Movement of Two Species of Tetranychid Mites (Acarina: Tetranychidae) from Border Vegetation to Watermelon Fields

Abstract

The two-spotted spider mite, Tetranychus urticae Koch, and the Kanzawa spider mite, T. kanzawai Kishida, are both key pests on watermelons in Wakayama Prefecture. In many watermelon fields, the predominant species of spider mites on watermelons coincides with those on border vegetation along field margins. The densities of spider mites are higher at the marginal ridges of fields than at the central ridges. This suggests that spider mites disperse from overwintering sites on border vegetation into watermelon fields. Spider-mite populations increased on vetch, Vicia sativa, the main species of border vegetation. As the V. sativa withered, the mites started being trapped by sticky traps set between the watermelon plants and the border vegetation in May, showing that the mites were dispersing from the V. sativa. Herbicide application on border vegetation in early March, two weeks before watermelon transplantating, reduced the spider-mite population in the watermelon fields. © 1992, JAPANESE SOCIETY OF APPLIED ENTOMOLOGY AND ZOOLOGY. All rights reserved.