2016 Volume 60 Issue 4 Pages 171-178
The local density of natural enemies, which provide biological control, can be affected by the surrounding landscape and by local field management. We examined how landscape factors and non-selective insecticides influenced the abundance of predatory bugs of the genus Orius, which provide effective biological control on eggplant, from June to September 2013. We investigated the numbers of these bugs in 13 eggplant fields across four regions of Nara prefecture, Honshu, Japan. Areas of different land-use types around the fields were estimated from GIS data in circular buffer zones with radii ranging from 100 to 1,000 m（intervals of 100 m）. Using a generalized linear model and Akaike’s Information Criteria, we analyzed the effects of landscape element, landscape heterogeneity and use of non-selective insecticides on the abundance of Orius spp. Landscape elements within a 200-m radius affected abundance: the abundance of Orius spp. was higher in landscapes with a mixture of urban and agricultural areas than in landscapes dominated by forest. On the other hand, non-selective insecticides did not affect the abundance of Orius spp. This result suggests the importance of landscape factors in determining the local abundance of Orius spp.
