Effects of Temperature and Prey Density on Survival, Development, and Feeding Rates of Immature Typhlodromus pyri (Acari: Phytoseiidae)

Offspring of overwintering female Typhlodromus pyri Scheuten were reared on leaf disks and fed larvae of European red mite, Panonychus ulmi (Koch). In this study, T. pyri nymphs killed fewer prey than did T. pyri in other studies where the predators were reared on artificial substrates such as gelatin capsules. Nymphs showed a type II functional response to prey density: as prey density increased, kills increased at a decreasing rate to a plateau of three to four prey per day. Maximum rates of kill were a quadratic function of temperature over the range 18–26°C. There were significant differences between the sexes in feeding rates but not in rates of development. Rates of development of eggs and larvae and from egg to adult were an exponential function of temperature. Nymphs that ate less than one prey per day had reduced rates of development and survival. Individuals not given any prey survived only a few days as protonymphs. The susceptibility of nymphs to food shortages emphasizes the importance of alternative sources of food (pollen, fungi, other mites) to T. pyri when spider mites are scarce. Temperature responses of this Canadian strain of T. pyri differed from responses reported in western Europe: rates of development from egg to adult were higher at temperatures 20°C.