The western corn rootworm beetle, a pest that costs growers more than $1 billion annually in the U.S., can also survive on the perennial grass Miscanthus x giganteus, a potential biofuels crop that would likely be grown alongside corn, researchers report.
Rootworm beetle larvae can survive to adulthood on Miscanthus rhizomes, and adult beetles will lay their eggs at the base of Miscanthus plants grown near cornfields, the researchers found. Their study, in the Public Library of Science journal PLoS ONE, is the first to identify Miscanthus as a host of the corn rootworm.
The research team, from the University of Illinois Natural History Survey, tested several rootworm beetle populations on Miscanthus, adding rootworm eggs to potted Miscanthus and corn plants in a greenhouse setting. Rootworms from all populations survived to adulthood on the Miscanthus plants, including a strain that is behaviorally resistant to crop rotation. (Rather than remaining true to cornfields, rotation-resistant rootworms also will lay their eggs in soybean fields and other rotated crops, allowing the larvae to feed on corn planted in those fields the following spring.)
"The rotation-resistant rootworm is the population that is most familiar and troublesome to farmers in Illinois," notes Joseph Spencer, an insect behaviorist at the State Natural History Survey and co-author on the study with former Survey scientist Sathyamurthy Raghu.
"This form is spreading across the Corn Belt, putting a greater area of U.S. corn production at risk each year. The worst rootworm was happy on Miscanthus," Spencer adds.
Although the researchers found about 70% fewer adult rootworm beetles on the Miscanthus plants than on the corn plants grown in the greenhouse, the fact that rootworms could survive at all on this perennial grass was a revelation.
The implications for corn growers are not yet known, but these findings brought it home to us that much more study is needed, Spencer adds. "Before we put something out in the environment that could result in pest problems increasing on corn, we need to more fully appreciate the ecology and potential interactions in the environment," he concludes.