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The volunteer corn you don't want can lead to rootworm problems in years to come

Volunteer corn is more prevalent in the 2022 growing season and can cause some yield losses, but Bruce Potter, an integrated pest management specialist at the University of Minnesota Southwest Research and Outreach Center at Lamberton, Minnesota, said the bigger issues are the insects and diseases that the corn can bring. Of particular concern is the corn rootworm.

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Volunteer corn dots a field of rye in northwest Minnesota in August 2022.
Jeff Beach / Agweek
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The stray corn plants dotting soybean and other fields is a problem this year and could be a bigger problem a year and even two years down the road.

Yes, the volunteer corn can cause some yield losses, but Bruce Potter, an integrated pest management specialist with University of Minnesota Extension, said the bigger issues are the insects and diseases that the corn can bring. Of particular concern is the corn rootworm.

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A corn plant that volunteered in a soybean field in the Red River Valley.
Jeff Beach / Agweek

“Having them lay eggs in volunteer corn makes it really messy,” Potter said of the rootworms.

If a farmer had planted soybeans or some other crop to manage rootworms or other problems, before going back to corn, the volunteer corn is a weed that throws a wrench in those rotation plans.

“So basically, you lose your rotation for some of the corn diseases,” Potter said.

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The western corn rootworm and northern corn rootworm can both be found in the upper Midwest. But Potter said the northern corn rootworm eggs have the ability to remain viable even over multiple winters, extending the potential for problems.

“Some of those eggs hatch the following year but a pretty significant portion are not going to hatch for two years out, sometimes even a little bit longer than that,” Potter said. “They just delay their egg hatch.”

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Bruce Potter, an integrated pest management specialist at the University of Minnesota Southwest Research and Outreach Center at Lamberton, Minnesota.
Mikkel Pates / Agweek

Potter works from the University of Minnesota Southwest Research and Outreach Center at Lamberton. He is seeing more volunteer corn this year in his part of the state, mostly in soybean fields but has been prominent in fields farther north into the Red River Valley, in sugarbeets and small grains, too.

“The good news is if you're far enough north, your rootworm populations tend to be a little bit lower,” Potter said. “So as you move south, it's more of a problem with continuous corn and westerns (rootworms). And as you move further north, the northern corn rootworms can tend to predominate. If you get far enough north, populations are down.

“But I've started to hear more reports of rootworms further north, too.”

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There are a few different factors contributing to the volunteer corn problem, such as corn bred to be herbicide resistant, but weather is a big factor.

“Well, one of the big reasons for large amounts of volunteer corn this year is we had a big wind event that went through southern Minnesota last summer and caused a lot of lodged corn,” Potter said. “Some of that didn't get picked up as well as it could have been, so there was a lot of grain on the ground and that germinated this year.”

Looking ahead to the next growing season, Potter said there are ways to keep corn in the rotation.

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Volunteer corn grows along the edges of a Red River Valley soybean field in September 2022.
Jeff Beach / Agweek

“So I think you're going to want to either use a good rootworm insecticide, an at-plant insecticide, and probably going to want to put a rootworm traited hybrid in there,” Potter said. “One of the things I think we've seen happen over time is that, you know, that volunteer corn and allowing rootworms to persist the following year, probably helped with some of the development of resistance.”

Potter said tillage would likely only delay the emergence of volunteer corn, because corn can germinate from as deep as 3 inches into the soil.

Potter said localized problems have been around for awhile, but this year it is more widespread.

“So it's gotten a little more difficult to kill it, but anytime we've had some adverse weather, we've seen some issues with volunteer corn in the fields,” Potter said.

Reach Jeff Beach at jbeach@agweek.com or call 701-451-5651 (work) or 859-420-1177.
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