Initial Survey of Arthropods Found in North Coast Vineyards of California 1

A survey of spider mites and their predators in North Coast vineyards revealed that Tetranychus pacificus McGregor and Eotetranychus willamettei (McGregor) are differentially distributed on the vine and leaves. Metaseiulus occidentalis (Nesbitt) is the most abundant predator and the only one with distribution coinciding with that of the spider mites occurring on foliage. Other predators, notably mites of the families Bdellidae and Anystidae, may be important factors limiting the number of spider mites successfully overwintering in the bark fissures. Of eight vinifera varieties plus wild grape sampled, ‘Sauvignon vert’ was the most susceptible to attack by spider mites and supported the highest densities.