Developments Toward Biological Control of Cyclamen Mite on Strawberries in California

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Abstract
Population studies of the cyclamen mite, Tarsonemus pallidus Banks, and the laelaptid mite, Typhlodromus reticulatus Oud. and/or T. cucumeris Oud., predatory on it in field strawberries in California, were conducted for a period of 3 years. The purpose was to appraise the degree and consistency of any controlling action under a variety of conditions and to evaluate the possibilities and determine the means of utilizing natural enemies to better advantage. Results were obtained from 20 pairs of field plots in which 1 plot of each pair was kept predator-free by treatment with Parathion and 1 had predators. These included plots in 2nd, 3rd-, and 4th-year berries of 6 different varieties in the plantings of many different operators throughout the Santa Clara County strawberry district. A longer-term study of populations on greenhouse berries and 1 test involving hand-removal of the predators were also included, as were tests on the relative toxicity to the predator of several commonly used acaricides. The field population studies were consistent and showed that the predators exert effective control of the cyclamen mite in 3rd- and 4th-year fields in this area when their activities are not inhibited by detrimental chemical treatments used for control of other pests. Control in 2nd-year fields was somewhat erratic due, it is felt, to the lag in appearance of predators and to the more vigorous treatment practices which are applied to the 2nd-year crop. The long-term greenhouse study verfied the field results and showed how well the predator can control its host at a consistently low level. Results from tests on hand-removal of the predators removed any objection to the interpretations on the basis that parathion might in itself favor increase of cyclamen mites. Both hand-removal and chemical removal of predators resulted in cyclamen mite increases.

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