Interactive-web of Factors Governing Effective Natural Enemy Foraging Behavior: Overview of Food Resources as a Critical Component

Effective biological control of pests is determined by the abundance, retention and searching efficacy of natural enemies. To assure their reproductive fitness, natural enemies such as predators and parasitoids must effectively balance competing resource needs such as an adequate frequency of encounter with prey and hosts for reproduction, requirements of food other than prey and hosts, and other needs such as shelter and mates. The other food requirements consist primarily of short-term nutritional needs and are often separate from the target pest, such as plant nectar in the case of parasitoids. The appropriate quality, adequate availability, and detectability of these non-mutually exclusive requirements in the target area, strongly affect the natural enemy’s retention and pest foraging efficacy. We present a conceptual model of factors determining eventual foraging behavior of parasitoids that would guide empirical studies of the resource needs of parasitoids and other insects. An increased understanding of the interplay of the resource web with the habitat would allow us to leverage this information to design habitat management practices that allow the use of natural enemy species for biological control in a consistent and reliable manner. THE IMPORTANCE OF ADULT FOOD FOR PARASITOIDS The importance of adult food for natural enemy species such as predators and parasitoids has been recognized for decades. Parasitoid species (species that lay their eggs on or in other insect species, eventually killing them) are often used as models of natural enemy foraging behavior because of the relatively direct link between their foraging behavior and reproductive fitness when compared with predator species. Numerous laboratory studies have shown that suitable food sources can substantially increase longevity and fecundity of adult hymenopteran and dipteran parasitoids (reviews in Heimpel et al. 1997; Lewis et al. 1998). It is now appreciated that the consumption of non-host food can influence many other aspects of parasitoid biology such as egg viability, diapause in progeny, foraging decisions, searching