ARS | Publication request: Potential biomass reductions to Miscanthus × giganteus by stem-boring caterpillars

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 6, 2012
Publication Date: August 1, 2012
Citation: Prasifka, J.R., Bradshaw, J.D., Gray, M.E. 2012. Potential biomass reductions to Miscanthus × giganteus by stem-boring caterpillars. Environmental Entomology. 41(4):865-871.

Interpretive Summary: Injury from stem-boring caterpillars has been observed on the perennial grass ‘giant Miscanthus’ in both its native and introduced ranges. Because some species causing stem injury in the United States have not been identified, potential biomass reductions to Miscanthus were evaluated using southwestern corn borer (SWCB), an insect pest of several related crops including corn and sorghum. Results indicate SWCB is capable of survival on Miscanthus whorl and stem tissue from in the laboratory, and adults can develop from larvae placed onto Miscanthus plants under field conditions. Relative to uninfested tillers, Miscanthus with stem injury yielded 12–30% less dry mass in four infestations over two years. As in some other crops, damage from SWCB decreased as tillers increased in size or age. On plants infested in the field, greater total length of tunneling by SWCB produced greater losses of dry mass. While SWCB survival was not high, results suggest biomass production by Miscanthus could be limited by other caterpillars that attack related crops, including lesser cornstalk borer, sugarcane borer, or Mexican rice borer. For perennial grasses grown exclusively for biomass (like Miscanthus), strategies such as tillage or insecticide use may be uneconomical or impractical for stem-borer management, suggesting long-term investment in breeding for resistance may be needed.

Technical Abstract: Injury from stem-boring caterpillars has been observed on the perennial grass Miscanthus × giganteus Greef and Deuter ex Hodkinson and Renvoize in both its native and introduced ranges. Because some species causing stem injury in the United States have not been identified, potential biomass reductions to M. × giganteus were evaluated using southwestern corn borer, Diatraea grandiosella Dyar (Pyralidae), an insect pest of several related crops within the Andropogoneae. Results indicate D. grandiosella is capable of survival on whorl and stem tissue from hatch to 21 d in the laboratory, and field infestations with third-instars support adult development, as exuvia were found during dissection of injured tillers. Relative to uninfested controls, M. × giganteus tillers with stem injury yielded 12–30% less dry mass in four infestations over 2009–2010. As in some other D. grandiosella hosts, data indicate decreased susceptibility to stem-boring as tillers increase in size or age. Regressions of residuals for injured M. × giganteus tillers onto the cumulative length of tunnels per tiller also showed significant negative slopes (i.e., decreasing tiller mass with increasing tunnel length). While D. grandiosella survival appeared low in both laboratory and field trials, results indicate that M. × giganteus productivity could become limited by other stem-boring caterpillars known to attack Andropogoneae (e.g., Elasmopalpus lignosellus [Zeller][Pyralidae], Diatraea saccharalis [Fabricius] [Pyralidae], Eorema loftini [Dyar][Crambidae]). For perennial grasses grown exclusively for biomass, certain management strategies for stem-borers or other pests may be uneconomical or impractical, suggesting long-term investment in breeding for host plant resistance may be needed.