Checking Up on Dicamba


June 23, 2017

Story provided by The University of Illinois.

Many soybean producers are turning to Dicamba to keep weeds at bay, but Todd Gleason with the University of Illinois Extension says it’s important to check your fields carefully after spraying.

Dicamba has been around for about half-a-century. It is a corn herbicide, but soybeans have been modified to tolerate it. This was done because so many weeds have modified themselves to resist being killed by Glyphosate, commonly known as Roundup.

“The primary problem,” says University of Illinois Extension weed scientist, Aaron Hager, “Is waterhemp. Dicamba, in the 50 years that we’ve used it, has never been excellent on any of the pigweed species. It can be good – it can be very good. But it is not excellent. It is not as consistent.”

This inconsistency makes the timing of Dicamba applications extremely important. “Without a doubt,” says Hager, “Most post-applied herbicides are going to do a better job of controlling a full suite of weeds in a field when the weeds are less than three to four inches in size.”

“Certainly, with something like Dicamba and waterhemp, our recommendation to farmers is to treat very, very small weeds, but to go back in about 10 to 14 days and to scout those treated fields. Look to see what the efficacy has been. Sometimes we can twist up these pigweed plants, but that doesn’t mean they will necessarily be completely controlled.”

“It is possible for the weeds to recover, flower, and produce seed. And that,” says Aaron Hager, “Is something to avoid.”

The Environmental Protection Agency approved the use of Monsanto’s XtendiMax herbicide for use on Roundup ready 2 Xtend soybeans late last year, but some growers are still having problems with drift. The Arkansas Plant Board will vote again today on an emergency ban of all in-crop Dicamba applications after more than 200 complaints of Dicamba damage.