Landscapes provide ecosystem services to agricultural systems by supporting insect predators of crop pests, a service valued at $US 4.5 billion. Habitat management is the practice of providing resources to beneficial insects in cropping systems, often in the form of flowering strips. However, the potential for flowering strips to increase biocontrol depends on the existing abundances of predators in the landscape, and highly simplified landscapes may support fewer predators than more diverse landscapes. To test the effect of landscape characteristics on the success of habitat management, in 2008 and 2009 we measured predator abundance and aphid suppression at soybean fields with and without flowering strips across a range of landscape diversity measured as Simpson’s D. Predators were measured on yellow sticky traps. Aphid suppression was measured by comparing aphid numbers on plants from which predators were excluded to numbers on plants to which predators had access.
Results/Conclusions
Although lady beetles were attracted to flowering strips, this did not translate into differences in lady beetle abundance or aphid suppression in fields adjacent to strips vs. control fields. Predators dramatically suppressed aphids in all sites. Additionally, there were no significant effects of landscape diversity on aphid suppression, although lady beetle communities varied with measures of landscape composition and diversity. The high rates of biocontrol services across all sites in conjunction with landscape effects on lady beetle communities suggest that different habitats may be supporting different coccinellid species that are equally effective in aphid suppression, resulting in the aggregate abundance of coccinellids and overall biocontrol services being stabilized across Michigan landscapes.
