Dicamba Drama Continues

January 20, 2018

Written By Adam Buckallew

Drift concerns remain as dicamba-resistant seed sales are set to double

The 2017 soybean harvest is likely to set a new record for total production, but for many farmers, the year was marred by the finger-pointing, lawsuits and acrimony associated with off-target movement of dicamba herbicide.

The hotly debated weedkiller resulted in more than 2,700 formally submitted injury complaints to regulators, and an estimated 3.6 million acres of soybeans may have been damaged by drifting dicamba applications. But those figures don’t paint a full picture of the scope of the problem, according to Kevin Bradley, a weed scientist with the University of Missouri.

“For every reported case, there are probably ten more that go unreported,” Bradley says.

The proliferation of resistant weed species, several of which are now tolerant of multiple herbicidal modes of action, has left farmers searching for solutions to keep their fields free of these yield-robbing nuisance plants. When the Environmental Protection Agency (EPA) approved dicamba-resistant soybeans (marketed as Xtend) for use in 2016, farmers were excited to have another tool at their disposal in the war on weeds.

Unfortunately, it’s proven difficult to keep the volatile chemical from moving off-target. In addition to reports of damage to approximately 4 percent of the nation’s soybean acreage, greenhouse plants, gardens, orchards and even residential landscapes have suffered damage linked to dicamba.

The drift complaints not only have pitted neighbors against one another, but also threaten to strip farmers of a potentially valuable management tool. The current registration on dicamba for use in Xtend soybeans runs only through Nov. 9, 2018, and will automatically expire unless EPA officials determine “off-site incidents are not occurring at unacceptable frequencies or levels” before that date.

Preserving Weed Control Options

Carl Woodard, who raises row-crops in Grundy County, Mo., has yet to plant any Xtend soybeans himself, but he fully understands the challenges of resistant weeds and the need for tools to combat them. Missouri has 14 species of weeds that have developed resistance to herbicides, and waterhemp, which has been documented to resist six different herbicidal modes of action, is among the most vexing.

“Waterhemp and other resistant weeds have been on a lot of growers’ minds the last few years, and they are only getting tougher,” Woodard says. “There’s no doubt that’s driven farmers to look for new control options like over-the-top spraying of dicamba.”

Many of the soybean fields in Woodard’s area that had been planted with Roundup Ready soybeans in the past were switched to Xtend soybeans last season, and he expects to see more in 2018. But he says farmers on both sides of the dicamba debate cannot afford another season with so many drift complaints.

“It’s seems to be a tricky product to control, even when you are doing everything right and following the label,” Woodard says. “I like the technology and its effectiveness in controlling tough weeds, but that can’t come at the expense of your neighbors’ crops or garden. I hope the off-target movement issues get figured out, because it seems to be an effective tool for weed control. It’s not like there’s a bunch of new herbicides coming down the research pipeline.”

Drift Causes Division

The turmoil and uncertainty surrounding dicamba was the subject of the keynote address at the University of Missouri’s Crop Management Conference in December.

University of Missouri Extension’s Bradley says he’s heard from farmers on both sides of the issue, and he’s concerned with what the debate is doing to rural communities.

“There’s been so much divisiveness and animosity…I’ve never seen anything like this before and I was around for the introduction of Roundup Ready crops,” Bradley says. “It’s unprecedented in its scope. Some people have had their whole livelihood destroyed by this issue, and it’s become a black eye for agriculture.”

Bradley points to a lack of appreciation for the inherent sensitivity of soybean to extremely low concentrations of dicamba as one of the biggest reasons why so many farmers and herbicide applicators have run into issues.

“If soybeans are hit with even 0.005 percent of the labeled rate, it can cause injury,” Bradley notes.

The timeframe when dicamba drift occurs is also an important factor in determining potential yield loss in soybean. Bradley presented research which showed soybeans injured by dicamba after flowering begins are likely to experience yield loss, while beans hit during the vegetative growth stages are less likely to have their yield compromised. But Bradley took issue with farmers who tried to discount instances of drift by claiming they only caused cosmetic damage.

“Even if that were the case, when did it become okay to allow your sprayings to drift onto neighbors?” Bradley asked at the conference. “It’s never been that way before. We’re not allowed to chemically trespass on our neighbors.”

New Rules and Restrictions

Despite the challenges, sales of Xtend soybean seed are expected to double nationally, and Bradley expects that to be the case in Missouri as well. While the adoption of the trait technology broadens, new restrictions have been put in place in an effort to minimize the potential for drift damage.

EPA announced in October it had reached an agreement with Monsanto, BASF and DuPont on new requirements for in-season applications of Xtendimax, Egnenia and FeXapan, the herbicides formulated for use with Xtend seed. The products have been reclassified as “restricted use,” meaning only certified applicators with special training, and those under their supervision, can apply them. Farmers will also be required to maintain specific records regarding the use of the products, and applications will be limited to times when wind speeds are blowing at 10 miles per hour or less.

Several states have added their own restrictions for “over the top” applications. The Missouri Department of Agriculture has issued the following Missouri-specific restrictions for Xtendimax, Egnenia and FeXapan:

• Restricted Use Pesticide – For sale to and use ONLY by certified applicators. Non-certified applicators are prohibited from applying these products.
• Training – Prior to the purchase and/or use of these products, certified applicators must complete mandatory dicamba training provided by University of Missouri Extension. Training verification must be presented to the retail establishment, pesticide dealer or distributor.
• Notice of Application – Certified applicators must complete an online Dicamba Notice of Application form daily prior to each application. The form can be found at agriculture.mo.gov/dicamba/notice.
• Application Timing – The products cannot be applied before 7:30 a.m. or after 5:30 p.m.
• Cutoff Dates – Farmers in Dunklin, Pemiscot, New Madrid, Stoddard, Scott, Mississippi, Butler, Ripley, Bollinger and Cape Girardeau counties cannot use the products after June 1, 2018. All other counties must stop use by July 15, 2018.

In Arkansas, the situation for growers remains unclear. The Arkansas Plant Board had proposed a statewide ban on dicamba spaying from April 16 to Oct. 31, 2018. That recommendation was forwarded to the Arkansas Legislative Committee for review. However, in December, the legislative committee asked the plant board to consider revising its proposed rules using “scientific-based evidence, a dividing line to create north and south zones, and ambient temperature and humidity applicable to temperature inversion during night-time hours.” The plant board is expected to reconvene in January to review the issue.

While the new rules may help curtail physical drift and problems associated with temperature inversions, they fail to address the questions surrounding the volatility of dicamba.

“BASF and Monsanto have invested a lot of money to make these newly approved (dicamba) formulations less volatile,” Bradley says. “And they are less volatile. But as many have said, less volatile does not mean not volatile.”

Until the volatility issues have been solved, Bradley recommends farmers exercise caution.

“My recommendation for those growers who wish to plant the Xtend technology is to go back to using dicamba at a timeframe and in a manner when it has been used successfully in the past,” Bradley says. “Based on our history of dicamba use in corn in April and May, and even on our experiences this year using these approved dicamba products in pre-plant burndown applications prior to June, we have seen far fewer problems with off-target movement of dicamba in that timeframe than what we experienced in June, July and August.”