After wading into waist-high soybeans that on the surface appear healthy, Mark Baioni reaches deep into the plants to show their true condition.

"Here's the cupping," he said, holding some leaves that look puckered and withered.

Baioni, 60, who farms 2,500 acres near Marion, Arkansas, is among a group of East Arkansas farmers suing the makers of a herbicide that they say has drifted from the fields where it was sprayed and settled onto their crops, causing major damage.

In the class-action suit, the farmers say Monsanto Co., along with BASF Corp. and DuPont, placed greed ahead of responsibility in persuading growers to spray their fields with dicamba, a product known to be highly volatile and prone to drift.

Filed in U.S. District Court in St. Louis, the suit represents a new phase of a controversy that has roiled the rural Mid-South, spawning hundreds of farmer complaints, prompting emergency state restrictions and even precipitating a fatal shooting.

Dicamba, a weed-killer sold under a number of brand names, has been around since the 1940s, but this is the first year it's been fully legal to spray on cotton and soybeans that already have sprouted. The product is sold in conjunction with seeds that have been genetically modified to tolerate it, which allows farmers to spray the herbicide directly on their rows without damaging crops.

The product, however, has proved to be highly volatile for days after it's been sprayed. During temperature inversions, tiny droplets can rise and hang in the air, eventually to be blown onto other fields that weren't planted with the genetically modified seeds. Dicamba also can vaporize after being sprayed and then settle miles away.

So far this year, more than 600 farmers in Arkansas, as well as about 70 in Tennessee and more than 130 in Missouri, have lodged complaints with state agriculture officials claiming that dicamba used by other growers damaged their crops.

In response, Arkansas and Missouri have approved temporary bans on the sale and use of dicamba, while Tennessee restricted spraying to certain hours and ordered other changes.

The intensity of feelings over the herbicide became especially apparent last October, when a Monette, Arkansas, farmer was shot to death while arguing with the manager of another farming operation that he blamed for dicamba damage, authorities said.

In their suit, the six East Arkansas farming operations -- all but one of them from Crittenden County -- claim dicamba used by other growers caused damage that ranged from 220 to 3,400 acres of their crops. Most of the losses involved soybeans, but peanuts and even trees have been damaged, as well, the suit says.

Because crops haven't been harvested yet, the monetary losses haven't been tallied.

In their suit, the farmers say the manufacturers of the herbicide -- not the growers who used it -- are to blame. "This is not farmer against farmer," Baioni said.

Monsanto, in particular, rushed its dicamba-tolerant seeds to market even before the U.S. Environmental Protection Agency approved the herbicide's use on crops that already had sprouted, the suit says. As a result, farmers were pressured to use older, more drift-prone versions of dicamba.

EPA last November finally approved so-called "over-the-top" spraying with a formulation of dicamba designed to be less volatile. But the approval came after Monsanto witheld information about the herbicide and refused to allow independent testing on its tendency to drift, the suit says.

The farmers also claim that in order to limit damage from the widespread drifting of dicamba, more and more growers will have to use the more expensive genetically modified seeds, along with dicamba, as defensive measures. That ensures a "repeating cycle of increased sales and profits" for the defendants, the suit says.

The suit accuses Monsanto and the other firms of false advertising, negligence, trespass, creating a public nuisance, potentially endangering the public and monopolistic practices, among other charges. In addition to monetary damages, it seeks injunctions against the sale of dicamba, as well as a requirement that Monsanto take action to remediate the damage from the product.

In a statement issued Friday, Monsanto said it has obeyed all laws in selling dicamba and has worked hard to educate farmers on how to safely and effectively use the product, which was extensively studied by EPA. The company is "confident in growers' ability to follow all application requirements and abide by the law," the firm said.

"The lawsuit is wholly without merit, and we will defend ourselves accordingly," Monsanto said.

In the meantime, Baioni and Joe McLemore, another Crittenden County farmer involved in the suit, must wait until harvest this fall to find out how much the dicamba damage will cut into their already-thin profit margins.

"It's one more thing to worry about going broke over...," McLemore said. "We live on a prayer every year."

Reach Tom Charlier at thomas.charlier@commercialappeal.com or 901-529-2572 and on Twitter at @thomasrcharlier.

ore than a half-dozen farming operations