Watch Out for Corn Nematodes

The pest is not new, but a growing problem.

Published on: Aug 27, 2007

Lurking across the Corn Belt is a native pest that may be seeing a return to prominence. Corn nematodes are on the rise across the heartland thanks to changes in cultural practices growers have made. Major crop protection companies are hard at work on solutions, which could be available as soon as 2008.

"This is going to be a huge issue," says Terry Niblack, professor of nematology, University of Illinois. "Farmers have not worried about corn nematodes for three or four decades, but production practices that used to suppress nematodes are no longer used."

Niblack notes that these nematodes are native prairie nematodes that parasitize grasses, while the soybean cyst nematode is actually a non-native invader that came with the exotic soybean when that crop's cultivation became popular. She points to three major changes that could contribute to the rise of the corn nematode in the next decade as a growing crop pest.

First, the use of no-till has grown. "No-till is good for a lot of things, but it is especially good for some types of plant parasites," Niblack notes.

Second, declining use of two key classes of crop insecticides is a challenge too. Both carbamates and organophosphates are used less, in part due to farmer worries over safety; and in part because new biotech and seed treatment products offer an alternative.

"While those pesticides weren't specifically labeled for nematode control, one of the side benefits of their use was a suppression of the nematode population," Niblack adds.

Current soil-applied insecticides and seed treatments use pyrethroids or nicotinoids, neither of which have action on nematodes. And Bt technology is targeted at other pests.

Finally, the rise of corn-on-corn rotations creates an environment where this pest can flourish and rebuild a once weaker population.

In essence, the problem is returning after being out of the limelight for decades. The good news, and one reason you may be hearing more about the pest, is that major chemical companies are working on a solution.

On display

During field days this summer, Bayer CropScience and Syngenta Crop Protection are talking about new seed treatment products that have action on corn nematodes. University testing is underway, but those results won't be ready until much later this year. "We will evaluate the products after harvest," Niblack says.

University of Nebraska Extension Plant Pathologist Tamra Jackson, is also doing field research with seed treatments to explore their impact on corn nematodes. "There's not much I can say about the products now, but after harvest there will be new information available."

This cornfield near Erie, Ill., was shot several years ago, but shows the potential power of corn nematodes to impact yields.

For now, Jackson has been working on surveying the problem in her state to determine its extent. With samples already submitted, the work begins on analyzing the soil and crop samples to characterize the problem. Jackson notes there are at least 12 genera of nematodes capable of feeding on corn, and eight are known to live in Nebraska.

Company support of research on corn nematodes has returned, thanks to the potential for these new products, and Jackson welcomes the support. For now she's turning to older publications for information to help farmers. "This is a pest that hasn't been a problem, but we're on the edge of changing times," she notes.

As you attend field days this summer, look for talk about corn nematodes and new treatment approaches, you're sure to hear something. These new compounds could be approved for market as early as 2008, which offer some limited availability that soon, but look for a lot more information in 2009. For example, Bayer CropScience has a biological compound today - numbered GB126 - that is undergoing testing in some university trials. If marketed, it would be delivered as a seed treatment.

Syngenta already markets Avicta for nematode control in cotton, and is doing extensive research in the seed treatment market. And there's potential in the corn market as farmers grow concerned about the pest. Stay tuned for more on this issue after harvest.