Biological Control of Apple Mites by Mixed Populations of Metaseiulus occidentalis (Nesbitt) and Typhlodromus pyri Scheuten (Acari: Phytoseiidae)

Mixtures of Metaseiulus occidentalis (Nesbitt) and Typhlodromus pyri Scheuten inoculated into apple trees gave as good or better biological control of European red mite Panonychus ulmi Koch and twospotted spider mite Tetranychus urticae (Koch) than did similarly sized populations of either predatory mite alone. In mixes, M. occidentalis increased more rapidly and achieved higher densities at midseason when prey were abundant than did T. pyri, which persisted longer and provided more predation at the end of the growing season. Both species alone gave near equal control of P. ulmi . Control of twospotted mite by M. occidentalis was always excellent. Sometimes, T. pyri did not control T. urticae before it reached damaging levels. These mites appear to be complementary biological control agents. Their management in mixed populations is discussed.