Jul 23, 2012
Herbicide-tolerant crops spark concerns

In 2008, Dave Simmons’ neighbor applied 2,4-D on a windy day.

He shouldn’t have been spraying. The herbicide drifted onto a 2-acre block of Simmons’ grapevines, stunting their growth and hurting yields for the next two seasons. The damage was substantial, Simmons said.

The next year, the state chemist visited Simmons Winery in Columbus, Ind., and determined what caused the injury. Simmons filed a claim against his neighbor’s insurance company, which paid for the damage to his grapevines. Relations became a little awkward with his neighbor, but at least he stopped using 2,4-D, Simmons said.

Simmons hasn’t had any problems with drift since, but he still finds herbicide damage on his crops every year. The culprit is most likely volatilization – when the active ingredient in an herbicide evaporates into the air.

Simmons isn’t the only specialty crop grower in Indiana — or the rest of the Midwest — who has had to deal with damage from the off-target movement of pesticides. For those who grow sensitive crops in an ocean of corn and soybeans, it’s an ever-present problem.

And it could worsen in the next few years, if the anticipated release of new herbicide-tolerant crops comes to pass. The Save Our Crops Coalition (SOCC), which Simmons recently joined, was created in December to rally grower groups, produce companies and others concerned about the impending releases.

According to its website (www.saveourcrops.org), SOCC was organized “for the specific purpose of preventing injury to non-target plants from exposure to 2,4-D and dicamba.”

SOCC Chairman Steve Smith said genetically modified crops working their way through the regulatory process could lead to a massive increase in the use of dicamba and 2,4-D. Such a spike could be a grave threat to sensitive specialty crops, including tomatoes and grapes.

Smith said Dow AgroSciences is planning to release 2,4-D-tolerant corn in 2013 and 2,4-D-tolerant soybeans in 2014. Monsanto Co. and BASF plan to release dicamba-tolerant soybeans in 2014.

“Our coalition is not opposed to genetic modifications for crops, and not opposed to the use of crop protectants,” Smith said. “Our only concern is off-target movement. That’s a rational and reasonable concern that absolutely needs to be addressed.”

As director of agriculture for Red Gold, a tomato processor based in Elwood, Ind., Smith has a vested interest in SOCC’s goals and protecting his company’s suppliers, who farm in the Midwest. The South could also be vulnerable, with manufacturers there hoping to launch dicamba- and 2,4-D-tolerant cotton within a few years, he said.

Off-target movement

Both 2,4-D and dicamba have been around for decades and were extremely volatile when first released. Adjustments in formulations over the years have gradually reduced that volatility. Manufacturers have also changed label instructions and improved application techniques, seeking to reduce the amount of damage the herbicides can effect on specialty crops, said Dave Mortensen, a weed ecologist with Penn State University.

It’s tough to quantify damage that off-target movement of pesticides can perpetrate. Much depends on conditions during application and the timing of exposure. If grapes, for example, are exposed after bud break but before bloom, damage can be significant and include reduction in vigor and delayed ripening. If it happens every year, it’s not a sustainable situation, said Bruce Bordelon, a horticulture professor and Extension specialist with Purdue University.

The worst cases usually result from drift, which can be hard to avoid, Bordelon said. Applicator error is the No. 1 cause.

“Drift happens every day on every application,” he said. “You almost can’t spray something and not have it drift somewhere off target.”

While drifting a few feet is no big deal, drifting over the fencerow into a neighbor’s field is another matter, he said.

Better spray technology, such as drift-reducing nozzles and smaller droplets, can help curb drift. Purdue created the DriftWatch website (www.driftwatch.org) to address the problem as well. By mapping pesticide-sensitive areas in several Midwest states, the site has helped to curb drift problems, Bordelon said.

Even though major drift incidents can be avoided by using proper application practices, an herbicide can still volatize and end up in a field two miles away, Simmons said. 2,4-D can do major damage through volatilization, and still be nearly impossible to pinpoint its source. There’s little recourse when crops are damaged that way, the grape grower said.

“Over the years, I have experienced several instances where an herbicide has volatilized and moved to my fields, damaging our fresh-market vegetable crops,” stated Jody Herr, a grower of fresh-market vegetables in Indiana, on SOCC’s website. “With the possibility of an even longer application window and increased usage of these products, I fear the occurrences of volatilization and direct drift will continue to escalate.”


SOCC calls 2,4-D “the nation’s most dangerous pesticide for non-target crop damage.”

In response to such concerns, Dow AgroSciences has developed a new formulation of the herbicide, called Enlist, that isn’t as volatile as past formulations. Enlist products should reduce drift and volatilization by about 90 percent, said Garry Hamlin, a Dow spokesperson.

“We’ve been in discussions with concerned stakeholders, and we think the product we have has met their needs,” Hamlin said.

There’s a way to avoid the dangers of those older formulations, Hamlin said. When growers buy 2,4-D-tolerant corn, for example, Dow plans to make them sign an agreement that would not allow them to spray generic 2,4-D formulations over the crop, only Enlist products.


Dicamba is cheap and effective, but corn growers don’t use it much because they don’t want to hurt neighboring soybeans, which are susceptible to damage from off-target movement of the herbicide. If those soybeans happened to be tolerant to dicamba, however, corn growers’ use of it would “skyrocket.” The soybeans would be fine in that case, but nearby specialty crops wouldn’t, Smith said.

Monsanto and BASF have partnered on the release of dicamba-tolerant soybeans. Other dicamba-tolerant products are in development as well, said Kim Magin, director of industry affairs for Monsanto.

The two companies are also working to develop low-volatility formulations of dicamba and to restrict use of the more volatile formulations. They’ll take steps to educate and train growers so they’ll use best practices when applying the products and will follow the proper label requirements, Magin said.

Mortensen isn’t convinced that improving application techniques will be sufficient. It’s difficult to adhere to weather-condition constraints, for example, when there are a lot of corn or soybean acres to cover and only a narrow window of time to get the job done, he said.

As with 2,4-D, some formulations of dicamba are less volatile than others, but that won’t keep some growers from using the more volatile formulations, Smith said.

Cumulative effects?

There’s another potential consequence of increasing the use of these herbicides, Mortensen said. It’s not clear what, if any, cumulative effects it could have. Herbicide drifting from one field into another is bad enough, but what about herbicide from 22 fields? How much damage would that do to specialty crops?

Those questions haven’t been studied very critically, Mortensen said.

By Matt Milkovich, Managing Editor


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