Species Composition and Seasonal Occurrence of Orius spp. (Heteroptera: Anthocoridae), Predacious Natural Enemies of Thrips palmi (Thysanoptera: Thripidae), in Eggplant Fields and Surrounding Habitats

We investigated the species composition of Orius spp., predacious natural enemies of Thrips palmi KARNY in eggplant fields and surrounding vegetation. At Chikushino, O. sauteri (POPPIUS) was dominant on eggplant, followed by 0. minutus (LINNAEUS) and 0. nagaii YASUNAGA. 0. sauteri also dominated the sample on white clover, while the other two species occurred with an extremely low frequency. In contrast, on Gramineae plants such as rice, forage crops and weeds, 0. nagaii was exclusively dominant, while the other two species were rarely found. These results suggest that the habitats surrounding an agro-ecosystem serve as reservoirs for Orius spp. occurring in eggplant fields. The species composition on eggplant varied with sampling date and locality. In the three IPM fields where selective chemicals were applied, the first peak of abundance on leaves was found in early and mid-July, indicating that Orius spp. adults begin to immigrate into eggplant fields from early June. From results of direct count on leaves and sticky trap data, Orius spp. colonization and subsequent reproduction appeared to be influenced greatly by prey population size.