Volunteer Corn in Soybeans Harbors Secret Pest Problem

Volunteer corn is more than just another problem weed that escaped farmers’ herbicide programs in soybeans this season. While that’s problem enough, volunteer corn   can harbor a CRW population.

Agronomists are concerned those eggs are overwintering in fields across the Midwest now and will hatch to feast on corn planted to those same fields in 2023.

“It’s a situation where farmers won’t get the benefit they normally would from a corn-soybean rotation that would typically help break the pest cycle,” explains Brent Tharp, technical product manager for Wyffels Hybrids, Geneseo, Ill.

Tharp wants to alert farmers now to the potential for increased CRW pressure next spring. He believes the problem created by volunteer corn this season was set up by one of two factors or some combination of both. 

“Either there was lodging in the cornfield last fall (2021) and the combine didn’t get that corn harvested, or there was a problem with the chemistry the farmer used in his soybean field this season that didn’t control the volunteers,” Tharp says. “Either way, I’ve seen a lot of soybeans infested with volunteer corn this year.”

Scout Fields As You Combine
As farmers harvest soybeans this fall, Tharp encourages them to check fields for volunteer corn escapes and note their location—especially if CRW was a problem in those fields in 2021. 

Then, take CRW traits into consideration as you evaluate and select hybrids for planting next spring; or, you might want to give some consideration to using a soil-applied insecticide at planting with a non-CRW traited hybrid.  

Tharp also encourages you to monitor CRW populations next year by using sticky traps once adult beetles appear.

“The rootworm beetles are attracted to the yellow color on the traps,” he says. “The beetles fly into the trap and get stuck in the glue—there’s no pheromone used on the trap.” 

The population of beetles you capture in a field provides some indication of how significant a CRW issue you might encounter during the season, Tharp notes.

“If you’re not seeing many beetles, you probably don’t have much to worry about. But in areas where populations are above the threshold, next years corn crop may be at risk and you’ll want to consider your management options,” he says.

First-Year Corn Isn’t Always Safe
Tharp adds that certain segments of the CRW population have adapted around the corn-soybean rotation in the Midwest by an “extended diapause” (northern CRW) or the “soybean variant” (western CRW). Both variants can cause infestations in first-year corn and challenge farmers’ pest management plans. 

Wyffels offers free sticky traps to corn growers and also offers a corn rootworm monitoring program you can sign up for at its website wyffels.com, under the Agronomy tab.

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