Managing volunteer corn in soybeans will prove challenging for many growers in Eastern Canada in 2019.
The need to control volunteer corn is nothing new, but a troublesome 2018 harvest across Ontario and Quebec will make it tougher this year, says Steve Johns, agronomic sales representative with Syngenta Canada. Growers in many parts of Ontario battled an epidemic of Gibberella ear rot in corn resulting in unprecedented DON levels. To help manage the problem, combine settings were adjusted at harvest to help blow out diseased kernels. In some cases, fields were simply combined with the kernels being blown onto the ground.
In Quebec, Syngenta’s agronomic sales representative Eric Boulerice explains that growers wrestled with harvesting a very dry crop in poor late-season weather conditions that produced a lot of dropped cobs and kernel loss before the crop entered the combine. Like Ontario, Boulerice says many soybean fields will have much higher corn kernel populations that will germinate and produce volunteer corn management headaches in 2019.
Don’t put IP premiums in danger
It’s vitally important that growers control these volunteers in IP soybean crops, says Boulerice. “If there are too many kernels in the sample, you could lose the premium and opportunities in the export market.” He adds that volunteer corn will also create pain when combining Roundup® Ready soybeans and even greater problems for seed production as the presence of corn kernels in seed lots is frowned upon by seed companies.
“If you’re growing IP soybeans, controlling volunteer corn should be top of mind,” says Johns. But it should be a concern for all growers when they see the corn plants emerging in their soybean crop. Johns notes that research from South Dakota State University shows that volunteer corn density of 5,000 plants/acre can reduce soybean yields by 20% — that’s a 12 bu/ac yield loss in 60 bu/ac soybeans. Yield damage can be even more extensive in parts of a field where high numbers of dropped ears produce clumps of volunteer corn.
Volunteer corn is a weedy competitor
“A lot of growers really don’t see volunteer corn as a weed in their soybean crops,” says Johns. “In fact, it’s one of the most competitive weeds going.” Generally, he believes that growers spray volunteer corn too late. They tend to feel that more corn plants will emerge and wait for an opportunity to kill them all. “But’s it’s that first flush that will do the most yield damage,” he says.
Johns recommends that the best approach for growers is to apply solid pre-emerge herbicide programs and then target that first flush of volunteer corn at the 1st and 2nd trifoliate stage of soybean development (V1 – V2). “That’s when soybeans are most vulnerable to yield loss and that’s when we should be controlling volunteer corn,” Johns notes. Whether it be Roundup Ready 2 Xtend® or IP soybeans, growers do have herbicide control options including glyphosate, as well as Venture® L and Assure™. “Venture L is considered one of the most active products on volunteer corn and low rates will help tidy up volunteers pretty economically,” he says.
Corn rootworm resistance management
Controlling volunteer corn is also a good resistance management strategy, especially when it comes to corn rootworm. Johns points out that volunteer corn does not express the same level of Bt toxin for corn rootworm control as hybrid seed corn. That means volunteer corn can provide a bridge for rootworm to survive a soybean crop and pose resistance concerns for the following corn crop.
Boulerice says the final point growers need to consider is pre-harvest management, particularity in IP soybeans. Many times, growers feel they can clean up volunteer corn plants at harvest with a pre-harvest herbicide application. A typical pre-harvest burndown would be a low rate of glyphosate with Eragon® (saflufenacil). Growers need to remember that those volunteer corn are typically glyphosate-tolerant and Eragon offers no control of the maturing plants. That means these volunteers can go through the combine and be another source of contamination and potentially impact premiums.
“When it comes to volunteer corn, you can’t be complacent. It’s a weed and it will steal yield,” cautions Johns.
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Always read and follow label directions. Venture® L and the Syngenta logo are trademarks of a Syngenta Group Company. Other trademarks are the property of their respective owners. Genuity® Roundup Ready 2 Yield® crops contain genes that confer tolerance to glyphosate, the active ingredient in Roundup® brand agricultural herbicides. Roundup Ready 2 Xtend® soybeans contain genes that confer tolerance to glyphosate, an active ingredient in Roundup® brand agricultural herbicides, and dicamba, the active ingredient in XtendiMax™ herbicide with VaporGrip™ Technology. Agricultural herbicides containing glyphosate will kill crops that are not tolerant to glyphosate, and those containing dicamba will kill crops that are not tolerant to dicamba. Genuity®, Genuity and Design®, Roundup Ready 2 Xtend®, Roundup Ready 2 Yield®, Roundup®, VaporGrip™ and XtendiMax™ are trademarks of Monsanto Technology LLC, Monsanto Canada, Inc. licensee. © 2018 Monsanto Canada Inc. VaporGrip® is a registered trademark of, and used under license from, Monsanto Technology LLC. © 2019 Syngenta.