Landscape scale pest management: Approaches for understanding habitat function

While IPM has traditionally focused on the field scale, two observations have triggered interest in developing IPM at larger spatial scales. First, mobile pests do not recognize field or farm boundaries. Second, some landscapes appear less prone to invertebrate pest infestations than others, suggesting that there are features that may be managed to create more pest suppressive landscapes. Landscape complexity has been shown to increase the ecosystem service of pest suppression, although the mechanisms responsible remain elusive. Using a range of approaches including survey, large-scale experimentation and GIS from two production systems, cotton-grain in the Darling Downs, and vegetables in the Lockyer Valley, QLD, we'll explore the link between surrounding habitats, pest and beneficial insect dynamics and pest suppression. In the cotton/ grain systems, we show that natural enemies (as well as some pest species) use native vegetation as reproduction habitat, move between native vegetation and crops, and colonize crops. We also show that some pest species are more strongly suppressed by natural enemies in crops near native vegetation than further away, and that native plants have higher predator : pest ratios compared to crops. In the vegetable system, we tested the effect of earliness of predator impacts on the suppression of pests in 19 vegetable landscapes that differ in landscape complexity. We found that predators have a significant impact on pests, but only some landscapes contributed predators early. Most of the variation in pest suppression was explained by the amount of Lucerne (alfalfa) around the focal fields up to 2 km. Lucerne was shown to be good habitat for predators, but high predator numbers explained most of the variation in high pest numbers in focal fields. This paradox demonstrates the challenge of managing for pests and pest control services at multiple spatial scales. We'll conclude by showing how these findings can contribute to guidelines for IPM at the field, farm and landscape scale