Spraying Gets Specific

Individual States Grapple With Dicamba Restrictions

The long list of spray requirements to use dicamba herbicides continues to grow as some states fine tune labels for the coming spray season. (DTN photo by Pamela Smith)

DECATUR, Illinois (DTN) -- The drama over dicamba herbicide use continued this week as some states wrestled with requiring spray regulations over and beyond new federal labels.

Evidence of continued turmoil came on Dec. 12, as an Arkansas Legislative Council subcommittee kicked a proposed ban on in-crop use of the herbicide from April 16 through Oct. 31 back to the Arkansas State Plant Board (ASPB). The committee approved a motion by Sen. Bill Sample (R-Hot Springs) to hold the rule for final consideration and recommended the state board revise it, using the following: scientific-based evidence; a dividing line to create north and south zones in the state; and ambient temperature and humidity applicable to temperature inversion during night-time hours.

Earlier Monsanto, the developer of the genetic trait that allows soybeans and cotton to withstand dicamba applications, had asked Pulaski County Circuit Judge Chris Piazza for preliminary and permanent injunctions against the Plant Board's spray ban. In the lawsuit, Monsanto called the action arbitrary and "not based on science." A group of farmers has also initiated legal action against the ASPB regarding what would be the nation's toughest line on dicamba herbicide.

The ASPB received nearly 1,000 dicamba-related complaints this year of damage to soybeans, cotton and other sensitive crops and landscape trees and plants. The proposal to limit the application period originated from a specially appointed dicamba task force and was approved on Nov. 8 during a public hearing that attracted hundreds of farmers. The ASPB has met more than 50 times on the issue of dicamba over the past five years, board members told DTN.

However, according to news reports, the subcommittee's vote isn't final. It is subject to review Friday by the Legislative Council, a group of lawmakers that conducts the General Assembly's business when it is not in session. ASPB members have indicated to DTN some tweaking of the dates of the ban might be possible without prolonged public comment periods.

While Arkansas has been in the dicamba spotlight, other states also are taking action. Last week, weed scientists gathering in St. Louis for the North Central Weed Science Society meeting stressed the need for farmers and retail applicators to monitor specific state requirements that might go over and above new federal restrictions. New federal rules were put into place in October on Engenia, FeXapan and XtendiMax herbicides.

Most of the state-by-state changes are being made, they stated, because the federal EPA labels do not address herbicide volatility. The herbicide industry has hotly contested volatility as an explanation for at least some of the more than 2,700 official complaints of injury reported in 2017 across the cotton and soybean belts.


On Tuesday, the Minnesota Department of Agriculture (MDA) announced new restrictions on the use of the herbicide dicamba in Minnesota for the 2018 growing season. The decision follows the MDA's ongoing investigation and an informal survey last summer into reports of crop damage from alleged dicamba off-target movement.

In a news release, Minnesota Agriculture Commissioner Dave Frederickson said he thoroughly reviewed the new EPA label restrictions, the MDA's survey results, peer reviewed literature, and sought extensive input from the Minnesota Soybean Growers Association Drift Task Force, University of Minnesota Extension weed scientists, and the pesticide manufacturers on the underlying causes of damage.

Based on the review, the Commissioner set forth these additional protocols for dicamba use for the 2018 growing season:

Cutoff date: Do not apply after June 20. Setting an application cutoff date of June 20 is expected to help reduce the potential for volatility (movement). The majority of Minnesota soybeans are still in the vegetative growth stage by June 20 and research has shown that plants in the vegetative stage are less affected than those in the reproductive stage.

Cutoff temperature: Do not apply if the air temperature of the field, at the time of application, is more than 85 degrees Fahrenheit or if the National Weather Service's forecasted high temperature for the nearest available location for the day exceeds 85 degrees Fahrenheit. Research has shown that dicamba volatilization injury increased with an increase in temperatures.

"Dicamba is an important tool for soybean growers to manage weeds and I believe these additional restrictions will minimize the off-target movement," Frederickson said. He added that the state will be closely monitoring the herbicide's performance with these restrictions in 2018."


Indiana, North Dakota, Missouri, and Tennessee are some of the other states that have increased or are in the process of fine-tuning dicamba application restrictions.

In Missouri, for example, certified applicators must complete an online Dicamba Notice of Application form daily prior to each application. Cut-off dates for applications in that state also differ by county.

In North Dakota, no applications of the three new-generation dicamba herbicides may be made after June 30 or after the first bloom (R1 growth phase), whichever comes first. No applications may be made if air temperature of the field at the time of application is over 85 degrees Fahrenheit or if the forecasted National Weather Service high temperature for the day exceeds 85 degrees Fahrenheit.

In writing the regulations, it was noted that North Dakota has a unique climate that is different than other soybean-producing states. The application season typically has low humidity. The dry and less humid environment can significantly increase product evaporation and potential off-target movement. Applications of the product may only be made from one hour after sunrise to one hour before sunset.

Applicators must maintain a speed of 12 miles per hour or less when applying products. Applications must be made with a minimum of 15 gallons of spray solution per acre. No applications may be made using nozzles that have an 80-degree or less spray pattern.


Anyone buying, applying or even working under the supervision of a certified applicator must complete a dicamba-specific training course, said Kevin Johnson, Illinois Fertilizer and Chemical Association (IFCA) director of government and industry relations. Applicators that cross state lines will need to understand and abide by the specific rules in that state, Johnson added.

While farmers hiring custom applicators are not technically required to attend application class, Johnson strongly encourages the training for anyone planning to plant Xtend varieties and potentially use the herbicides labeled for those varieties. "The labels for these products are complex and there may be cases where a commercial applicator cannot spray. The education will help explain those situations," Johnson said.

For more information on state dicamba regulations go to:

North Dakota: https://www.nd.gov/…

Minnesota: http://www.mda.state.mn.us/…

Missouri: http://agriculture.mo.gov/…

Tennessee: https://www.tn.gov/…

Pamela Smith can be reached at Pamela.smith@dtn.com

Follow her on Twitter @PamSmithDTN