Evaluation of switchgrass for resistance to potential aphid pests

Switchgrass, Panicum virgatum L., is a perennial grass native to the North American prairie and has recently been identified as a practical biomass feedstock for energy production. However, the viability of switchgrass as a feedstock will be dependent, at least in part, on effective pest management strategies. To date, little is known about the potential insect pests of switchgrass populations being developed for bioenergy production; although, research on related warm-season grasses indicates that insect pests will emerge. Thus, it is important to identify potential insect pests of switchgrass and to describe the plant-insect interactions at multiple ecological levels. In this study, we identified two potential pests of switchgrass, Sipha flava (Forbes) (yellow sugarcane aphid) and Schizaphis graminum (Rondani) (greenbug), and set out to better understand the interactions between host plants and piercing-sucking insects. Four switchgrass populations (Kanlow, Summer, K x S, and S x K) were evaluated for resistance to these aphids, with significant differences being observed in damage ratings among the four populations of switchgrass.  Further, Summer consistently demonstrated the highest damage ratings, while Kanlow exhibited the lowest damage ratings. In addition to these screens, two more aphids are being evaluated as potential pests to switchgrass, Rhopalosiphum padi (L.) (bird cherry-oat aphid) and Diuraphis noxia (Mordvilko) (Russian wheat aphid). Preliminary results for these screens will also be presented.