By Candace Krebs

After nearly 3,000 reports of dicamba injury involving an estimated 3.6 million acres in 25 states last year, the Environmental Protection Agency and major chemical manufactures instituted strict new requirements on application and training related to new dicamba tolerant crops.

The change isn’t expected to have much impact in Colorado, where so few soybeans are grown that they aren’t even included in National Ag Statistics Service acreage reports. Still, Colorado State University extension specialists want to make sure the word gets out.

“There’ve been no reports of dicamba injury in the state that I’m aware of,” said John Spring, CSU’s extension weed specialist based in the Holyoke office. “Our acreages are so small in comparison to the Midwest. Few people are growing soybeans out here, but we don’t want anyone to fall through the cracks.”

New formulations of dicamba herbicide for use on Roundup Ready Xtend soybeans and cotton are the only products that fall under the new guidelines. Dicamba is actually an old herbicide that has always been susceptible to vaporization and drift.

“Glyphosate doesn’t have that issue, but with dicamba it’s always been an issue,” said Ron Meyer, CSU area agronomist in Burlington. “That’s why we’ve never used it when we’ve had 100 degree weather, because it will gas off and move.”

Chemical companies Monsanto and BASF did introduce new formulations of the herbicide that were intended to be more stable and less drift-prone than previous versions. Older forms are not authorized for use with the new herbicide tolerant crops.

Even so, rates of dicamba drift injury were so high last summer in states like Arkansas that officials there temporarily banned it and eventually put strict limits on its use.

Last year Oklahoma reported 33 soybean complaints and 11 cotton complaints related to dicamba drift, affecting roughly 25,000 acres. In Kansas, the number of acres affected was closer to 100,000 acres and in Nebraska it was around 50,000 acres.

“Whether you’re a certified applicator or just driving the application equipment you have to be trained,” said Todd Baughman, a weed specialist with Oklahoma State University. “Even if you went through training last year, you’re still required to go through the approved training this year as well.”

The extension services in Nebraska, Kansas, and Oklahoma are all hosting multiple training workshops to satisfy the new requirements, while in Colorado, the State Department of Agriculture will handle any necessary training. All of the states have a reciprocal training agreement.

“Any training provided by the surrounding states meets federal requirements and will be good in Colorado,” Spring said.

A leading culprit behind drift that occurred in states like Arkansas, Tennessee, and Missouri last year is something called an “inversion,” where a layer of cool air is trapped close to the ground and doesn’t allow the chemical to disperse. It normally occurs in very still, moist weather conditions.

“We don’t see those very often here in Colorado,” said Spring, who is originally from Washington State and joined the CSU extension staff last July.

During the Commodity Classic last month, Monsanto introduced the “RRXtend Spray App,” a tool that helps applicators and growers plan their applications by predicting weather conditions and inversion risk for their fields.

The new requirements and heightened application concerns are a new thing for applicators and farmers to adjust to, Spring noted.

“They are really very restrictive and intensive compared to anything else that’s out there for other herbicides. It’s going to be quite a change for some people,” he said. “It’s an extra burden because it’s different than anything we’ve seen.”

As glyphosate resistant weeds drive the push toward development of more crops tolerant to other herbicide chemistries, management requirements will likely continue to intensify, Meyer added.

“2-4 D is also very volatile, especially in hot weather,” he said. “There are a couple of products out there like that.”

Farmers are looking for new products to help manage herbicide resistant weeds. Monsanto reported earlier this year that it expects U.S. farmers to plant 40 million acres of its dicamba-tolerant soybeans in 2018, double what was planted last year and equal to four of every 10 acres of projected soybean plantings.

“Glyphosate resistant kochia is the major one I hear about that is having a big impact here in Colorado,” Spring said. “Palmer amaranth and water hemp are not well established but there’s a lot of worry about where that will go, given the resistance and aggressive nature of those weeds in other parts of the country.”

“There are other modes of action that we can bring in. That’s an active area of research going on in Kansas, and I have a very small project looking at it too,” he added. “But it’s not going to be as cheap and easy as spraying glyphosate was.”

Farmers should prepare to see additional training requirements in the future as a result, Meyer said.

“As we get broader use of herbicides forced on us by resistant weeds, we will have to be better trained on the use of those products,” he said.

Farm chemicals in general require handling with care. The Golden Plains extension district recently presided over its third pesticide sweep, which allows farmers to bring in old pesticides for disposal in exchange for a flat fee of $7 a pound, no questions asked.

“We’ve collected 5,000 pounds of material so far, and our county commissioners love it, because that way it doesn’t end up in the local landfill,” Meyer said.