can kill rapidly will allow them to compete more effectively with classical pesticides. To increase the ability of baculoviruses to kill early, research to insert specific genes into the baculoviral genome is under way. These genes will serve as toxins or disrupters of larval development. Among the proteins being tested for exploitation are Bt endotoxin (which failed to improve the virus), juvenile hormone esterase, prothoracicotropic hormone (PTTH), melittin, trehalase, scorpion toxin, and mite toxin (Bruce Hammock, University of California, Davis, November 12, 1998, personal communication). The knowledge of the molecular biology of viruses has also promoted interest in modifying and improving baculoviruses with regard to host range and virulence.

The regulatory process that will be applied to recombinant baculoviruses is not yet clear. The recombinant virus system makes it possible to exploit a variety of proteins, including insect enzymes and hormones and proteins from other organisms. The recombinant viruses that will probably be commercialized first in the United States are the ones that carry genes expressing insect-selective nerve toxins, which are undergoing intensive safety and efficacy testing. In the United States public concern has not been voiced with regard to the safety of these viruses. However, objections have been raised in England as to the use of toxin genes in baculoviruses.

The growth and success of baculoviruses as commercial insecticides will depend on reducing production costs, developing practical and effective formulations, optimizing field performance, overcoming regulatory obstacles, and educating users and the public on their safety. To enable development of more economical and effective products, R&D efforts should focus on making improvements in baculovirus production, formulation, and application technologies in conjunction with genetic engineering of the viruses to enhance their kill rates and broaden their host range.

Entomopathogenic Fungi

Over 500 fungi are regularly associated with insects; some cause serious disease in their hosts, but few have been used commercially as control agents. Because of their dependence on specific environmental factors, such as relative humidity, fungi can be useful tools in IPM, especially as complements to other products. Fungi infect a broader range of insects than do other microorganisms, and infections of lepidopterans (moths and butterflies), homopterans (aphids and scale insects), hymenopterans (bees and wasps), coleopterans (beetles), and dipterans (flies and mosquitoes) are quite common. In fact, some fungi have very broad host ranges that encompass most of those insect groups. That is true of Beauveria

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