Corn’s rise could increase nematodes

Are farmers setting themselves up for a serious increase of an old pest by growing corn like crazy in Arkansas? Well, yes and no, according to Terry Kirkpatrick, Arkansas Extension plant pathologist.

Corn, never a big crop in the South, has become one of the hottest crops to grow because of skyrocketing prices spurred by the boom in ethanol production.

Everyone, it seems, loves corn, including root knot nematode, a tiny organism that feeds on the roots of plants.

“As we move corn acreage into former cotton acreage, we’ll see an increase in root knot nematodes,” said Kirkpatrick, director of the Nematode Diagnostic Laboratory at the Southwest Research and Extension Center at Hope.

“All the corn hybrids we use today are good hosts for root knot nematodes,” Kirkpatrick said. “Corn roots are huge so there are lots of infection sites for nematodes to use. So the reproduction of root knot nematodes on corn is substantial.”

This surplus of root knot nematodes is carried over to the next year’s crop whether corn, soybeans or cotton.

One upside of raising corn is that it’s not a host for two other kinds of nematodes: reniform and soybean cyst. Raising corn where these nematodes are a problem will cause a decline in their numbers, according to Kirkpatrick.

“For farmers in Monroe County and several southeast counties where reniform nematode numbers have been climbing over the last several years, they’ll see that problem going the other way by growing corn,” he said.

Kirkpatrick said he has been asked several times, “What nematode problems are we going to get into if we grow a substantial acreage year after year?”

There’s no research in Arkansas on the effect of nematodes on corn that Kirkpatrick is aware of because corn hasn’t been an important crop here for many years. But research in Georgia and the Carolinas leads Kirkpatrick to believe repeated corn production will increase lesion nematodes.

However, some serious types of nematode pests that are a problem in Georgia and the Carolinas probably won’t be a serious problem in Arkansas because of the differences in soil types, the nematode expert says.

Kirkpatrick advises farmers to learn what kind of nematode they’re dealing with in a field.

“You have to know what type of nematode you have and what (populations) are before you know what crops to use and rotate and what nematicides to use,” he said.

He advised farmers to wait until the end of the growing season, and take soil samples in their corn fields. Kirkpatrick’s nematode lab can test the samples and let farmers know if they’ve increased their root knot nematode problem and decide on a crop to grow next year and how to manage that crop.

“If you’ve increased your root knot nematode problem, you need to be aware so that you can plan to manage them appropriately in the next crop,” he said. “There are nematicides, and, in some cases, resistant varieties that can be used to manage nematodes in cotton and soybeans.”

Although there is no research on the effects of subsoiling on nematodes in Arkansas, research in some states indicates that breaking up the hardpan can have an impact on controlling nematodes or at least improve plant performance in the face of nematodes.

For more information on crop pests or for information about soil sampling, contact your county Extension agent.

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