Hear the report by KUAR's Daniel Breen.

Inside a squat, brick building set among roughly 800 acres of row crops, a mix of scientists, local growers and Arkansas Plant Board members prepare to get a look at an all-too-familiar problem.

They'll be touring the University of Arkansas System Division of Agriculture's Northeast Research and Extension Center in Keiser, near the banks of the Mississippi River. Plant Board Chair Greg Hay prepares the group for what they're about to see.

"Again I want to stress that we're here to look, listen and learn. It's one thing to see photographs of dicamba damage. It's another thing to see it first hand on a landscape scale,” Hay said.

Jason Norsworthy has warned this same group about the herbicide dicamba many times. It's used on fields of genetically modified cotton and soybeans, and has a tendency to cause damage to non-tolerant crops. Norsworthy, a weed scientist at the University of Arkansas, says that's cost the Division of Agriculture roughly 250 acres of experiments, worth about a $500,000.

"We're not going to see any research today in terms of research, my research. We're going to start off by looking at some breeding plots, but in terms of the research, all the research here is gone,” Norsworthy said.

The plant board first restricted dicamba's use in 2017, after it received thousands of complaints of damage. In February, after a group of farmers complained, the board voted to push the last legal date when dicamba can be sprayed to May 25 from the previous date of April 15.

When dicamba is mixed with other commonly-used herbicides like RoundUp, it’s more likely to vaporize in high temperatures. But the landscape of the Arkansas Delta poses a problem called "atmospheric loading."

Much like the way mountains trap pollutants in cities like Los Angeles, dicamba vapor, when sprayed in high concentrations in a short period of time, is trapped in the Delta by Crowley’s Ridge. Temperature inversions, which increase the concentration of pollutants, also happen frequently in the Delta.

This, Norsworthy says, causes widespread damage on farms, whereas damage from drift would be contained to a smaller area.

"This is what you're going to see over the entire station, right there. The entire station's going to look like this. Some areas are going to be worse, some areas may be a little better if the beans were larger. Very uniform symptoms," Norsworthy said.

But soybean farmers in Arkansas haven't had the easiest season, and some swear by dicamba as the most effective way to get rid of an invasive plant called Palmer amaranth, or pigweed.

Most of the soybean leaves the group inspects show the trademark "cupping" indicative of dicamba damage. Even fields planted within the past 20 days have begun to show signs of damage, which Norsworthy says is proof that neighboring growers violated the May 25 cutoff date.

"We have had symptoms on these beans since May the 25th. There has been no cease in spraying around here because if they had stopped spraying, you would eventually had some good growth in the top of that bean. We've had constant exposure since May the 25th."

Tom Burnham planted non-dicamba tolerant LibertyLink soybeans this year at his farm near Blytheville, since heavy rains delayed planting past the spraying cutoff date. That proved to be a mistake, he says, since most of his crop is showing damage.

"It’s the company's fault. There's no doubt about it, they’ve got a faulty product. I mean, they’ve got the Ford Mustang that blows up [when you] run into the back of it, man," Burnham said.

But aside from blaming BASF and Bayer CropScience, the largest manufacturers of dicamba, Burnham has another theory as to why damage is so bad this year.

"I've been told from reliable sources that, as far as enforcement of this, it's being winked at all the way from the top of this state's government. 'Hey, don’t fine them, don’t enforce it,'" Burnham said.

"I'm going up higher than the state Plant Board, I’ll tell you that right now."

Farmers can be fined as much as $25,000 for illegal spraying, but so far this year, out of the 114 alleged dicamba complaints on file with the board, the 9 cases that have been closed have all found no violation. But Norsworthy says it's nearly impossible to find who's guilty when the atmosphere is full of dicamba.

"Yeah, they're spraying all around. 'Is it coming from there? Is it coming from there? Is it coming from there?' Yeah, it's coming from all of them. There is no way anyone will ever go out here and tell me the field this stuff came out of."

Norsworthy says the Keiser research station isn't the only one to get hit with dicamba; he says his counterparts in Iowa and Illinois have reported similar damage patterns. He says the damage at Keiser has caused years' worth of experiments to be lost, with some needing to be moved to Fayetteville, which has a much cooler climate than the Delta.

Speaking to NPR, representatives for Bayer and BASF said they were aware of damage at research stations (in BASF's case, at their own facility in Marion), but also said dicamba doesn't cause problems if used correctly.

After the tour, Crittenden County grower Franklin Fogleman, who led the group of farmers that got the spraying cutoff date pushed back, asks Chair Greg Hay what the Plant Board will do next.

"The one thing that we could probably all agree on… is that a lack of an action about a plan for 2020 is one thing that could be bad for every producer," Fogleman said.

Hay says he doesn't expect any change in regulations to come out of the board's next meeting in September, but Norsworthy says, despite the numerous tweaks to the rules surrounding dicamba, growers and researchers are still stuck with the same problems.

"It's the Plant Board's decision as to what they do, how they move forward, again I don't think anything's going to happen anytime soon," Norsworthy said.

"[2017] has come and gone, [2018] has come and gone, [2019] has come and gone, and we're still where we were at the start of this."