Impact of switchgrass (Panicum virgatum) cultivar and cropping system on insect communities and biological control services

Switchgrass (Panicum virgatum) is a perennial C4 grass which has been studied as a dedicated biomass crop.  It is capable of producing high yields while supporting other ecosystem services.  One of these ecosystem services is the biological control of pests, which will have effects in both switchgrass fields and neighboring areas.  For example, as a perennial crop, switchgrass will likely provide habitat for a variety of herbivores and their natural enemies.  To investigate the role of switchgrass cultivar and cropping system on insect communities and biocontrol services, a network of plots of switchgrass, alone and in combination with other grasses and forbs, was established across Southern Michigan.  The insect community of each plot was monitored June-August via sweep net samples. Sentinel prey (Helicoverpa zea eggs) were used to measure the biological control service at corresponding times.  Levels of biocontrol increased over the sampling season and different cultivars showed varied trends.  There were also differences in insect community composition in different systems.  Overall, the choice of cultivar and cropping system will influence insect communities and their provision of ecosystem services in agricultural landscapes.