| Switchgrass is a perennial, C4 grass that has emerged as a model bioenergy crop for a large portion of the US. Because of the potential for switchgrass to occupy many acres, understanding how cultivar and planted stand diversity choices could impact insects and ecosystem services is key. To investigate how cultivars differed the preference of herbivores, fall armyworm was chosen to represent how a generalist, chewing herbivore. Two life stages were used to measure establishment, consumption levels, and life history traits on different cultivars of switchgrass. These experiments revealed that the lowland ecotype supported lower levels of feeding and tended to slow development. The second experiment investigated how herbivores, natural enemies, and biological control were impacted by different switchgrass cultivars and planted stand diversities. Switchgrass was established both as different cultivar monocultures and in mixtures with grasses and forbs. Sweep samples were used to collect arthropods and egg cards were used as sentinel prey to measure predation levels. While there were differences between sampling years, generally upland ecotypes supported a greater abundance of herbivores, natural enemies, and ultimately higher levels of biological control. The effect of planted stand diversity was more mixed. Diverse plots hosted more herbivores in both years, but more variable natural enemy numbers and no differences in biological control. Clearly, choices about which switchgrass cultivar and seeding diversity to establish can impact herbivores, arthropod communities, and potentially ecosystem services. |
