Insect communities in greenhouses are often complex, consisting of several pest insects and their predators. Dicyphus hesperus Knight (Heteroptera: Miridae) is currently used as a biological control agent in greenhouses in Canada. Dicyphus hesperus is an omnivorous predator with the potential to suppress several pest species. However, D. hesperus will also prey upon the predators of those pest species. It is postulated that herbivore population suppression will not be disrupted in the presence of D. hesperus if D. hesperus expresses no preference for either prey type (the herbivore or its predator) and/or neither prey type exhibits an advantage in prey defences. This study measured the functional response of D. hesperus for two pest species Trialeurodes vaporariorum and Tetranychus urticae and two specialist natural enemies Encarsia formosa and Phytoseiulus persimilis. In addition, parameters that determine the functional response of D. hesperus by limiting predation (prey mobility, satiation) were examined.

Key words: Dicyphus hesperus, intraguild predation, functional response, prey preference