FARGO, N.D.-A third year of major label changes for dicamba herbicide is unprecedented and there may still be more changes in 2020, university specialists say.
Jason Davis, a University of Arkansas pesticide application specialist, spoke Nov. 27 in the opening day of the 2018 Northern Ag Expo at the Fargodome. The event is sponsored by the North Dakota Agricultural Association, which represents seed, chemical and fertilizer industries. Dicamba was one of many topics on the first day of the expo.
Davis said scientists hope farmers get a better grasp on dicamba and keep it on target, but the rules continue to change as new scientific information arises..
Dicamba is a key ingredient in herbicides sprayed on soybeans and other crop varieties that are genetically-modified to tolerate it. The chemical is valued as an important tool in killing pigweeds and other weeds that have become tolerant to other herbicides including glyphosate, which most farmers know as Roundup, brand.
Non-dicamba-tolerant soybean varieties are highly sensitive and can suffer damages that can cut yields, although that can be affected by timing factors. Arkansas had 1,312 complaints for dicamba in 2017. That compared to an annual level of 100 to 150 for all pesticides and three annual complaints for dicamba prior to its first illegal use on soybeans in 2015 and 2016.
Arkansas dicamba complaints in 2018 declined 85 percent, Davis said, "We may not be quite out of the woods yet," he said.
Arkansas officials are working to extend application further into the season to benefit growers trying to use the tool. A draft proposal would institute two separate cut-off dates, which he thinks would be "a great challenge" to enforce.
"If these regulations go through unscathed, we might have regulations in mid-March," Davis said, noting that some of his training events would start in coming weeks.
Andrew Thostenson, a North Dakota State University Extension Service pesticide application specialist, said the federal label is more complex and limited in 2019. Those changes are:
• Mandatory requirements for training again, and an annual requirement.
• Elimination of the "direct supervision" rule, allowing farmers to oversee employees who are non-certified applicators. "You are either a certified applicator, a commercial or private or nothing else." In North Dakota, this should be less of a problem than some states because most of our commercial applicators are already are certified. "We may see an influx of 500 to 600 private applicators," he said.
• Records on application must be completed within 72 hours of application, rather than the 14-day period required last year.
• Application can be only from one hour after sunrise until two hours before sunset, according to the federal label. It was sunrise to sunset last year. This is to avoid temperature inversions.
• Dicamba can be applied 45 days after the planting date, or after when the plants first start to bloom, whichever is first.
• Applicators must observe a 24-hour rain-free interval whenever there is sufficient rainfall for runoff to be likely.
• There is a 57-foot minimum "omnidirectional buffer" if endangered species are in the area. Applicators must go to a website and indicate the location of intended spraying to determine proximity to endangered species. There already is a 110-foot buffer for downwind applications on susceptible species. The issue isn't likely to be a big issue in North Dakota.
• New cautionary language regarding tank mixes and pH (acidity) levels. A reduction of the pH of the spray solution can increase volatility.
Thostenson said the North Dakota Agricultural Weather Network has played a key role in making federal rule changes, especially regarding temperature inversions, which allow the chemical to drift like a cloud for miles.
He said he was surprised when NDAWN data from Grafton, N.D., showed there was only one day in the month of June 2018 when there was no temperature inversion. Inversions showed a difference of up to 9.3 degrees, between the 3-foot and 10-foot heights.
North Dakota Agriculture Commissioner Doug Goehring has the authority to impose further restrictions, Thostenson said. Details may come out in mid-December.
Thostenson called the 2018 adjustment on rules of applying a herbicide is unprecedented.
"I've been in this business 30-plus years. I have never seen anything like this in my entire lifetime," he said. "Every time I think I've seen everything, dicamba proves me wrong. Three labels in three years is astonishing to me."
Thostenson said a fourth label change could be possible again in 2020. He said the dicamba experience is making Environmental Protection Agency take more time in approving and labeling other products. He said that secondary impact is "hard to measure" but "I know that is, in fact, true."