The Dicamba Dilemma

November 5, 2017

Written By Michelle Cummings

No easy answer to herbicide controversy

Uncertainty is swirling in the Midwest, where millions of acres of crops may have been damaged by a controversial herbicide. An estimated 3.1 million acres of soybeans have been affected by off-target movement of dicamba across the country, and that figure doesn’t include other crops.

More than 2,400 formal complaints have been filed citing plant injury caused by dicamba in 2017. Though the official reports are troubling, the true number of affected farmers is likely much higher since many attempt to settle issues among themselves rather than involve regulatory agencies.

Missouri and Arkansas saw enough dicamba-related complaints that state officials felt the need to issue temporary bans on the herbicide. The Missouri Department of Agriculture lifted its one-week ban in July after placing additional restrictions on how the herbicide could be used.

Arkansas may take further steps. A state task force recommended an April 15 cut-off date for spraying the weed killer in the 2018 crop year. The task force sent the recommendation to the Arkansas Plant Board and Arkansas Gov. Asa Hutchinson. They may forward it to lawmakers in Little Rock if changes to the state law are proposed.

Volatility Issues

For many soybean farmers, dicamba has become an important tool in their war against weeds. In 2016, the introduction of Monsanto’s Roundup Ready Xtend system with soybean and cotton traits tolerant to dicamba and glyphosate gave growers a means to combat resistant weeds. Consequently, the use of the herbicide has surged in the last two years.

Unfortunately, dicamba has frequently moved off-target, injuring plants in nearby fields, gardens and backyards and causing disputes among neighbors. A number of reasons could potentially account for why farmers experienced so much trouble with dicamba moving off-target this year, including: physical drift, spraying with the wrong type of nozzle, spraying during a temperature inversion and the herbicide’s volatile nature.

“The majority of fields I’ve been in are injured from one end to the other with no discernable difference in soybean symptomology,” said Kevin Bradley, the University of Missouri’s weed extension specialist. “This suggests problems with off-site movement through volatility.”

When agro-chemicals volatize, it means they turn from liquids to gasses, which can enable them to travel farther than intended. In the case of dicamba, Bradley said the weed killer is not simply hopping field borders, but rather “it appears to be moving miles.”

“The big debate is whether or not the stuff is volatilizing,” Robert Hartzler, an Iowa State University weed scientist, told the Des Moines Register.

“New formulations were supposed to have taken care of the volatility problem,” he said, “but all the research suggests that they’ve reduced the volatility, but not to a level that’s safe” after plants have emerged from the ground.

The chemical companies which sell dicamba herbicides for the over-the-top spraying of crops – BASF, DuPont and Monsanto – have mostly deflected blame to farmers and applicators, who they say have failed to follow product labels. However, some extension experts say even farmers who do everything right have had trouble keeping dicamba in their fields.

Larry Steckel, a weed management specialist with the University of Tennessee, said the label on dicamba herbicides may “look straight forward on paper,” but adhering to all the restrictions can be equated to a “Herculean task.”

“Talk about threading the needle — you can’t spray when it’s too windy, you can’t spray under 3 miles per hour, you got to keep the boom down — there are so many things,” Steckel said. “It looks good on paper, but when a farmer or applicator is trying to actually execute that over thousands of acres covering several counties, it’s almost impossible.”

Growing Concern

Bradley has dealt with dicamba problems the last two years. Most dicamba-related problems occurring in 2016 were concentrated in Missouri’s Bootheel region, but complaints have spread to more than 50 state counties in 2017.

“I get calls daily from those who say we have a major problem with off-target movement of dicamba, and something has to be done about it,” said Bradley. “Most of these calls are from soybean farmers who have had their crops drifted onto.”

Though Missouri’s dicamba problems have shown up in more locations this year, the Bootheel is still the epicenter for the most complaints and damaged acres. Bradley estimates of the approximately 875,000 acres of soybeans planted in the Bootheel, about 65 percent have the Xtend trait and were almost certainly sprayed with dicamba. The remaining 306,000 acres of soybeans would be susceptible to damage from off-target dicamba applications, and Bradley estimates 195,000 acres of the non-Xtend soybeans (or 64 percent) have been injured by the herbicide.

The high concentration of cropland sprayed with dicamba in the Bootheel is significantly greater than other parts of the state and has influenced many farmers’ seed-purchasing choices.

“When your neighbors are all using the same product, you have to adapt,” said Kris Robinson, a Bootheel farmer in Steele, Mo. “I was seeing damage from other farmers’ application of dicamba and was forced to switch to using Xtend soybeans.”

Robinson plans to continue planting Xtend soybeans in an effort to avoid damage from nearby fields. His decision to switch to the dicamba-resistant seed may work for his operation, but it is not viewed as a universal solution for other growers.

“Many farmers believe they should have the freedom to plant what they want,” Bradley said. “There’s a lot of harsh feelings with this issue. Many believe they shouldn’t have to disregard their current personal seed of choice and plant a new product out of fear.”

A Path Forward

Tensions concerning dicamba continue to rise among farmers, researchers and the companies which supply the dicamba herbicides. The U.S. Environmental Protection Agency (EPA) is reviewing the issue. The agency has yet to determine what steps it will take to mitigate problems associated with dicamba, however, it plans to implement additional rules for the herbicide’s use.

Though EPA has yet to publicly comment on how it will act, officials within the agency expressed concern to AgProfessional.

“We don’t consider this normal growing pains for a new technology,” said Dan Kenny, acting Registration Division deputy director for the EPA Office of Pesticide Programs. “We don’t feel it’s helpful to solve a problem for one grower and create a problem for another.”

EPA is aware farmers need to make decisions for 2018 soon.

“We are working as fast as we can to make meaningful changes for the 2018 growing season,” said Reuben Baris, acting branch chief of EPA’s Office of Pesticide Programs, Registration Division herbicide branch. “We are working with the registrants to make meaningful regulatory changes so growers are able to make the most informed decisions for the 2018 season.”

Iowa State University’s Hartzler participated in a July 28 teleconference with EPA officials and academic weed scientists from states experiencing issues with dicamba. He said EPA is working to gather information on the scope of the problem to chart a path forward.

“Both groups (academics and regulatory) acknowledged the need for new tools to help manage the herbicide-resistant weed problem, but recognize that the extent of off-target injury observed in 2017 (and in some states last year) is unacceptable,” Hartzler said. “Difficult decisions will need to be made on how dicamba is utilized in the future that will preserve the value of the tool while protecting sensitive plants in the landscape.”