Canopy management is an integral component of wine grape production. Several factors related to canopy architecture, including microclimate and pesticide penetration, can affect pest control. However, the impact of canopy structure on pest control is poorly understood. We have been investigating spider mite biocontrol by specialist- and generalist-feeding phytoseiid mites in Washington wine grapes. In 2003, we conducted replicated field experiments investigating effects of chlorpyrifos and sulfur on mite densities. Vine stature and associated microclimatic differences appeared to influence mite dynamics and response to chemical treatments. Thus, we are currently investigating impacts of canopy structure on the efficacy of spider mite biocontrol by chlorpyrifos and generalist phytoseiid mites.