ABSTRACT
Viruses and microorganisms that cause disease in insects have been under evaluation as insecticides for more than a century. Only Bacillus thunngiensis (Bt) has been a commercial success and even so it still represents less than 1 % of insecticide usage worldwide. The development o f recombinant DNA techniques, however, has made it possible to significantly improve the insecticidal efficacy of viruses, bacteria and fungi that attack insects. Here we review the recent literature on advances made with model viral, bacterial and fungal pathogens of insects, showing how the efficacy of wild type pathogens can be improved ten-fold or more using genetic engineering techniques. These advances have been achieved by combining new knowledge derived from basic studies of the molecular biology and genomics o f these pathogens with technical de velopments that enable increased gene expression and the use of genes from other organisms that encode highly specific enzymes and insecticidal proteins to improve efficacy. W ith increasing public concern over the continued use of synthetic chemical insecticides, these new types of biological insecticides offer a range of environmentally compatible options for cost-effective control of insect pests and vectors of disease that continue to plague agriculture and human health.
