Biological Control of Thrips palmi (Thysanoptera: Thripidae) with the Predatory Bug, Wollastoniella rotunda (Hemiptera: Anthocoridae) on Greenhouse Eggplant in Winter

To evaluate the effectiveness of the predatory bug, Wollastoniella rotunda Yasunaga et Miyamoto, against Thrips palmi Karny on eggplants in greenhouses, we conducted experiments over two growing seasons. In the first experiment, 71 adults of W. rotuuda were released in Novernber 1997, and the release ratio was 1:4 (adult bug: thrips) for prey density of 0.06 thrips per leaf. This release was successful in controlling a T. palmi population that had such a low density at the release time. In the second experiment, a total of 180nymphs of W. rotuuda were released three times in October and November 1998. These releases were also effective in controlling a T. palmi population that had a low density (0.15 thrips per leaD on the first release, and the release ratio of nymphal bugs to thrips was 1:2. Based on these results, we conclude that W. rotuuda could be effective as a biological control agent against T. palmi in winter greenhouses.