Seasonal changes and infestation sites of the chillie thrips, scirtothrips dorsaris (thysanoptera: Thripidae) on grapes

Abstract

Seasonal changes and infestation sites of the chillie thrips, Scirtothrips dorsaris were investigated on two cultivars of grapes, Neo Muscat and Muscat Bailey A, in 1988 in Okayama. Censuses were conducted by random sampling of shoots and trapping. The infestation occurred from June to September. Seasonal changes in density had two peaks in July and August. The occurrence of the thrips was most abundant on lateral shoots in Neo Muscat, and on the tops of leaves and canes in Muscat Bailey A. The density of the thrips on Neo Muscat was higher than that on Muscat Bailey A. The density on fruit clusters was low in both cultivars throughout the period although severe injury occurred on fruits. The density on each part of the different nodes of shoots was also investigated. The density was high on the top and middle parts of shoots in Neo Muscat, and on the top parts of shoots in Muscat Bailey A. The spatial distribution pattern of the thrips was analyzed by the m-*m regression method. The distributions of both nymphs and adults were contagious in most parts of the shoot. The number of adults caught by the sticky trap was positively correlated with the density of adults on various parts of hosts except for the fruit cluster. Therefore the sticky trap can be used for a rough estimation of the population trend on grapes but not for the injury of fruits. © 1990, JAPANESE SOCIETY OF APPLIED ENTOMOLOGY AND ZOOLOGY. All rights reserved.