Optimal Foraging Behavior and Efficient Biological Control Methods

Abstract

Insect parasitoids have been used for the biological control of insect pests through classical importations for the control of invasive phytophagous species, through seasonal or inundative releases for short-term suppression of indigenous or invasive pests, and through conservation of parasitoid activity by the provisioning of resource subsidies and alteration of management practices. In all cases, success in the suppression of a pest is dependent upon the behavioral decisions made by the parasitoid in searching for and parasitizing hosts. For example, in the case of classical biological control, patch choice decisions that maximize parasitoid fitness will tend to increase its regional impact, leading to greater suppression of the pest and success in biological control. In contrast, for augmentative biological control, the goal is to provide local pest suppression and behavior that maximizes fitness might, for example, lead parasitoids to abandon local patches of their hosts before the pest has been suppressed to the desired level. Thus, the behavioral ecology of insect parasitoids is central to the successful implementation of biological control programs. We explore how optimal foraging effects the suppression of global pest densities in a metapopulation context and to what extent the physiological condition and behavioral decisions of foraging parasitoids are likely to influence establishment and impact in classical biological control. In the case of inundative biological control, we discuss the trade-off between optimal foraging behavior and the level of pest suppression at a local scale and consider the use of chemical attractants and arrestants to increase parasitoid activity and patch time allocation. We also discuss the influence of host size and quality, and sex ratio (Wolbachia infection) on parasitoid mass rearing. Finally, the influence of nectar subsidies on parasitoid foraging behavior and host suppression is considered in the context of developing more efficient methods for conservation biological control. 1 Optimal foraging behavior and efficient biological control methods Nick J. Mills and Eric Wajnberg 4 N.J. MILLS AND E. WAJNBERG