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Wisconsin dodges dicamba bullet with a wait-and-see approach
dicamba damage
SOY BEAN PLANTS dis-playing the classic cupped leaves sign of damage from the herbicide dicam-ba.

WISCONSIN - Consensus in the agriculture community is that the state of Wisconsin dodged a bullet with problems associated with the herbicide dicamba in 2017.

“In 2017, so far, we’ve only had one complaint lodged from a farmer about damage to a so bean crop,” said Mark McCluskey, a DATCP  supervisor with the Environmental Program, Agrichemical Management Bureau. “I suspect the reason for this is that we didn’t see a lot of acres in the state treated with the herbicide this year.”

Ted Bay, retiring Grant County UW-Extension Agriculture Agent, confirmed that there had been one complaint made in 2017, originating in Grant County.

“There are rumors out there that there may have been more than one instance of dicamba damage,” Bay said. “I think that there is a reticence to file complaints because it can become a problem with neighborliness.”

Vance Haugen, Crawford County UW-Extension Agriculture Agent, reported that he has not heard of a single complaint in the county, on or off the record.

“The product can be quite touchy to use,” Haugen said. “At a recent training for pesticide applicators in Sparta, the instructors leading the training emphasized that while Dicamba can be another tool in the farmer’s toolbox, there can be problems with it, and farmers need to be very careful.”

Haugen thinks that area farmers tend to be a fairly conservative lot, who are more likely to wait and watch to see what happens when someone else uses the product. This, he believes, is part of the reason the county has not yet seen a lot of use of dicamba.

Haugen believes that a lot of the problems with herbicide resistant weeds come from excessive use of just one chemical versus taking a more diversified approach to chemical weed control.

“We have only had one official incident with a Roundup resistant weed in the county,” Haugen said. “The weed was water hemp, and we sent it off to a lab to be tested and it was confirmed as Roundup resistant.”

Haugen said that while water hemp is more common on bottomlands, because the seeds are moved around in harvest equipment, it is starting to pop up in ridge top fields as well.

Al Bark, owner of Ridgetop Ag in Mt. Sterling, confirms that he did not see much demand for spraying Dicamba in the 2017 growing season.

“We did no Dicamba spraying, and only sold Dicamba-ready seed to one customer,” Bark said. “I haven’t heard of any others spraying it either.”

Bark believes that with the increasing problems in the area with water hemp, palmer amaranth and giant ragweed, it is likely that more dicamba-ready seeds will be planted, and sprayed with the herbicide.

“For us, as applicators, Dicamba is a little bit scary to use, because of all the liabilities and restrictions,” Bark said. “It’s tough to get excited about using it.”

Bark emphasized that for professional applicators, one of the biggest barriers to using the product is the need to make sure that his equipment is thoroughly cleaned out when moving between jobs.

Swede Knutson, a corn and bean farmer in rural Ferryville, has also gone through the ‘private applicator training,” for herbicide and pesticide application.

“Really I think that the lack of use and potential resulting complaints in the state relate to the availability of the Dicamba-ready seed in our area,” Knutson said. “A lot of the varieties of soybeans that have been developed to be Dicamba-ready are for the longer growing seasons more typical to our south, where they have also seen more of the Roundup resistant weeds.”

Problems to the south

In the 2017 growing season, in such states as Arkansas, Missouri and Illinois, there was a surge of complaints about damage to soybean crops in fields adjacent to those planted in Dicamba-ready seeds and sprayed with the herbicide.

Literally hundreds of Midwest farmers have filed complaints with their state agriculture departments, and the total number of damaged acres may exceed 850,000 acres in Arkansas, and 300,000 acres in both Illinois and Missouri.

University of Missouri weed specialist and assistant professor Kevin Bradley worked to investigate the scope of the problems seen in Missouri. He found more than 1,400 dicamba-related complaints that had been filed with state regulators.

“I don’t know that we’ve ever in our agricultural history seen one active ingredient do so much damage,” Bradley said.

Dicamba damage

The problem with Dicamba, even though it works very well on the Dicamba-ready crops developed to tolerate it, is that it doesn’t always stay where it’s supposed to stay.

In hot weather, dicamba “volatizes,” turning into a gas that can drift for miles. Soybeans that haven’t been engineered to tolerate dicamba are extremely sensitive to it.

Tensions have run high over the allegations of damage in some areas. In October 2016, one farmer on the Missouri-Arkansas border allegedly shot and killed another farmer over the issue of dicamba drift.

More recently complaints have emerged that the misuse of dicamba may be responsible for damage to oak trees in Iowa, Illinois and Tennessee. The herbicide allegedly causes the leaves of the tree to “cup” and die.

Government response

In response to the large volume of complaints, both the states of Arkansas and Missouri temporarily banned use of the herbicide in mid-July of 2017. Missouri even went so far as to temporarily ban the sale of it, but then went on to develop new, stricter guidelines for its use and lifted the ban.

Most recently, an EPA ruling has specified that dicamba products will be ‘restricted-use’ pesticides, and will have additional restrictions. The herbicides will come with new label restrictions in 2018, such as record-keeping requirements, and certain additional spray drift mitigation measures.

These label changes will apply to Monsanto's XtendiMax herbicide, BASF's Engenia herbicide and DuPont Pioneer's FeXapan.

State pesticide regulators and agencies will be required to train all applicators before they can use the dicamba herbicides.

Applications are limited to sunrise to sunset, effectively banning nighttime spraying, when temperature inversions are most likely to occur. Applications are also limited to wind speeds of 3 to 10 mph.