Population Dynamics Of The Main Pests And Their Natural Enemies In Bt-cotton And Their Integrated Control Techniques

The diseases and insect pests in cotton fields have greatly changed because of planting Bt-cotton since 1990's. For lacking of the effective pests control techniques in practice, it was necessary to take some measures to resolve these problems.1. This paper dealt with the outbreak characteristics and the population dynamics of the main insect pests and their natural enemies, such as Helicoverpa armigera, Aphis gossypii, Lygus lucorum, Bemisia tabaci, red spiders mites, ladybird beetles, green lacewings, beneficial spiders, and main diseases, Fusarium oxysporium and Verticillium dahliae, on Bt-cotton based on six year's investigations and experiments, which provided the foundation for taking measures to control pests and diseases of Bt-cotton. The results demonstrated that Bt-cotton had no effect on the number of H. armigera egg in the fields, but it showed high resistance to H. armigera larvae, and the quantity of H. armigera larvae were obviously less than that on Bt-cotton; the original subordinate pests, such as L. lucorum and B. tabaci etc. gradually became the main pests on Bt-cotton; A. gossypii and the red spider mites still damaged heavily, and the occurrence trend of many pests was consistent with that on non Bt-cotton; the number of beneficial spiders increased slightly, and ladybird beetle, green lacewing had no changes compared with those on non Bt-cotton.2. The difference of community characteristics of the main pests and their natural enemies on Bt cotton and non Bt-cotton was studied. The community indices of the main pests and natural enemies in different parts of Bt-cotton and non Bt-cotton plants were analyzed. The main difference was that H. armigera was the main pest on non Bt-cotton, but it became the subordinate pest on Bt cotton; the community stability of Bt-cotton was superior to that of non Bt-cotton; the best community stable phase on Bt-cotton was achieved earlier than that on non Bt-cotton.3. Comparative studies were made on the niches of the main pests and...