Abstract
Effects of lateral shoot cutting on population density of the chillie thrips, Scirtothrips dorsalis HOOD, on grape, cultivar Neo Muscat, were investigated in Okayama in 1990, Two experimental plots were designed, with cut or uncut lateral shoots. The numbers of adults and larvae collected by washing were much smaller in the cut plot than in the uncut plot, suggesting that their occurrence on shoots was influenced by the quantity of available resources (lateral shoots). On the other hand, the number of catches with yellow sticky traps was much greater in the cut plot than in the uncut plot. Results suggested that the number of catches reflected the frequency of adult dispersal and that the dispersal was more frequent in the cut plot because of the resource shortage. The number of the trap catches reflected the population fluctuation in each of the two plots, although the regression coefficient (X: the number of adults collected by washing method, Y: catches by yellow sticky trap) was extremely different between the two plots. Degree of damage to the fruit cluster did not differ between the two plots.
