Abstract
Spider mite densities were low in pear orchards left untreated with pesticides for several years. The year following discontinuance of sprays, the two-spotted spider mite, Tetranychus urticae Koch, caused some defoliation but in subsequent years was not found in destructive numbers. Densities of the European red mite, Panonychus ulmi (Koch), increased until the 4th year after summer sprays were no longer applied. The principal agent in spider mite control was thought to be a phytoseiid, Typhlodromus occidentalis Nesbitt. Attempts were made to increase the number of T. occidenlalis in commercial pear orchards by reducing the rate of azinphosmethyl used for summer control of the codling moth, Laspeyresia pomonella (L.). A rate of 0.5 lb AI/acre allowed predator’s survival and gave good control of the moth, Summer oil was added for suppression of the European red mite. Conversion from a standard program, which included several synthetic acaricides, to the integrated program resulted in economic injury from spider mites the 1st year, but in the 2nd and 3rd years the predaceous phytoseiid held the two-spotted spider mite below injurious levels.
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