Biological Control of Thrips palmi Karny by Amblyseius cucumeris Oudeman on Melon in Greenhouses

Abstract

Thrips palmi Karny is the most serious pest of greenhouse melon in Japan. The predatory mite, Amblyseius cucumeris Oudeman, was released in melon greenhouses during the summer growing season to control T. palmi. In trial 1, approximately 100 A. cucumeris per plant were released on melon leaves 3 times; 3, 4 and 5 weeks after planting. The density of T. palmi in released greenhouses were 25% of that in the unreleased control greenhouses, and the injury index of leaves was 40% of that in the control 4 weeks after the first release. In trial 2, A. cucumeris was released on soil at the base of each plant. The predatory mites were released 2, 7 and 14 days after planting at a density of 100 mites per plant. The density of T. palmi in released greenhouses was 6% of that in unreleased greenhouses 5 weeks after the first release, and the injury index of leaves was 33% of that in the control 7 weeks after the first release. These results suggest that A. cucumeris was effective in reducing the numbers of T. palmi on greenhouse melon, and that the most effective timing of first release was just after planting.