Approaches And Mechanisms For Improvement Of Nucleopolyhedroviruses

Nucleopolyhedroviruses (NPVs) have received considerable attention because they provide attractive alternatives to chemical insecticides and have the potential to form components of integrated pest management (IPM) programmes due to their efficacy, specificity, production of secondary inoculums, and the lack of non-target effects. However, when compared to chemical insecticides, NPVs have a number of drawbacks. The narrow host range of NPVs generally restricts their effectiveness against the complex of insect pests that usually attack a given crop. Furthermore, the slow speed of action allows pests to continue their damage longer, even the ultimate efficacy against a given insect may be comparable with chemical insecticides. Therefore, although many NPVs have been proved to be potential to control insect pests, fewer of them are registered as insecticides, and successfully used in practice.For improvement of NPV, a lot of work has been done. However, there is little reports on the S1NPV which infests Spodoptera litura. Common cutworm, Spodoptera litura F. and beet armyworm, Spodoptera exigua F. (Lepidoptera: Noctuidae) are two important insect pests of many agricultural crops, which have developed resistance or high tolerance to most of the available chemical insecticides. NPVs are thought to be the promising alternatives to chemical insecticides and could be readily integrated into IPM programs to overcome insecticide resistance and reduce the use of chemical insecticides. In this paper, the approaches and their mechanism for improving the virulence and killing speed of NPV against S. exigua and S. litura were studied.1. Approaches for improvement of NPVsApproaches for improvement of NPVs were searched by testing the synergism between different virus species, different NPV isolates, and the combinations of NPV and insect growth regulators. The effect of host alternation and propagation on the virulence of NPV was also studied. The results were summarized as follows: 1.1 Synergistic effect of Xestia c-nigrum granulovirus (XcGV) on NPVs XcGV was tested for its ability to increase the NPV infection of the larvae of S. litura...