The use of a pre-emergence herbicide in weed control for corn production has received new emphasis in the past couple years for two main reasons—glyphosate-resistant weeds and the introduction of new herbicides that can actually provide one-pass season-long weed control.

“I think we need to focus more on not having weeds than what is going to kill the weeds. That is why I plan around a one-pass herbicide program,” said Philip Huffman, partner in Huffman Enterprises, Dayton, Ohio.

“There is a lot of university data out there that shows small weeds in emerging corn, or even somewhat larger corn, results in substantially more negative yield impact than what we realize,” he said. “For that reason, a reliable residual product that provides a clean start is extremely important.”

On the other side of the Corn Belt, Mike Jones, Bayer CropScience technical service consultant located in eastern Iowa, confirmed Huffman’s reasoning for putting a residual pre-emergence herbicide down. “I’ve read university reports of how once weeds and grasses are to the two- to four-inch height and competing with corn that has just emerged, a grower has already lost somewhere between seven to 10 percent of the potential yield. If corn is priced at $5 to $7 per bushel, that lost yield is a pretty significant amount of money. This makes a pre-emergence weed control program that keeps a field clean pretty economical.”

Huffman reinforced his opinion by explaining the problem with two-pass herbicide programs. “In the Roundup Ready world, some recommendations have been to put down a short-term residual to just hold back weeds until glyphosate can be sprayed to kill those that come up after planting. I believe fields need to be clean from day one all the way through to harvest, and farmers shouldn’t need to be concerned about having to make that second pass to kill emerged weeds.”

Additionally because of glyphosate weed resistance issues, Huffman prefers not applying glyposate every year in a field. “I prefer to see glyphosate used only every other year. Honestly, I like to see skipping a year with any mode of action used in a field,” said Huffman, who farms and operates the ag retail operation in southwest Ohio with his father, James.

As for how to achieve that clean field from planting to harvest, Huffman says growers need to look at the new pre-emergence herbicides that have been introduced. “There are a lot of older technologies that have their place, especially in a two-pass herbicide program, but not in one-pass programs,” he said. “Our experience is that the older pre-emergence herbicides will not perform in a one-pass program. Many growers don’t have experience with some of the new chemistries, and I don’t think they realize how much better the new ones are than the older ones.”

“We recommend and use Corvus plus atrazine, which gives us three modes of action against broadleaf weeds and grasses. Corvus is a product that we recommend because we appreciate its ability to keep fields clean early but also kick in to stop weeds that try to emerge following new rainfall.”

If there is a field where weeds happen to break through because of extreme weather, it’ll usually be spotty, and the most likely candidate for follow up to avoid using glyphosate is Laudis, contends Huffman.

Huffman reports farmers have had success using Corvus, even with challenging weather conditions this year. And Jones reports farmers in Iowa have had extremely good results with Corvus one pass, too.

“This year I think less than three percent of the Corvus acres treated at a full rate (5.6 fluid ounces per acre) plus one and a half pounds of atrazine received any post-emergence herbicide application,” Jones said.

For more information, contact Jones at