Tests have been conducted for several years with the support of the table grape, raisin, and wine industries, on pest management practices for spider mites and associated pests in the southern San Joaquin Valley. A major part of this effort has emphasized the correction of a spider mite imbalance in vineyards. Willamette mite (Eotetranychus willamettei Ewing) and Pacific mite (Tetranychus pacificus McGregor) had become difficult and expensive to control, and over-emphasis on chemical control programs was making the situation worse. Grape growers in Fresno County alone had been spending approximately one million dollars annually for spider mite control, and considerable vineyard damage still occurred. Moreover, it was observed that vineyards with histories of little or no pesticide use had few, if any, spider mite problems.

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