DOES PESTICIDE-INDUCED ACTIVITY OF 2-SPOTTED SPIDER-MITE (ACARI, TETRANYCHIDAE) REALLY CONTRIBUTE TO POPULATION INCREASES IN ORCHARDS

The effect of pesticides on the population density, dispersion, and activity of Tetranychus urticae was investigated. In the laboratory, permethrin, phosmet and phosalone significantly increased the time spider mites were active, whereas the pesticide azinphosmethyl did not significantly affect activity. In the field, by 12d after pesticide application, mite populations on all pesticide-treated trees were significantly higher than those on the water-sprayed control trees. Pest resurgence is probably not a result of increased mite activity, but is instead related to a pesticide's ability to stimulate mite physiology, either directly or indirectly, through changes in host plant nutritional value. -from Author