苏云金杆菌对小菜蛾卵的生物活性

EFFECT OF BACILLUS THURINGIENSIS ON THE EGG STAGE OF PLUTELLA XYLOSTELLA

在室内２５℃下以浸渍法测定苏云金杆菌（Ｂｔ）对小菜蛾卵的生物活性。结果表明，Ｂｔ对卵的孵化率没有影响，但可导致初孵幼虫死亡。用大田常用浓度处理小菜蛾卵，初孵幼虫死亡率比对照提高约２０％～４０％。不同卵龄、Ｂｔ浓度、处理时间的试验结果表明，初孵幼虫死亡率随Ｂｔ制剂浓度增高而上升，随处理时卵龄增加而下降。

In the laboratory, effect of Bacillus thuringiensis Berliner on the egg stage of diamondback moth, Plutella xylostella, was studied by dipping the eggs directly into Bt suspension, and the rate of hatching and survival of the newly hatched larvae were observed. The Bt tested was a liquid formulation of 2500IU/mg produced commercially by the Hubei Bt Centre. The results indicated that Bt applied to the eggs did not affect egg hatching but cause substantial mortality of newly hatched larvae. With the concentration recommended for field application, eggs treated with Bt usually caused 20% 40% mortality of the newly hatched larvae. Rate of mortality increased with increase of Bt concentration and decrease with ageing of eggs treated, but did not vary with the duration of dipping within the range of 5 60s.