Date of this Version
Bioenerg. Res. (2012) 5:189–196; DOI 10.1007/s12155-011-9120-z
Insect damage to prairie cordgrass, Spartina pectinata Link., is conspicuously high in Illinois, where attempts to collect native seed show the majority of spikelets damaged with small holes. Dissection of spikes during summer reveals minute caterpillars boring though glumes and feeding on florets inside. In 2009–2010, panicles of prairie cordgrass from across its native range were used to estimate the percentage of insect-related damage and losses to seed production. Collections of caterpillars from panicles and stems were used to identify one floret-feeding species, estimate its distribution in the central USA, and assess its feeding patterns within spikes. Insect feeding damaged 38% of spikelets across eight states, though injury differed significantly between states. Regression of developed prairie cordgrass seeds onto insect damage suggests a 1:1 loss ratio (i.e., 50% damaged spikelets reduces seed production by 50%). Collections of caterpillars from six midwestern states suggest that larvae of a tortricid moth, Aethes spartinana (Barnes and McDunnough), are responsible for most insect damage to cordgrass spikelets. Larvae of A. spartinana generally feed on a series of consecutive spikelets, with high infestations (>50% insect damage) showing damage concentrated in the middle of spikes. Because larvae are concealed by moving into adjacent spikelets and later tunneling into cordgrass stems, they may be difficult to control using insecticides. While direct effects of the caterpillar on biomass yields for prairie cordgrass are not known, for states like Illinois (where damage to spikelets often exceeds 70%), breeding and seed production efforts may be severely limited without efforts to manage A. spartinana.