菜青虫进行胃毒测试 ,苦皮藤素LC50 分别为 2 4.78mg/kg,72 .5 5mg/kg,1 2 4.35mg/kg,32 1 .2 1mg/kg,1 2 40 .42mg/kg。田间药效试验表明 ,一次施药 5 0mg/kg和 1 0 0mg/kg的苦皮藤乳油对菜青虫的防效差异不显著 ,但保产效果明显不同。研究结果表明 ,苦皮藤乳油防治菜青虫的有效浓度以 5 0mg/kg为宜。

The results of laboratory bioassay showed that KPT EC (the emulsifiable concentrate of Celastrus angulatus Max., an insecticidal plant) had no ovicidal action against the eggs of cabbage worm ( Pieris rapae ),but the mortality rate of the newly hatched larvae of the pest was 81.53% when they were treated with KPT EC at 100 mg/kg. LC 50 of stomach toxicity of KPT EC against 1st, 2nd,3rd,4th and 5th instar larvae of P.rapae was 24.78,72.55, 124.35, 321.21 and 1240.42 mg/kg,respectively. In a subsequent field experiment, a single application of KPT to summer cabbage at the rate of 100 mg/kg at egg hatching peak gave a control efficiency of 60% and increased cabbage production by 36.5%. With a KPT rate of 50 mg/kg in the same periold, the control efficiency was 63.1% and the yield increase margin was 17.3%. Analysis showed that the optimum concentration of KPT EC for the control of the larvae of P. rapae on summer cabbage was 50 mg/kg.