Ohio insect carrying new corn virus

COLUMBUS – The black-faced leafhopper, an insect found in Ohio, has been identified as the vector of an emerging corn virus.

Ohio State University and USDA researchers have learned that the insect, which transmits the maize chlorotic dwarf virus, also transmits a corn virus discovered last year. The virus is labeled “Georgia unknown” since it has been found only 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,” Redinbaugh said.

Impact unknown. It’s not known how much impact the black-faced leafhopper has in transmitting the virus in Ohio cornfields. The virus is “persistently” transmitted by the insect, meaning once an insect acquires the virus, it can infect plants throughout its life.

In contrast, maize chlorotic dwarf virus is transmitted “semi-persistently,” meaning 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,” Redinbaugh said.

“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,” Redinbaugh said. “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 20 percent of Ohio farmers grow Bt corn.

Breeding for resistance. Researchers are taking steps to ensure the virus doesn’t become a major problem. Since the most economical and environmentally friendly approach to controlling virus diseases is incorporating 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 unknown.”