Mixing it up: Dicamba adds to crop-protection complexities

Illinois farmers share what they're seeing and hearing throughout the state while U of I weed expert tries to sort out fact from fiction.

A soybean plant that Jeremy Wolf, a farmer from Champaign County, believes has been damaged by dicamba applied to kill weeds in neighboring fields. “We just want to learn as much as we can about this while we have this opportunity,” Wolf said. (Photo by Jeremy Wolf)
A soybean plant that Jeremy Wolf, a farmer from Champaign County, believes has been damaged by dicamba applied to kill weeds in neighboring fields. “We just want to learn as much as we can about this while we have this opportunity,” Wolf said. (Photo by Jeremy Wolf).
By Chris Anderson, Jeff Brown, Mike Orso

As instances of dicamba exposure in soybeans have increased recently, University of Illinois weed scientist Aaron Hager believes the number of affected acres will continue to increase.

However, Hager noted there appears to be some confusion about symptoms of dicamba exposure compared to leaf symptoms caused by nondicamba factors. In the latest crop and pest Bulletin, Hager said dicamba exposure involves several collective symptoms. They include:

- Extreme cupping of trifoliolate leaves, especially upper trifoliolates.

- Veins of affected leaves tend to assume a parallel orientation instead of the usual net venation pattern.

- Tips of cupped leaves with parallel veins are often brown or cream-colored.

- Plants are stunted and may sometimes remain stunted the remainder of the season.

- Depending on time and dose of exposure, pod development can be adversely affected.

“When dicamba is applied in a state that grows soybeans, the occurrence of off-target symptoms is not a question of ‘if,’ but rather ‘scale.’ Some suggest the solution is to plant all soybean acres to dicamba-resistant varieties. That might solve issues associated with soybeans, but would likely increase the incidents of damage to other dicot species across the Illinois landscape,” Hager noted.

Jeremy Wolf, a Homer farmer, said he has experienced damage to his soybean fields from neighboring ones where crop protection products that included dicamba had been applied.

“When you pour your heart and all of your effort and time into producing a crop and then you walk in and you find damage, it’s upsetting. It makes your heart drop,” said Wolf, of Champaign County. “It’s the situation we’re in, and we just want to learn as much as we can about this while we have this opportunity.”

Related: Don’t let dicamba take over your weed-management plan. Click here.

John Haase, a Mount Carmel farmer, said he planted Roundup Ready 2 Xtend soybeans on fields isolated from neighboring nonresistant soybeans and homeowners.

“We want to keep the technology, but people plant different varieties of beans and other sensitive crops. We’ve got to keep those people in mind, too,” Haase told the RFD Radio Network®.

The Wabash County farmer bought recommended spray nozzles last winter and paid close attention to wind speed and direction before spraying.

In an interview with FarmWeekNow.com Wednesday, Hager continued to stress the need for careful stewardship related to new crop-protection products that contain dicamba.

“There’s not a thing wrong with the technology, but people have to understand, this is dicamba,” said Hager. “We’re not seeing anything that we haven’t seen before. Why did we ever think we were going to spray more acres of dicamba in Illinois and not have issues with it? That goes against 50 years of experience. Are we going to continue to have issues with it in the future? Certainly.”

To read more from Hager on “The Dicamba Dilemma in Illinois: Facts and Speculations,” go to this link.

Some parts of Illinois may still be in the #spray17 window. For more information, go to ilfb.org/steward.

Content for this story was provided by FarmWeekNow.com.

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Don't let dicamba take over your weed management, reminds Hager

By Jeff Brown

Midway through the first year of dicamba-tolerant soybeans and accompanying crop-protection technology both being commercially available, Illinois farmers have likely learned plenty about the technology that will be useful moving forward.

University of Illinois weed scientist Aaron Hager hopes those aren’t the only weed-management lessons from the past that farmers take with them into the future.

Dicamba is just one of many components of an integrated weed-management plan. And Hager says farmers need to continue using all available tools to not only eliminate resistant weeds but also maximize the effectiveness of dicamba herbicides.

If you’re using dicamba this season, here are three tips to keep in mind:

1. Don’t ignore other weed-management practices.

Stay integrated in your approach to weed management. Hager shakes his head when he hears farmers talk about how much they need to keep dicamba technology because it’s the last available tool.

“Number one, you’re actually overlooking several obvious tools – there’s a Liberty Link system, there are other non-chemical systems that still work on resistant weeds,” he said. 

“And number two, if your only solution is that you’re going to spray all these acres with dicamba, then I question if we’ve learned anything from past experience. If that’s our solution to this, if all we’re going to do is rotate and spray dicamba, that’s actually going to limit the effective lifespan of this technology.”

2. Don’t focus so much on dicamba that you ignore other potential weed hot spots.

Proper weed management requires constant scouting and treatment to make sure weeds don’t produce seed. For example, farmers need to keep their eye on their CRP land for resistant weeds.

“If you’ve got CRP areas, go scout those again this year and make sure you’re not growing Palmer amaranth there,” he said. “That’s sort of lost the attention because of some of these other issues, but it’s every bit as important that we try to keep Palmer amaranth at bay rather than let it spread across the state.”

3. Don’t ignore the buffers.

The label on dicamba herbicide products prohibit their use on buffer zones around field edges. But that doesn’t mean you have to allow weeds to grow there.

“If you ignore the buffers, you just created a weed nursery in your field,” Hager said. “The only limitation is you cannot spray the dicamba products (in the buffer zones); that does not limit you from doing anything else in that area,” such as using other residual herbicides or removing weeds by hand.

Some parts of Illinois may still be in the #spray17 window. For more information, go to ilfb.org/steward.