As soybean producers roll through the fields harvesting, some may find their beans fared a little better this season. There have been fewer reports of herbicide damage, according to South Dakota State University and the state’s department of agriculture.
Through the growing season, there have been nearly 60 fewer cases of damage from off-target dicamba filed with the South Dakota Department of Agriculture compared to last season. This year, the department had just over 110 cases while last season, they fielded 170 official cases.
Dicamba tolerant soybeans were first approved for planting in 2017, but there were problems with the herbicide drifting on to fields of conventional beans and causing damage. A record number of complaints were filed all across the Midwest, which sparked many states to revise dicamba spraying guidelines for the 2018 season.
Coordinators at the SDSU Extension office believe the newest spraying rules held up well for the season as producers got a hang of when and how dicamba drifts.
Paul O. Johnson, an extension weed science coordinator, believes the successes of 2018 are attributed to two main factors: adopting self-imposed cutoff dates for spraying and using the right nozzle heads during application.
SDSU recommended a cut-off date of June 21 but due to an overwhelming about of moisture in southeastern South Dakota, many applicators missed that date. Dicamba has a federally mandated cutoff after R1, or the first reproductive phase.
Although self-imposed cutoff dates are rarely strictly followed, Johnson said that commercial applicators followed their own guidelines and realized that the potential for damage wasn’t worth the risk.
While using the right nozzle and following the guidelines for spraying helped, Johnson said the biggest adjustment made this year was actually in regards to spraying or not spraying during weather inversions.
“They weren’t sure why they had a problem,” Johnson said. “This year, people were a lot more cognizant of things like inversions.”
A weather or temperature inversion is a reversal of the normal behavior of air temperature in the atmosphere. When spraying a herbicide like dicamba during these inversions, pockets of the chemical tend to stick closer to the earth’s surface instead of dissipate into the upper atmosphere. Applicators being aware of these inversions and avoiding spraying during these times was a huge key to the decline in complaints this year, Johnson said.
While Johnson said it wasn’t entirely the producers’ fault last year for misuse of the chemical, he said that sometimes guidelines and rules are hard to understand until you experience it firsthand.
“You can preach and preach, but sometimes it really doesn’t sink in,” he said.
After this season, Johnson said regulators may once again debate the possibility of adding a hard cutoff date to dicamba spraying, but he doesn’t believe it was likely to get one.
“When you put a hard and fast rule in, it’ll sometimes cause problems,” Johnson said.
The problems include the possibility of weather effecting spraying for long enough that applying must be delayed, but the biggest concern would be applicators spraying a few days before the deadline no matter the weather conditions simply to meet that part of the regulation.
The biggest change for next year will be in the form of a new soybean variety. Johnson said there are new soybean seeds coming out that will be tolerant to both dicamba and Liberty herbicides, allowing for producers to switch between the chemicals depending on the weather.
“With those new beans, the farmer will have options for spraying,” Johnson said. “That’ll be a real help to avoid problems in the future.”