Botanical Insecticides and Antifeedants: New Sources and Perspectives

Although hundreds of plant natural products (allelochemicals) have demonstrated deleterious effects on insects in laboratory bioassays, only a handful of botanical insecticides are currently approved for use in industrialized countries. Two main factors may account for this dichotomy. Firstly, insecticide discovery often relies on bioassays which focus on acute toxicity; as a consequence, important sublethal or chronic effects may be completely overlooked. Secondly, commercialization of botanical preparations for insect control may hinge more on practical concerns (e.g. availability of large quantities, management of chemical variability) than on biological ones (e.g. efficacy, favorable non-target toxicity). Antifeedants continue to attract considerable interest in the research community, but their utility for insect control remains questionable. Potential problems with antifeedants as crop protectants (e.g. interspecific variation) are discussed. However, recent studies suggest that many allelochemicals described as antifeedants in the literature may have a broader range of physiological effects on insects. A more comprehensive program of bioassays used in the screening of plant extracts or isolated compounds may help uncover new plant material that have the potential to be developed into botanical insecticides,