Control weeds the old-fashioned way

You’ve got an opportunity to raise non-GMO soybeans and/or corn for a premium. There’s just one problem. How will you control weeds without glyphosate for Roundup Ready or Ignite for LibertyLink crops?

Crops consultants say it can still be done. Here’s how.

• Corn. “Use full rates of soil-applied grass herbicides or premixes compared to a reduced rate for GMO corn,” says Jeff Nagel, a certified crop adviser and agronomist for Ceres Solutions, based in Lafayette.

“Follow with a broad-spectrum post-emergence broadleaf herbicide. There are many good soil-applied grass herbicides, but fewer options for postemergence grass products. However, there are several good post broadleaf herbicides.”

Key Points

Return to the basics: Read labels and don’t skimp on rates.

A good residual grass-herbicide is key for weed control in non-GMO corn.

Spray while weeds are smaller than you’re accustomed to spraying.


Part of the secret in conventional corn, since there aren’t many good post options for grass control, is to start with a clean field, says Ryan McAllister, also a CCA. He’s with Beck’s Hybrids, Parker City. He suggests using burndown treatments to guarantee a clean start.

One issue that could be stickier in corn than beans is making sure you don’t have any volunteer GMO-crops growing with your non-GMO crop. Start as free of those as possible, says Danny Greene, a CCA, Greene Consulting Inc., Franklin. Even a small amount of volunteer GMO grain could cause a load to be rejected and the non-GMO premium denied.

Also, do your homework, and know that every herbicide you might consider for non-GMO crops won’t necessarily control the same weed spectrum as GMO herbicide options do. The application window may also be narrower in a non-glyphosate crop, Greene warns. He advises that you should be ready to scout and identify weed escapes.

• Soybeans. “Use a broad-spectrum soil-applied herbicide that reduces weed pressure for the post herbicide that will follow,” Nagel says. He advises against attempting a total post program with non-GMO soybeans. Part of the reason is the need to catch weeds small.

“Be sure to apply post on 2- to 4-inch tall weeds,” he stresses. A 2-inch weed isn’t very tall.

“Acceptable control can be obtained with timely applications, but if weeds get too large, it will be difficult to control them with conventional herbicides.”

Planning ahead is the key, Greene says, especially in non-GMO soybean fields. Read herbicide labels and note rotation restrictions to your next crop. If you haven’t grown non-GMO crops for a while, you may be out of the habit of reading labels and noting possible plant-back restrictions.

“A full rate of residual herbicide up front will increase the likelihood weeds will be manageable come post-application time,” McAllister says.

Adjuvants also become key in conventional systems. Again, it’s crucial to read the label and add what the manufacturer recommends to the tankmix.

Grasses will be relatively easy to control post in soybeans. Shutting down broadleaves can be a challenge if you let them get ahead of you. In a way, it’s the reverse of corn, where grass control options postemergence are limited.

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Sound the alarm: This young stand of soybeans is in trouble if you can’t use glyphosate. Broadleaf weeds are harder to bring down post in non-GMO soybeans.

This article published in the February, 2011 edition of INDIANA PRAIRIE FARMER.

All rights reserved. Copyright Farm Progress Cos. 2011.