Monsanto Co., the biggest seed maker, said the bushy plant Kochia is no longer being killed by the company’s Roundup in parts of Canada, a sign that resistance to the world’s best-selling herbicide is spreading.
Kochia that resists glyphosate, the active ingredient in Roundup, was confirmed in three fields in southern Alberta, St. Louis-based Monsanto said yesterday in a statement on its website. The weed, which can thrive in drought conditions and grow 7 feet tall (2.1 meters), previously was found to be glyphosate-resistant in three U.S. states, the company said.
Glyphosate-resistant weeds have spread with the popularity of Monsanto’s Roundup Ready crops, which are genetically modified to withstand applications of the herbicide. To combat the problem, Monsanto and its rivals are engineering crops that resist additional weed killers such as dicamba and 2,4-D, an ingredient in the defoliant Agent Orange.
Kochia resistance in Alberta affects 101 to 500 acres, according to the website of the International Survey of Herbicide Resistant Weeds.
The Canadian case is different from most because the kochia, found in fallow fields, don’t appear to have developed resistance on farms where Roundup Ready crops were regularly planted, Monsanto said. Still, the weeds “could present new challenges” on Alberta farms that use Roundup Ready canola and sugarbeet seeds, the company said.
In the U.S., Roundup-resistant weeds such as kochia and Palmer amaranth have invaded 14 million acres of cotton, soybean and corn, and that will double by 2015, Syngenta AG said last year. A Dow Chemical Co. study in 2011 found as many as 20 million acres of corn and soybeans may already be infested.