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The Jargonaut: 2,4-D? Come Again?
What's that collection of numbers and letters all about? Get to know the next big, bad pesticide in conventional agriculture.

2,4-D (n.): an herbicide popular in both agriculture and lawn care

Farmers and weeds are in an arms race. Soon after a new herbicide emerges, weeds start evolving ways to defeat it. Eventually, the product becomes useless, forcing manufacturers to concoct an even more powerful pesticide.

Roundup, the world’s most famous herbicide, hit the U.S. market in 1976. Paired with crops genetically engineered to tolerate it—such as “Roundup-Ready” corn and soybeans—Roundup soon became the kind of commercial success most companies can’t even dream of. Farmers and homeowners now spray tens of millions of pounds of Roundup every year. In 1994 a trade journal named it among the “Top Ten Products that Changed the Face of Agriculture.” Despite claims that the chemical causes rashes, hormone disruption, attention deficit disorder, and cancer, many growers called Roundup a “godsend.”

Can you see where this is going? Roundup has stopped working. Weeds soaked in the herbicide develop resistance, and Roundup is currently dying a slow death—the victim of its own success. Farmers are looking for a new miracle herbicide.

Enter 2,4-dichlorophenoxyacetic acid. Nicknamed 2,4-D, this herbicide lacks a catchy commercial moniker like Roundup. It isn’t exactly new, either:

Despite the chemical’s 67-year-history, weeds haven’t yet developed strong defenses against 2,4-D, making it a candidate for the next big thing in herbicides.

Like Roundup, however, 2,4-D comes with its fair share of controversy. The non-profit Environmental Working Group cites research linking the synthetic chemical to cancer, immune system dysfunction, and several other disorders. 2,4-D was also a component of the infamous herbicidal cocktail Agent Orange, which the United States used during the Vietnam War to destroy thick vegetation in the jungle. Although the best evidence suggests that an ingredient other than 2,4-D is responsible for numerous diseases that have since been linked to Agent Orange, companies typically don’t want their products to have such an infamous association.

Just as Monsanto engineered plants that can tolerate Roundup, Dow AgroSciences has developed genetically modified crops to withstand heavy exposure to 2,4-D (see “Super Weeds and Wonder Worms”). On Wednesday, the U.S. Department of Agriculture approved commercial planting of “2,4-D-ready” corn and soy despite the objection of several health and environmental advocacy groups, including NRDC (which publishes OnEarth).

Critics say the weedkiller is associated with several human diseases, has been found in drinking water, and can drift between fields, damaging non-GMO crops. The USDA’s approval of these new resistant crops could more than triple the amount of 2,4-D sprayed in the next six years, putting the herbicide on the same path of overuse and eventual obsolescence as its predecessor.

More lawsuits are sure to follow. You’re about to hear a lot more about 2,4-D.

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Brian Palmer covers daily environmental news for OnEarth. His science writing has appeared in Slate, the Washington Post, the New York Times, and many other publications. MORE STORIES ➔