EFFECT OF BACILLUS THURINGIENSIS ON THE EGG STAGE OF PLUTELLA XYLOSTELLA

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.