Editor: Photos are available. Contact Candace Pollock or OARDC photographer Kenneth Chamberlain at (330) 263-3779 or firstname.lastname@example.org. WOOSTER, Ohio - The black-faced leafhopper, an insect found in Ohio, has been identified as the vector of an emerging corn virus.
Ohio State University and U.S. Department of Agriculture researchers have found that the insect, which transmits an existing virus called maize chlorotic dwarf virus, also transmits a corn virus that researchers discovered last year. The virus is currently labeled "Georgia unknown" since it has only been found in an isolated area of that state the past two years.
Peg Redinbaugh, a USDA plant molecular biologist, said researchers are hoping to name the virus "maize fine streak virus," based on the symptoms it incites. The virus causes fine chlorotic streaks that run along the veins of the plant leaf. "Because the virus also causes dwarfing, we would expect substantial yield reductions in infected plants," she said.
Redinbaugh said that it's still unknown how much impact the black-faced leafhopper will have in transmitting the virus in Ohio corn fields. The virus is "persistently" transmitted by the insect, which means that once an insect acquires the virus, it can infect plants throughout its life cycle. In contrast, maize chlorotic dwarf virus is transmitted "semi-persistently," meaning the insects can infect plants for only a few days.
"The insect is found in large enough numbers in Ohio that it can transmit other viruses, so there is potential for possible spread of the emerging virus," said Redinbaugh. "But on the other hand, we've never seen the virus before and it's only been found in fall planted Bt sweet corn in Georgia, so whether the insect will transmit the virus to field crops remains to be seen." Researchers speculate that Georgia farmers who planted Bt sweet corn did not spray to control for insects like the fall armyworm and the corn earworm. "Because the black-faced leafhoppers don't do much damage to corn, farmers don't spray to control them," said Redinbaugh. "But any spraying done on non-Bt corn would normally keep leafhoppers out of the fields." There are no fall plantings of field corn or sweet corn in Ohio. About twenty percent of Ohio farmers grow Bt corn.
Researchers are taking steps to make sure the virus doesn't become a major problem. Since the most economical and environmentally friendly approach to controlling virus diseases is to incorporate virus-resistance into the crop, they have begun to look for lines that show resistance to the virus. For example, Oh1VI, a recently released line with resistance to maize chlorotic dwarf virus, had very low rates of infection by "Georgia unknonw." Lines that are resistant to a related virus, maize mosaic virus, also showed a high level of resistance to the virus.
The virus is currently being cloned to help researchers better understand the relationship between it and its vector. "Once we begin to understand the interaction between the virus and the insect that transmits it, then we can develop highly targeted, environmentally sustainable approaches to controlling the insect or preventing the disease," said Redinbaugh. "The emergence of this virus in Georgia points out how complicated environmental issues really are. You may make huge advances in controlling for major pests, but then there are others that can emerge." Redinbaugh is part of a joint program between Ohio Agricultural Research and Development Center and USDA scientists dedicated to tracking the emergence of corn diseases worldwide. The group, based at OARDC's Wooster campus, is responsible for analyzing maize viruses from the United States and around the world.