Atrazine: Controversial weed-killer still used in Western Kentucky

Although most European countries have banned it, the pesticide atrazine is used in Western Kentucky’s corn-rich fields for two reasons: It’s cheap, and it works.

Atrazine, one of many synthetic herbicides, kills cocklebur, morning glory and giant ragweed, the three weeds most likely to reduce state corn production, says William Witt, a plant and soil science professor at the University of Kentucky. The herbicide essentially starves the roots of these weeds, while corn can break atrazine down until it is no longer potent.

Weeds are a particular problem for state corn growers because we straddle the line between north and south. “We’re in a transition zone,” says Jim Martin, a weed control specialist for UK in Princeton, Ky. “We get the worst of both worlds.”

Most of the atrazine sold statewide goes to commercial and private corn-growers for anywhere from $3.50 to $6 per acre. At those prices, it’s no wonder atrazine has been the main method of weed control for the roughly 1.5 million acres of corn grown in Kentucky each year since the 1960s.

You can’t walk in and buy atrazine off the shelf, and even if you could, you’d have to be trained and certified.
Because it can leach into surface water via runoff, the EPA has deemed atrazine one of 300 restricted-use pesticides, and Kentucky’s Department of Agriculture heavily regulates how it is sprayed on cornfields, says Ernest Collins, who studies water quality as it relates to pesticide use in Kentucky for the department’s environmental services branch.

“We want farm products out there that are used properly,” Collins says.

To be certified to spray a restricted use pesticide, commercial and private growers must pass an exam, and certified growers must attend classes on restricted use pesticides as part of the state’s continuing education.

In Kentucky, atrazine is often paired with other pesticides for weed control, but it cannot be mixed or sprayed within 50 feet of a lake, stream, river or reservoir. Farmers must rinse out sprayers in their fields, not in a well or any other public water source. Unlike Florida, you can’t use it for gardening. Retail outlets that do carry it are subject to state inspection and using it for purposes besides killing weeds is a felony.

But for University of California-Berkeley biologist Tyrone B. Hayes, that’s the least of atrazine’s problems.
In the documentary “For Love of Water,” which premieres at Baxter Avenue Theatres on March 21, Hayes explains that he was asked by Syngenta, the Switzerland-based agribusiness corporation that is now the largest maker of atrazine, to find out whether it disrupts endocrine systems in frogs.

In the study, completed in 2002, Hayes and a team of researchers concluded that atrazine does upset the balance of testosterone and estrogen and increases estrogen production, which effectively castrates frogs.

Collins says the EPA has been unable to validate the integrity of Hayes’ research, hinting at problems with its comprehensiveness. “There’s more than just herbicides that will affect an amphibian,” he says. “Did he look at all the effects taking place at the time from other outside sources?”
Hayes has posted extensive research on atrazine at

Love wasn’t what Crittenden County officials thought in May 1999, when they learned that atrazine levels in the county’s two manmade lakes — Lake George and Old City Lake — exceeded the maximum contaminant level of three parts per billion, by a factor of 10.

 In response, the district created a city lakes cost-share program.
The 70 farmers inside the county’s 3,200-acre watershed are eligible for a recurring state grant of $7,500. The grant helps farmers pay for building natural filtration buffers, such as 50-foot grass waterways, which dilute pesticides, or to convert their farms from cropland to grassland or to use alternative pesticides.

Every year, most of the grant is spent on atrazine alternatives, says Larry Starr of the USDA’s Natural Resource Conservation Service in Livingston County.

As of now, all of the farmers in the watershed have stopped using atrazine and, since 2001, both lakes haven’t seen an increase above three ppb.

“They’re all taking advantage, not because they’re getting incentives from it,” Starr says, “but they realize they were polluting the drinking water.”

State agriculture experts say that while they are aware of atrazine’s environmental and biological effects, the levels showing up in Kentucky’s surface water are not only benign, they’re virtually nonexistent.

Less than 1 percent of the atrazine sprayed leaves Kentucky cornfields in large part because of a practice called no-till conservation farming, Witt says. Corn is planted in the previous year’s crop stubble, thereby preventing soil erosion and lowering the likelihood of pesticides creeping into soil and, eventually, streams and rivers.
“If we stop soil erosion, we stop any kind of contaminant that goes along with the soil,” Witt says.

The EPA blessed it further in its 2003 report on chlorotriazines — the basic chemical structure of atrazine — saying it met all safety criteria for a restricted-use pesticide.

There are, however, signs that this magic bullet might have finally hit a wall.
Atrazine sales in Kentucky have fallen since 2003, Collins says, and last year, nearly a fourth of all U.S. corn growers were planting Roundup Ready corn, which makes a protein that allows it to thrive in the presence of the pesticide glyphosate, Roundup’s chemical name. Glyphosate isn’t as water-soluble as atrazine, and therefore poses less risk to groundwater and surface water, according to a University of Maine study.

Nature might also be playing a role in the decline. Since soil develops a resistance to a particular pesticide over time, farmers will continue to move toward other options for weed control, Collins says.

Collins predicts, though, that atrazine use won’t stop entirely. Syngenta and the EPA are in the final year of a five-year “Interim Registration Eligibility Decision,” to monitor pesticide levels in water throughout the country.

If atrazine levels rise above 37.5 parts per billion — a threshold set by the EPA — its use could be in question, but so far, it hasn’t. Once the five-year study is up, Collins says it could be 2009 or even 2010 before the EPA makes up its mind about atrazine usage, because it will take that long to evaluate all the data it and Syngenta are collecting.

“Right now, unless EPA finds something in that IRED, I look for it to still be used,” he says. “It’s like any other chemical used out there. The EPA has done enough monitoring that they feel that it should continue to be used.

“We’re talking about chemistry and biology,” he says. “The use of pesticides in farming is a privilege, and it’s up to people use it correctly.”

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