Understanding how parasitoids balance food and host needs: Importance to biological control

Adult parasitoids must not only find hosts for reproductive purposes but also locate food to meet their short-term nutritional needs. A knowledge of how parasitoid females deal with the often competing needs for these two vital resources is essential for understanding their foraging strategies. Studies show that avail ability and accessibility of food sources, such as nectar or honeydew in a target area, strongly affect parasitoid retention and host-finding efficacy. For parasitoids to maintain high reproductive success it is important that disruption of their host foraging process is minimal so that most of their time and energy can be allocated to finding hosts. The use of olfactory and visual cues from plants, usually enhanced by learning, helps minimize this disruption and plays important and sometimes interacting roles in their searching for food and hosts. Thus, the provision of food sources such as floral and extrafloral nectar by plants along with associated foraging signals plays a crucial role in the tritrophic interplay among plants, herbivores, and parasitoids. A broader understanding of tritrophic level interactions that encompasses parasitoid food considerations can enhance our ability to design effective biological control strategies. Herein, we discuss how the internal state of parasitoids along with characteristics of their foraging environment, can influence their ability to find food and consequently affect their parasitizing efficiency. Suggestions are made for maximizing food-finding efficacy to improve biological control with parasitoids.