Bloomberg News

Brazil Soybean Farmers Seen Facing Spread of Invasive Pigweed

November 19, 2012

Brazilian soybean farmers are facing a spread of invasive weed species, particularly herbicide- resistant pigweed, according to Soybean & Corn Advisor Inc.

Pigweed may have become a significant problem on several million hectares in southern Brazil, the Hinsdale, Illinois- based industry researcher wrote in an online report today. Herbicide-resistant pigweed has yet to be found in Mato Grosso state, it wrote.

Brazil is expected to overtake the U.S. as the largest soybean exporter in the 2012-13 season, the U.S. Department of Agriculture forecasts. Widespread use of Roundup Ready soybeans and Roundup herbicide led weeds to become resistant in the South American country, according to Soybean & Corn Advisor.

“Weed control in the soybean fields of Brazil was easier in years past because of a general lack of invasive weed species,” the researcher wrote. “After several decades of monocrop soybean production and the use of a single herbicide, weed control in Brazilian soybean fields has become more difficult and more expensive.”

Three or four pigweed plants per square meter can cause crop losses of as much as 10 percent, Soybean & Corn Advisor wrote. The spread of Roundup-resistant weeds raised farmers’ costs by forcing them to apply a cocktail of herbicides to keep unwanted plants under control, according to the report.

Central Brazil has no freezing temperatures to kill off weeds, and warm weather during the dry season allows the plants to grow year round, the researcher wrote.

A hectare equals 2.47 acres and a square meter equals 10.8 square feet.

To contact the reporter on this story: Rudy Ruitenberg in Paris at

To contact the editor responsible for this story: Claudia Carpenter at

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