Proceedings of the South Dakota Academy of Science, Vol. 91 (2012) 245 THE IMPACT OF BLASTOBASIS REPARTELLA (DIETZ) (LEPIDOPTERA: COLEOPHORIDAE) ON SWITCHGRASS Veronica Calles Torrez*, Paul J. Johnson, and Arvid Boe Insect Biodiversity Laboratory Department of Plant Science South Dakota State University Brookings, SD 57007 *Corresponding author email: [email protected] ABSTRACT Switchgrass (Panicum virgatum L.) is a potential biomass production crop and is important as a model for biofuel synthesis. A potential pest, the Switchgrass moth (Blastobasis repartella (Dietz)) larva feeds in the rhizome, proaxis, and basal internodes of the tillers, causing premature tiller death which directly affects biomass accumulation. The focus of this study was to determine among cultivars the frequency of tiller infestation, the differences in biomass production, and biomass loss. Two experimental areas established in 2004 and 2008 in Brookings County, South Dakota, were used in 2011. Sampling plots were arranged in a Randomized Complete Block design with six replications and six cultivars. A frame of 1 ft2 was placed in the plot and all tillers within were cut at ground level. Tillers were categorized as infested and uninfested tillers, counted, dried at room temperature, weight, and recorded. Analysis of variance for differences was used and the least significant difference to compare means. Statistical output showed no significant difference among cultivars in frequency of infestation in both areas. There was a significant difference in production and loss of biomass in the newer area as well as for biomass production in the older area, but not for biomass loss. Infestation rate was statistically identical in all of the cultivars. Sub- sequently, we found that early instar larvae feed on new tiller buds on subterra- nean rhizomes from late summer through winter, indicating a potentially greater impact on biomass production than that measured by the tiller assessment. .