Quiring, Donald M.J.

The potential of Dicyphus hesperus Knight as a predator of greenhouse whitefly, Trialeurodes vaporariorum (Westwood), and two-spotted spider mites, Tetranychus urticae Koch, was assessed in the laboratory and in a tomato greenhouse. D. hesperus adults fed readily upon both pest species in the laboratory, and nymphs completed development from egg to adult on either whitefly or mites. Whitefly, however, were a superior food for growth and development of D. hesperus compared to mites. Development time was shorter and resulting adult body size was larger for nymphs reared on whitefly compared to those reared on mites. In a greenhouse release, adults oriented to and oviposited on whitefly-infested sentinel plants but did not orient to mite-infested sentinel plants. D. hesperus adults oviposited on greenhouse tomatoes and their progeny completed development in a greenhouse in which both whitefly and mites were present. The results are discussed as they relate to the use of D. hesperus for biological control of pests of greenhouse vegetables.

Evolutionary and ecological transitions from carnivorous to omnivorous feeding may be constrained by the ability of the animal to cope with disparate types of foods, even if preadaptations for such behaviour exist. The omnivorous true bug, Dicyphus hesperus (Hemiptera: Miridae) requires both animals (small, soft-bodied insects) and plants in its diet and obtains the majority of its dietary and metabolic water from plant feeding. Serrations on the lateral margins of the mandibular stylets wear with age, and this wear is exacerbated when the insects feed on plants compared to those provided free water and no plants. D. hesperus that feed on plants attack fewer prey but consumed similar amounts of prey tissue compared to individuals that were provided free water. Although others have shown mandible wear for plant-chewing animals we show for the first time that plant feeding can impose similar wear on plant-piercing animals as well.