EPA Deliberates the Fate of Atrazine

• Farmers need pesticides to fight a wide variety of pests.
• Replacing atrazine with alternative herbicides would likely increase overall herbicide use.
• Supporting registrations of pesticides that are safe, effective and economical helps maintain a strong U.S. food supply.

With few new active ingredients coming to market, industry leaders say maintaining registrations of existing pesticides, such as atrazine, is paramount.

“We’d have to pick up those weeds with other herbicides that aren’t as effective and are more expensive. And we would be replacing one product with another product that may not put us at a better place environmentally.”

“We need to have multiple tools available to our farmers,” says Bill Johnson, Ph.D., Purdue University extension weed specialist. “This is especially important in a year like this one where there are supply-chain issues. And when you think about the wide variety of pests and environmental conditions, we need to have multiple tools at our disposal as conditions dictate.”

In Arkansas, where at least one population of Palmer amaranth has resistance to six different herbicide modes of action, keeping atrazine is critical, says Tom Barber, Ph.D., University of Arkansas extension weed scientist.

“We’ve got a lot of five-way resistant populations in the state that are pretty widespread, and atrazine is still one of the only herbicides that is highly effective on those populations,” he says.

A Potentially Costly Loss

Because atrazine is applied mostly to corn, sorghum and sugar cane, its unique mode of action also can benefit weed control in rotational crops such as cotton and soybeans, where it isn’t used.

“It’s part of an integrated approach with crop rotation to help manage our Palmer amaranth,” Barber says. “Taking that away would mean more applications of multiple residual herbicides. We would probably have to make at least three applications just to overlap residuals. A lot of times that would mean two applications more than we’re making now.”

Johnson says the loss of atrazine would make weed control more costly and difficult for Indiana corn and sorghum producers without a guarantee of environmental benefits.

“I think we would really struggle with control of some weeds, like morning glory, waterhemp, giant ragweed, and newly germinated annual grasses that are common in cornfields,” he says. “We’d have to pick up those weeds with other herbicides that aren’t as effective and are more expensive. And we would be replacing one product with another product that may not put us at a better place environmentally.”

Having fewer weed-control options also could increase resistance selection pressure on the remaining herbicides, Johnson says. Already, Indiana has waterhemp populations resistant to four different modes of action, and testing is underway on suspected resistance to a fifth mode. A number of other weeds, including Palmer amaranth, marestail and giant ragweed, have confirmed resistance to multiple modes of action.

Arkansas’ Barber agrees, saying growers in his state would likely apply more pounds of herbicide active ingredient per acre if atrazine weren’t available. It also could confound weed control for growers of non-GMO corn hybrids.

Atrazine allows them to successfully grow a crop using conventional seed, “and they’re getting excellent yields,” he says. “It would possibly make growers move to a technology that has glufosinate.”

But that technology has its own set of challenges as Barber and fellow University of Arkansas weed scientists have identified three Palmer amaranth populations with tolerance to glufosinate.

Benefits to No-Till

In Indiana, about half the acres that receive atrazine are farmed conventionally and half are in some form of no-till or conservation tillage. In those systems, growers keep plant residue on the surface and minimize soil disturbance to significantly reduce soil erosion, Johnson says.

In recent years, no-till production also has been praised for helping store carbon in the soil — benefiting soil health and global warming. The loss of the herbicide could prompt some growers to return to tillage, potentially increasing soil carbon releases, says Mark White, Syngenta senior stewardship and regulatory portfolio manager.

Industry Support

Barber and Johnson were among eight Weed Science Society of America (WSSA) members who submitted letters to the EPA in 2021 supporting the current uses and rates of atrazine. Their comments were in response to EPA’s draft Endangered Species Act biological evaluations for triazine herbicides, which include atrazine, simazine and propazine.

The evaluations are part of the agency’s pesticide registration review, conducted at least every 15 years on each crop protection product or group of products.

The review is just the latest of many that atrazine has undergone since it was initially registered in 1958. Over the years, EPA made several label changes — including designating it a restricted-use material — to better protect workers, the environment and nearby crops.

Caydee Savinelli, Ph.D., Syngenta stewardship team and pollinator lead, says the company continues to support pesticides like atrazine because they are highly effective. They also make sound business sense for both the farmer and the registrant.

As part of that effort, Syngenta updated its atrazine.com website in 2020 to better reflect key safety information, studies and the herbicide’s benefits.

“We know that the public is interested in the safety of their food,” says Chris Tutino, Syngenta senior communications manager. “So, we redesigned the site to help people understand and share the science behind atrazine’s safety that ultimately leads to higher crop production in an increasingly food-insecure world.”

In addition, Savinelli says, safeguarding domestic food production moved into the public spotlight during the pandemic as imports were disrupted — creating supply-chain issues.

“I think it’s important for us to support the American farmer,” she says. “Farmers are business people. They have to make a profit, and the margins on commodity crops are not that high.”

From a weed-control standpoint, Mark White, Syngenta senior stewardship and regulatory portfolio manager, says atrazine continues to perform after more than 60 years of commercial use.

In fact, researchers have conducted more than 7,000 studies on atrazine over the years, making it likely the most-researched pesticide in history.

“The overwhelming scientific consensus points to the safety of atrazine both to human health and ecological health,” White says.

Savinelli and White say Syngenta remains a strong supporter of proactive and regulatory stewardship of its products, including the triazines.

Clarify Public Value

Genevieve O’Sullivan, vice president of communications and marketing for Crop Life America, says one challenge with communicating these types of issues to the public is the frequent use of industry terms, such as no-till or cover crops.

Instead, O’Sullivan likes to demystify the terms. Take sustainability, for example. She defines it as “simply using technology to produce more using less.”

To start the conversation, O’Sullivan says industry representatives need to first listen to the public’s concerns. These approaches are based on consumer research Crop Life conducted during the past three years.

“We actually went out and listened,” she says. “What questions do you have? What are your concerns? That’s how we started the real conversation.”

In addition, the industry needs to take an informational approach, O’Sullivan says, instead of a persuasive one.

“Don’t try to convince anybody of anything,” she says. “It’s important to create shared values.”

Update

On June 30, 2022, EPA announced that it was adopting a new aquatic ecosystem concentration equivalent level of concern (LOC) for atrazine at 3.4 parts per billion (ppb), down from 15 ppb. The scientific and regulatory record completely and categorically refutes this new LOC, says Tutino. For additional information and updates, please visit atrazine.com.