Arkansas Plant Board to consider changes to dicamba regulations

The Arkansas State Plant Board will hold a special meeting Wednesday (Jan. 3) in Little Rock to discuss potential regulation changes for the use of the herbicide dicamba during the 2018 growing season.

ASPB had proposed to ban the controversial weed killer for the season, but the Arkansas Legislative Council’s Administrative Rules and Regulations Subcommittee decided Dec. 12 to hold the rule change to allow ASPB to possibly modify it before a final decision is rendered.

The Subcommittee asked ASPB to consider three separate criteria in any revision of the rule. ASPB was asked to consider scientific-based evidence; a dividing line to create north and south use zones across the Delta; ambient temperature and humidity applicable to temperature inversion during night hours.

The Subcommittee is slated to meet Jan. 16 to consider any changes to the rule.

Changes might include a later ban date in May or June, creating zones within in the state where it can be used later in the season, temperature considerations, and others.

The regulation, if left unchanged and passed, would ban dicamba from April 16 through Oct. 31. ASPB voted Nov. 8 to ban the herbicide. The regulations include exemptions for the use of dicamba in pastures, rangeland, turf, ornamental, direct injection for forestry, and home use. At least 29,000 written comments were received in advance of that hearing and 37 people testified.

ASPB made the decision to ban dicamba after it received about 1,000 damage complaints, primarily in Northeast Arkansas, starting in May potentially caused from dicamba drift. The decision was controversial, but the board decided the risks were too significant in imposing the ban and steeper penalties for misuse. Dr. Mark Cochran, vice president-agriculture for the University of Arkansas System, said the decision was based on the best evidence available when it was made by ASPB in November.

Dicamba has been banned in several states. Dicamba has been used as an herbicide for more than 50 years to manage 200 broad leaf weeds. It is a Weed Science Society of America Group 4 synthetic auxin – a plant hormone that causes plants to exhibit uncontrolled growth, according to the University of Arkansas. It is more volatile in warmer climates.

ASPB decided earlier this year to allow one formulation, Engenia dicamba, to be used in the state to fight pigweed, an aggressive weed that has plagued farmers in recent years. About 35% of the state’s 3.5 million soybean acres were planted with genetically-altered dicamba tolerant seeds. About 75% (300,000 acres) of the state’s cotton crop was planted with dicamba resistant seeds.

Scientists theorized dicamba was drifting into adjacent crop fields, gardens, and other places. Misapplications, weather conditions, or some other unknown factors may have caused the alleged drift. Tests proved the new formulations were less volatile than older ones, but there was still volatility, and it could last up to 36 hours after it was sprayed. Dicamba can attach to dust particles, meaning it can travel much further from target sites than previously thought.

Some additives enhanced the volatility. Ammonium sulfate and glufosinate increase the damage capabilities of dicamba. Researchers found damage could spread up to 220 feet away from an application site, nearly double the buffer distance the Environmental Protection Agency requires between dicamba and non-dicamba fields. Tests showed that if the wind blew in one direction for several hours, drift could cause damage on adjacent fields and then if the wind changed hours later, the same amount of damage would be caused there.