AUDIE CORNISH, HOST:
This past summer, from Mississippi to Illinois, people noticed a curious phenomenon - trees with curled-up leaves or browned needles. That damage apparently came from a chemical, a weed killer that's now popular among farmers. And the Environmental Protection Agency now has to decide whether farmers should be allowed to keep using it. NPR's Dan Charles has the story.
DAN CHARLES, BYLINE: Mike Hayes and I are sitting on the patio of Blue Bank Resort, the business he runs alongside Reelfoot Lake in Tennessee. The sun's going down. The lake is beautiful. But what really catches your eye is the trees standing right in the water along the edges of the lake. Hayes tells me these are 200-year-old cypress trees.
MIKE HAYES: The cypress trees out in the lake - thousands of them. And they're all the trees that was here when the lake was formed.
CHARLES: It was formed by a cataclysmic earthquake in 1812. The earth shook. The land here dropped. And water from the Mississippi River rushed in and covered 15,000 acres of cypress forest. Yet these trees survived and became a home for fish and birds.
HAYES: You know, the fishing's around the tree. The eagles nest in the tree, the egrets. So much wildlife all out in the trees. It just - the trees define Reelfoot Lake.
CHARLES: Last year, though, Hayes noticed the trees didn't look right. The needles were turning brown.
HAYES: Like a burnt brown, curling - you know, something was going on that never happened before.
CHARLES: People started talking. Everybody had a theory - disease, drought, insects.
HAYES: They thought of other things. But when it came down to it, it was a drifting chemical.
CHARLES: A chemical called dicamba. It's a weed killer. And it was blowing in from nearby soybean and cotton fields.
JASON HAMLIN: Ninety percent of the growers use dicamba.
CHARLES: Ninety percent.
HAMLIN: Yes. That's an estimate. I mean, there's nothing exact, but it's a vast majority.
CHARLES: This is Jason Hamlin. He's a crop consultant, helps farmers around here decide what seeds to plant, what pesticides to use. Most have turned to dicamba just in the past two years because weeds have become resistant to other herbicides. And the big seed company Monsanto, now owned by Bayer, created a new generation of genetically modified soybean and cotton plants. They can tolerate dicamba, which means farmers can spray this chemical and the weeds die, but the crops are fine.
HAMLIN: They have to have a tool to control their weeds, or they can't farm, you know?
CHARLES: But dicamba has a problem. Sometimes it vaporizes in the heat and drifts across the landscape. It's damaged other crops, caused battles between farmers, lots of controversy. What's received less attention, though, is the damage to wild plants, the vines in random ditches or trees. A few miles from Reelfoot Lake, I take a little drive with Greg Allen, an agricultural extension agency with the University of Tennessee. It's a country road. On our right - a big field of soybeans. On our left - woodland.
So you have to tell me what catches your eye.
GREG ALLEN: OK. Well, one thing would've caught my eye is that sycamore and them little bitty leaves.
CHARLES: Sycamore leaves normally are wide and flat. These are turned into the shape of a cup. It's the signature of exposure to dicamba.
ALLEN: And you see it goes all the way to the top. That's 30-, 40-foot tree.
CHARLES: I realize almost every sycamore tree here shows this kind of damage. Other kinds of trees, though, don't. And it varies from state to state, too. In Iowa, forestry experts haven't found much damage. In Arkansas, though, a scientist that state officials hired to conduct a survey found signs of dicamba on trees in every town that he visited. And the EPA has to decide by the end of the year what to do about this, whether to let farmers keep using dicamba on their crops.
There are billions of dollars at stake. Monsanto's arguing the government cannot take this tool away from farmers. They need it. If used properly, the company says, it doesn't hurt anything but the weeds. Back at Reelfoot Lake, Mike Hayes says his brown cypress trees show the opposite. He thinks state politicians are ignoring the problem partly because they're scared of Monsanto.
HAYES: The problem with dicamba - there's so much money behind it. I've never seen so many people run from a problem so bad in my life. I mean, it really, really hurts to lose something like we're about to lose.
CHARLES: Dicamba hasn't killed the trees, he says, but with time it could. And new ones can't sprout and grow out there in the water. If these cypress trees die, they're gone forever. Dan Charles, NPR News.
NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.