Ecosystem Trophic Complexity and Densities of the Willamette Mite, Eotetranychus Willamettei Ewing (Acarina: Tetranychidae)

Metaseiulus occidentalis (Nesbitt), a predatory mite, is better able to regulate low densities of willamette mites, Eotetranychus willamettei Ewing, in more complex communities. Willamette mite populations fluctuate more widely in amplitude in simple communities or where monoculture is practiced. Weedy grasses associated with grapevines increase chances for reliable and stable spider mite population control because potentially capable predators are maintained well dispersed in the community by the presence of alternate prey.