POPULATION STUDIES OF PHYTOPHAGOUS MITES AND PREDATORS ON APPLE IN SOUTHWESTERN QUEBEC

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Abstract
Ecological studies, undertaken to determine the fluctuations of phytophagous mites and predators in apple orchards, were conducted in 1955, 1956, and 1957 at Rougemont, Que., in two plots sprayed only with fungicides for the control of apple scab, Venturia inaequalis (Cke) Wint., and in a third one sprayed, in addition to fungicides, with all insecticides needed for the control of destructive insects. Phytophagous mites were more numerous in the plot sprayed with insecticides than in plots sprayed only with fungicides, and densities of the mites in the latter plots were inversely proportional to densities of predators. A similar relationship existed in the insecticide plot between the amount of chemicals used and numbers of predators present. The principal mite predators were Typhlodromus rhenanus (Oudms.), most effective against the two-spotted spider mite, Tetranychus urticae Koch, and Mediolata mali (Ewing), most effective against the European red mite, Panonychus ulmi (Koch).