At a press briefing during their company's weed resistance conference in Miami this week, Bayer officials on a panel were asked if they saw parallels between heavy use of the corn herbicide atrazine 40 years ago with the dominance of glyphosate today.
The questioner recalled that in the late 1960s, atrazine and other triazine herbicides had burst upon the corn industry like a tornado. Journalists were taken on farm tours where they checked out corn fields cleaner than they'd ever seen. Growers planted corn on corn with never a thought about weed buildup.
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| Growers in the U.S. and elsewhere are managing their atrazine use to maintain the herbicide’s longer-term efficacy. This buffer zone of native grasses was installed to keep atrazine out of runoff. -- Photo by Chung-Ho Lin, courtesy USDA/ARS. |
Then came disillusionment. Weeds rapidly developed resistance. Application rates had to be increased, and even then there were escapes. Before long, it was confidently predicted, triazine herbicides would be history.
But they're not. More that 40 years later, they're still a key component in the weed control program of many corn growers. What happened?
Panel members explained that the resistant weeds didn't go away. They're still around. But the way growers used triazine herbicides changed.
Today they're used in combination with many other herbicides, at lighter rates, over a narrower application window. Growers have moved away from continuous corn, and triazines now tend to be reserved for use against weeds on which they are especially effective. That way, triazine-tolerant weeds have less opportunity to multiply and spread.
Does glyphosate face a similar future? While noting some fundamental differences between the two herbicides, the Bayer officials also saw similarities. Even with the emergence of resistance, they ventured, glyphosate will remain an important weapon in farmers' weed control arsenals for many years to come.
Just how important, they added, will depend on how sustainably the herbicide is used and managed by farmers in the next few critical years, and how successful the crop protection industry is in developing substitute and complementary products to take the pressure off glyphosate.