GENETICALLY-ENGINEERED VIRAL INSECTICIDES - NEW INSECTICIDES WITH IMPROVED PHENOTYPES

Baculoviruses are natural pathogens of insects which have been used as biopesticides. In contrast to many chemical agents, baculoviruses aff ect only a limited number of insects and so can be used to target part icular insect species. Unfortunately, unless the host receives a very high virus dose, the insect continues to feed and causes damage to cro ps, because the virus takes several days to kill it. This lag is unacc eptable in the protection of many crops, especially where cosmetic dam age seriously reduces the value of a crop (e.g. fruit). Strategies hav e been devised recently to circumvent this problem. The baculovirus ge nome has been modified, using genetic engineering techniques, to incor porate foreign genes encoding insect-specific toxins, or hormones or e nzymes. Expression of some of these genes in the virus-infected host i nsect has been shown to reduce both the feeding damage to crop plants and the time taken to kill the insect pest. The current status of this developing field is described, together with an assessment of the pos sible risks involved in using such genetically modified agents in the environment.