Testing the intermediate landscape complexity hypothesis for augmentative biological control

Biological control of pests by natural enemies is dependent not only on local conditions, but also on the surrounding landscape and the interplay between both spatial scales. The intermediate landscape complexity hypothesis states that on farm scale management such as the creation of habitat for natural enemies should be more successful to increase biocontrol services at landscapes of intermediate complexity. However, it is still unclear how augmentative biological control as a local practice is affected by the landscape context and the naturally occurring enemy communities. In this study, we provide empirical evidence of how the effect of augmentative biocontrol by the spined soldier bug, Podisus maculiventris (Hemiptera: Pentatomidae), is influenced by the surrounding landscape. We selected pairs of cabbage fields (one with augmentative biological control and the other unmanaged) along a landscape complexity gradient to determine the effects of augmentative releases on biocontrol levels and consequent plant damage and yield. We also used sentinel preys and surveillance video cameras to identifty the natural enemies that were attacking lepidopteran pest in the field and to determine their efficiency rates. Understanding interactions among natural enemies and landscape complexity will help us develop a sustainable management strategy based on augmentation of a generalist predator to control cabbage pests while maintaining high yields and profits.