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Switchgrass, Panicum virgatum L., along with two other perennial warm-season grasses, big bluestem (Andropogon gerardii Vitman) and indiangrass, (Sorghastrum nutans L), compose a majority of the grasses found in North American tall grass prairies and have recently received attention as potential bioenergy feedstock. Limited research has been carried out on the relationship of arthropods on these three warm-season grasses in North America. Due to this limited research, the first objective of this research was to document the arthropods associated with switchgrass, big bluestem and indiangrass in Nebraska and Wisconsin over three sampling seasons. More than 10 arthropod orders and over 67 families were collected between the two locations with some of the most abundant families collected including: Carabidae, Chloropidae, Cicadellidae, Figitidae, and Thripidae.
Previous research has documented greenbugs (Schizaphis graminum Rondani) and yellow sugarcane aphids (Sipha flava Forbes) as potential pests of switchgrass, but limited information is available on the host suitability of big bluestem and indiangrass to these two aphid species. Therefore, the second objective of this research was to document aphid feeding preference among these three grass species through a series of choice studies and to characterize greenbug feeding behaviors using the electric penetration graph (EPG) technique. Choice studies identified differences in the preference of two aphid species in response to the three grasses with switchgrass being most preferred by Schizaphis graminum at 1, 2 and 4 h; whereas switchgrass was the least preferred by S. flava starting at 24 h after aphid introduction. Feeding behavior studies of S. graminum on switchgrass, big bluestem and indiangrass indicated that greenbugs took significantly more time before achieving the first sieve-element phase (salivation and ingestion of sieve element phloem sap) when feeding on indiangrass compared to both switchgrass and big bluestem, suggesting resistance factors in indiangrass are associated with phloem tissue. These studies are the first to examine the feeding preference of S. graminum and S. flava on big bluestem and indiangrass. This research provides important baseline information about the arthropod communities associated with the three warm-season grasses, and advances our understanding of the plant-insect interactions within this system.
Advisors: Tiffany Heng-Moss and Thomas J. Weissling