DISPERSION, SAMPLING, AND POTENTIAL FOR INTEGRATED CONTROL OF 2-SPOTTED SPIDER-MITE (ACARI, TETRANYCHIDAE) ON GREENHOUSE ROSES

Five applications of abamectin applied at a concentration of 12 ppm an d at 3- to 5-d intervals as full canopy sprays provided effective cont rol of Tetranychus urticae Koch on greenhouse roses, but also eliminat ed a biological control agent, Phytoseiulus persimilis Athias-Henriot. However, abamectin applications confined to the upper portion of the canopy (from where the marketed portion of the crop is taken) provided chemical control of spider mites in the upper canopy. The lower canop y supported a rapidly decreasing spider mite population and a slightly increasing population of P. persimilis. These results show the potent ial for integration of biological control of T. urticae with chemical control of T. urticae and other pests of greenhouse roses. Dispersion of T. urticae was determined using Taylor's power law, and fixed-preci sion-level sampling plans were developed for estimating population den sities. Use of binomial sequential sampling plans, using differential action thresholds for upper and lower canopies, are proposed for monit oring T. urticae in commercial rose production. The potential for cont rol of T. urticae through pest population monitoring and integration o f chemical and biological control is discussed.