Abstract: Objective To evaluate the toxic effect of Bacillus thuringiensis var. israelensis（Bti）wettable powder against Ae? des，Culex and Anopheles larvae. Methods The biological assay was applied to test the lethal concentration of 50%（LC50 ）of Bti wettable powder against Aedes，Culex and Anopheles larvae. Results The LC50 （s）of Bti wettable powder against Aedes albopictus， Culex pipiens pallens and Anopheles sinensis larvae were 0.104，0.160 μg/ml and 0.324 μg/ml，respectively；its biological poten? cies against them were 0.125，0.192 IU/ml and 0.389 IU/ml，respectively. The LC50 （s）of continuous contact of Bti wettable powder with An. sinensis stage Ⅲ larvae for 1，2 d and 3 d were 0.324，0.092 μg/ml and 0.032 μg/ml，respectively，and its biological po? tencies were 0.389，0.110 IU/ml and 0.038 IU/ml，respectively. The LC50 （s）of the bacteria against An. sinensis stageⅠ， Ⅱ，Ⅲ，Ⅳ were 0.024，0.137，0.324 μg/ml and 0.450 μg/ml，respectively，and the biological potencies were 0.029，0.164，0.389 IU/ml and 0.540 IU/ml，respectively. Conclusion Bti wettable powder has a good toxicity to Aedes，Culex and Anopheles larvae，espe? cially for the latter two. It is better to apply the bacteria at the early stage of mosquito larvae.

Key words: Bacillus thuringiensis var. israelensis（Bti）； Mosquito larvae； Toxic effect

摘要： 目的 目的 研究苏云金杆菌以色列变种 （Bti） 可湿性粉剂对伊蚊、 库蚊和按蚊幼虫的毒杀效果。方法 方法 采用生物测定 法， 测定Bti可湿性粉剂对白纹伊蚊幼虫、 淡色库蚊幼虫和中华按蚊幼虫的毒杀效果， 计算半数致死浓度 （LC50 ）。结果 结果 Bti 可湿性粉剂对Ⅲ龄白纹伊蚊幼虫、 淡色库蚊幼虫和中华按蚊幼虫的LC50 分别为0.104、 0.160 μg/ml和0.324 μg/ml， 效价 分别为0.125、 0.192 IU/ml和0.389 IU/ml； 连续接触中华按蚊Ⅲ龄幼虫 1、 2 d和 3 d的LC50分别为0.324、 0.092 μg/ml和0.032 μg/ml， 效价分别为0.389、 0.110 IU/ml和0.038 IU/ml； 对中华按蚊Ⅰ、 Ⅱ、 Ⅲ龄和Ⅳ龄幼虫的LC50分别为0.024、 0.137、 0.324 μg/ml和0.450 μg/ml， 效价分别为0.029、 0.164、 0.389 IU/ml和0.540 IU/ml。结论 结论 Bti对3种蚊虫幼虫均有较好的毒杀效 果， 但对伊蚊和库蚊幼虫效果更好， 且幼虫虫龄越小， 毒杀效果越好。

关键词: 苏云金杆菌以色列变种； 蚊虫幼虫； 毒效效果