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Herbicide-Resistant Weed a Growing Concern to Cotton Growers

A new weed has been sweeping through cotton fields- one that is herbicide-resistant, spreads easily, and can grow an inch a day even during harsh or dry conditions. It is the Palmer amaranth, a pig weed that can grow 6 to 10 feet tall. And it has made its appearance in five of the 16 states where cotton is grown and in almost 50 farms, some of which have had to be completely cut down. Amaranth is resistant to the most common pesticide used on cotton, glyphostate (most commonly known as Roundup by the Monsanto Company). This has caused great concern to cotton growers, who might have to resort to using a combination of heavier herbicides, which will be expensive and problematic.

Alan York, a weed scientist at North Carolina State University emphasized the seriousness of the Palmer amaranth. "It is potentially the worse threat since the boll weevil," referring to a beetle that caused great damage on the cotton industry in the early 20th century and forced many farmers to turn to other crops. "If someone were trying to design a particularly nasty weed, Palmer amaranth could be the model," York said.

The boll weevil was eradicated in the late 1970s, which allowed cotton to return to being a major cash crop. The cotton industry was revolutionized again in the 1990s through the introduction of BT cotton - genetically engineered cotton with its own built-in pest defenses. Monsanto also introduced Roundup Ready cotton—cotton that wouldn’t perish with the weeds when sprayed with glyphostate herbicide.

These scientific developments in pesticide technology allowed cotton growers to radically reduce the amount pesticides used and to switch to conservation tillage, which is minimal cultivation of the soil. This reduces soil erosion and helps to retain soil moisture. York said that Roundup has been “so good, so economical and such a benign herbicide, that we became dependent on it... But when you rely too heavily on one technology, resistance will eventually develop.”

Scientists have long questioned the sustainability of this new reliance on herbicides. Before the advancements in herbicides that allowed for conservation tillage, farmers often had to plow the field to bury weeds and their seeds and in addition to spraying heavy chemicals to protect the crops from pests. This process was time-consuming, expensive, and difficult on the soil.

Some farmers say that the emergence of herbicide-resistant weeds can cause grave environmental consequences. Many are looking to Monsanto for guidance, which posts news and tips for cotton farmers on its website.

What is clear is that the glyphostate-resistant weed is the natural consequence to an industry increasingly reliant on this herbicide.

“We can for sure say it’s going to cost more money,” said York. “You’re going to have more herbicides to try to beat it back. Is it going to put us out of the cotton business? I hope not, but it’s going to make it more challenging.”

Source: Associated Press

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December 6, 2019, 12:36 pm PDT

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