Farmers Switch Course in Battle Against Weeds

In the age-old struggle between farmers and weeds, farmers have enjoyed the weed killer Roundup. Some have called it the herbicide of a lifetime. But after 30 years on the market the chemical seems to be losing its power over some weeds, changing farming practices nationwide.

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RENEE MONTAGNE, host:

This is MORNING EDITION from NPR News. Good morning, I'm Renee Montagne.

In the age-old struggle between farmers and weeds, farmers have enjoyed an almost magical weapon in recent years: the weed killer called Roundup. Some farmers have said it's the herbicide of a lifetime. But after 30 years of use, that chemical is losing its power over some weeds, which, in turn, is changing farming practices across the country, as NPR's Dan Charles reports.

DAN CHARLES: Ronald Mesick(ph) grows corn and soybeans in flat, sandy soil near Seaford, Delaware. He's been spraying Roundup for decades.

Mr. RONALD MESICK (Farmer): Well, it's used as a burn down to clean up the field.

CHARLES: Roundup, also known by its chemical name glyphosate, kills pretty much all-growing vegetation. So instead of plowing, Mesick uses Roundup.

Mr. MESICK: It just cleans the field up completely so we can go in and plant.

CHARLES: And in recent years, Mesick's been planting Roundup-ready soybeans. The seeds have been genetically altered to survive doses of Roundup, so after the soybeans come up, Mesick can go back into the field and spray again. The weeds die; the soybeans keep growing.

Mr. MESICK: And hopefully that will take care of it until the harvest.

CHARLES: According to Mark VanGessel, specialist on weeds at the University of Delaware, this system is cheap, easy and hugely popular with farmers.

Dr. MARK VANGESSEL (Crop Science, University of Delaware): Probably 90 percent of our soybeans are Roundup-ready soybeans. Roundup-ready corn is on the market. In other parts of the United States, Roundup-ready cotton, extremely popular. Roundup-ready canola...

CHARLES: These crops are controversial. Many consumers and environmental activists reject genetically engineered crops. But in much of the country, according to scientists, Roundup actually has been good for the environment. Roundup-ready seeds made it so easy to wipe out weeds farmers stopped plowing on tens of millions of acres. That keeps the soil healthier and reduces the amount of runoff into streams and rivers.

Also, Roundup is one of the least toxic herbicides. Farmers were able to stop using more dangerous chemicals, as did homeowners and highway departments. Mark VanGessel.

Mr. VANGESSEL: You know, everyone is using glyphosate these days.

CHARLES: And for 30 years, it seemed omnipotent. But about a decade ago, somewhere close to here, a farmer sprayed Roundup on a weed - a stalk of horseweed - and it did not die. Call it the Harry Potter weed, the weed that lived. Nothing to do with magic, though. That plant happened to carry a genetic mutation that made it immune to Roundup. The weed grew and multiplied. And in the summer of 2000, a farmer in Delaware noticed the weeds that wouldn't die. Mark VanGessel went out to look.

Mr. VANGESSEL: There were large areas in the field with plants that were green right next to dead plants, and there was no pattern to it.

CHARLES: After some tests, VanGessel realized he was looking at the countries first major outbreak of weeds resistant to Roundup. There was no containing it. Horseweed seeds are like tiny hot air balloons that can drift for hundreds of miles.

Mr. VANGESSEL: In 2002, it was just all over. That's when I started telling folks, if you've got horseweed in your field, you've got to assume it's resistant. It was so widespread.

CHARLES: Around the same time, other Roundup-resistant weeds started appearing in other parts of the country. So far the resistant strain has appeared in 13 kinds of weeds.

Monsanto, the company that invented Roundup and Roundup-ready crops is watching the situation carefully because it has a huge amount of money at stake. It sells several billion dollars-worth of Roundup weed killer and Roundup-ready seed every year. If this chemical stops working, farmers might stop buying those products. But Michelle Starke, a weed scientist with Monsanto, says at this point farmers are not abandoning their favorite herbicide.

Ms. MICHELLE STARKE (Scientist, Monsanto): I think the important thing to remember is that Roundup or glyphosate does control more than 300 different weed species. And so it does remain the cornerstone for weed control and Roundup-ready cropping systems.

CHARLES: And farmers do not appear to be going back to plowing as a way to kill weeds. What they are doing is using additional chemicals, including some that are more toxic and stay in the environment longer than Roundup. Ronald Mesick, for instance, now sprays Roundup along with one of the oldest chemical weed killers, 2,4-D. And Monsanto is turning its genetic engineers loose on the problem. It's acquired the rights to genes that will allow crops to tolerate two other herbicides called dicamba and glufosinate. If it inserts those genes into corn or soybean plants, too, those crops could withstand a whole cocktail of herbicides. So farmers could spray any of those chemicals and hope that if one doesn't clear away the weeds, another one will.

Dan Charles, NPR News.

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