COMPARISON OF THE RESPONSES OF 2 PREDACEOUS MITES, TYPHLODROMUS-PYRI AND ZETZELLIA-MALI, TO VARIATION IN PREY DENSITY

The ability of a predator to respond to prey density in a patchy habit at has been the focus of much study in biological control systems and elsewhere. Here we look at the response of two species of predatory mi te commonly found in commercial apple orchards, Typhlodromus pyr Scheu ten and Zetzellia mall Ewing. The two species differ in several charac teristics: T. pyri is a more successful biological control agent, is m ore mobile, has a slightly narrower breadth of diet and prefers the ta rget prey, Panonychus ulmi Koch. We measured residence time as a funct ion of prey density, both under field and laboratory conditions. Both predators showed a wide variation in behaviour; however, Z. mali incre ased residence time in response to the presence of prey, while T. pyri did not show a significant response. Both predators usually left a pa tch before all prey were consumed. Patterns from the field and laborat ory were similar, although residence time was shorter under field cond itions.