植物性杀虫剂苦皮藤乳油控制菜青虫有效剂量的研究

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２４．７８ｍｇ／ｋｇ，７２．５５ｍｇ／ｋｇ，１２４．３５ｍｇ／ｋｇ，３２１．２１ｍｇ／ｋｇ，１２４０．４２ｍｇ／ｋｇ。田间药效试验表明一次施药５０ｍｇ／ｋｇ和１００ｍｇ／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

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

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.