However, attempting to enhance conservation biological control through increasing cropping diversity may become less effective with an increase in pest diversity and intraguild predation among natural enemies; thus modifying habitats has indeed been found to have neutral and negative impacts on the target pest insects under some circumstances (Straub et al., 2008; Winkler et al., 2010). Therefore, carefully planned management of diversity of crop plants is important to optimize activity of natural enemies and reduce pest density (Landis et al., 2000).