４種天敵を利用した夏作メロンにおける主要害虫の体系防除の試み

Abstract

An attempt at integrated control of four major insect pests, the cotton aphid Aphis gossypii, the two-spotted spider mite Tetranychus urticae, the melon thrips Thrips palmi and the silverleaf whitefly Bemisia argentifolii, was conducted for greenhouse melon cultivated in the summer season, from May to July, utilizing four species of natural enemies, Chrysoperla carnea, Phytoseiulus persimilis, Orius sauteri and Encarsia formosa. The aphid population was effectively controlled at a low density when C. carnea was released 5 times at about 2 week intervals starting from 19 days after planting melon seedling with a ratio of one predator to 20 prey. The spider mite population was also controlled at a low density by releasing P. persimilis 2 times, on the 26th and 37th days after planting, with a ratio of one predator to 20 prey. No damage was caused by these two pests in he released plot, but in the non-released plot severe damage was observed. O. sauteri was released at a ratio of one to 20thrips on the 37th day after planting, but the effect was not evaluated because the thrips population in the non-released plot was also at a ow level during the experiment and no damage was caused. The whitefly population was controlled at a level of one fourth or less of the non-released plot and no economic damage was caused when E. formasa was released 4 times at about 2 week intervals from he 24th day after olantine. with a rate of 100 mammies per 40 plants.