Towards a Healthy Control of Insect Pests: Potential Use of Microbial Insecticides

Different microbial insect pathogens have been used as insecticides for the control of different insect pests in agriculture and also for the control of insects that are vectors of important human diseases. These microbial pathogens include bacteria, viruses and fungi. These microbes differ in their insect specificity and mode of action. Nevertheless, insecticides based on these microbial insect pathogens have had a limited use in comparison to chemical insecticides. In this chapter we will revise the potential use of some of these microbial pathogens highlighting their mode of action, insect specificity, risk assessments for the environment and also key application practices to assure the development of more healthy insect control products. Bacterial pathogens rely on different virulence factors to invade their hosts. Among these, bacterial toxins are by far the most important virulence factors. Some δ-endotoxins produced by Bacillus thuringensis, have been expressed in transgenic crops resulting in the reduction of the use of chemical insecticides. Other insecticidal toxins from other bacterial species are likely to provide additional tool for insect control in agriculture. Although different viruses and fungi have the potential for use as insect control, their wide use has been limited by their narrow spectrum of action, application practices and in some cases low susceptibility by older larval instars. However, the genetic manipulation of their genomes by the introduction of insect toxins or catabolic enzymes has been shown to significantly improve their insecticidal activity and their potential for wider use as insect control agents.