Amid growing questions of nematodes' effect on corn yields in Ohio, a recent sampling in the 2011 Ohio Corn Performance Test locations found no visible evidence of nematode injury, an Ohio State University Extension specialist says.

Several seed companies submitted hybrid entries in the performance test that included nematicide seed treatments, said Peter Thomison, an OSU Extension agronomist. Soil samples were collected to assess whether nematodes may be present at test sites. Two bulk samples of 20 cores each were taken from each test site, all of which have a history of some form of conservation tillage, he said.

"Nine of the sites followed soybeans, one followed corn," Thomison said. "There was no visible evidence of nematode injury, such as uneven growth or stunted plants, in sampled plots."

The purpose of the test is to evaluate corn hybrids for grain yield and other important agronomic characteristics. Results of the test can assist farmers in selecting hybrids best suited to their farming operations and production environments.

The nematode analysis was done at Michigan State University's Diagnostic Services laboratory and was funded by Pioneer Hi-Bred, a DuPont company, he said.

"The lab results provided populations and a risk index for root-lesion, dagger, lance, stunt, pin and spiral nematodes," Thomison said. "Nematode populations were generally low to non-existent, with spiral nematodes being the most common nematode present in any quantities.

"With the exception of one sample from the Beloit location in Mahoning County, the risk index for the different nematode populations was 'none detected' to 'low.'"

At Beloit, one sample contained 56 dagger nematodes, indicating the potential for a moderate risk of damage, he said. The other Beloit sample indicated that nematodes were low to non-existent.

The testing was done as nematodes are receiving more attention as a potential yield-limiting factor in corn.

While it is unclear if Ohio corn growers will have a problem with nematodes, farmers, growers and researchers are taking a closer look at the issue to see if the tiny organisms negatively impact corn yields and if seed treatment nematicides are needed, according to Terry Niblack, an Ohio State University plant pathologist.

Nematodes are microscopic worm-like soil organisms that, depending on the species, can either benefit or harm the growth and development of corn. Their effects on corn roots are garnering more attention as the harmful species are being discovered in more cornfields throughout the Midwest, according to Niblack, a nematologist and chair of Ohio State's Department of Plant Pathology.

Plant-parasitic nematodes can be a problem for corn yields because they feed on corn roots and reduce root growth. Their root feeding reduces the plants' ability to uptake nutrients and water, and can also encourage bacterial and fungal pathogens to enter the plant.