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Sample to spot corn nematodes

Are nematodes why some cornfields got off to a slow start? Did you notice yellow, stunted patches? Are you sure it was just wet soils? Or could nematodes be part of the reason?

The only way to know for sure is to send a soil sample, and preferably also a plant sample, to a nematology lab, notes Bryan Overstreet, Extension ag educator covering Jasper and Pulaski counties. With lots of sandy soils, those counties have long been plagued by soybean cyst nematode. Sandy soils are also home to needle nematodes, which feed on root surfaces.

Key Points

• Soil and plant samples, if available, are best way to confirm nematodes in corn.

• The last two weeks of June are the best time to sample for corn nematodes.

• Handle nematode soil samples carefully to assure accurate results.

“The best time to take samples for nematodes is mid-June until the first of July,” says Overstreet, an Indiana certified crops adviser. “This is when all species of nematode are active.”

Sending plant samples becomes helpful when you see visual symptoms. However, nematodes may cause damage without distinct symptoms. If there are aboveground symptoms, send both soil and plant samples from good and poor areas, he advises. Unlike with soil samples for nutrient analysis, it’s important to keep these soil samples cool.

If you don’t see symptoms, take soil samples in a random pattern, Overstreet advises. Let one sample represent 10 acres. Take cores 4 to 6 inches deep.

Where to send samples

Purdue operates a nematology lab. Find the forms to send with your samples at Then send the samples to: Nematology Laboratory, Department of Entomology, Purdue University, 901 W. State St., West Lafayette, IN 47907-2089.

Cost of each sample is $10, notes Betsy Bower, an agronomist for Ceres Solutions in western Indiana. Bower is also an Indiana CCA.

“Results of root feeding nematodes can be determined rather quickly,” Bower says. These are species that feed on root surfaces.

“However, to determine if nematodes are feeding within roots, the roots must be incubated for a few days,” she adds. This assay picks up different species.

Adds Steve Dlugosz, also a CCA, “The surest diagnosis for corn nematodes involves taking soil samples from the root zone.” The crops consultant works with Harvestland Co-op in east-central Indiana. Pay careful attention to sampling details, Dlugosz emphasizes. Nematode samples require careful handling in order to assure accurate results.


Bad hombre: Needle nematodes can wreak havoc on corn roots.

This article published in the June, 2010 edition of INDIANA PRAIRIE FARMER.

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