Farmers Learning Limits of Popular Herbicide
24 January 2012
This is the VOA Special English Agriculture Report.
Pigweed spreads fast and grows as tall as two meters. This weed can overpower cotton and other crops. It comes from the amaranth family and is also known as Palmer amaranth or Palmer's pigweed.
A cultivated version of amaranth is grown for food and medicine in Africa and Asia. In the United States, some people buy amaranth as a gluten-free substitute for wheat flour. But wild pigweed is a big problem in cotton-growing states in the South. And now the plant is spreading into the Midwest.
Cotton plant
In many cases the pigweed is killing genetically modified cotton and soybeans. For years farmers could control it by spraying with
But weed scientist William Curran at Pennsylvania State University says over the past three or four years, pigweed has become resistant to glyphosate. Now, farmers in some areas can no longer depend on that popular herbicide alone to defend against pigweed.
WILLIAM CURRAN: "When a weed is resistant, either the herbicide that it is resistant to has no effect at all or, you know, it might have some effect, but usually not enough to kill it."
He says farmers can try other herbicides. Or they can mix another herbicide with Roundup and use the mixture when they would normally spray their fields.
WILLIAM CURRAN: "The reality is even though have this weed, this one one weed that is resistant, there's still a lot of other weeds that Roundup still kills."
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