Bt农药对“桂蚕一号”家蚕毒性的测定

Measurement of Toxicity of Bt Preparationon "Guican NO.1"Silkwormvariety

采用浸叶饲喂法,测定了Bt农药对广西现行夏秋用家蚕品种"桂蚕一号"的毒性。结果显示:添食Bt农药浓度越高,家蚕的死亡率越高,且随着感染时间的延长,对家蚕的LC50也越小;对3龄和5龄家蚕72h的持续毒性LC50分别为32.37mg/L和358.04mg/L,其相对毒性比接近11:1,说明小蚕比大蚕较为敏感。因此,建议在蚕区其他作物上应谨慎用Bt农药,以减少和避免对桑蚕业安全生产的威胁。

Toxicity of Bt WP to larvae of Guican No.1 ,which is a normal variety of Bombys mori.L, reared customarily in autumn and summer in Guangxi region,was measured by dipped-leaf feeding on. The results showed that the higher the density was,the higher the morality was,and the half lethal concentration （LC50） was lower as the time continued; The LC50 against the third instar silkworms and the fifth instar ones were 32.37 mg/L and 358.04 mg/L respectively,and the proportion of their LC50 was 11 ： 1 ,which indicated that the small silkworms were more susceptible than the big ones. Therefore,there is a suggestion that Bt WP should be applied carefully in cultivating-silkworm area and on sericulture so that the serious threat on security of sericulture should be decreased or avoided.