Glyphosate-resistant weed spreads to Canada crop belt

A weed resistant to a widely used chemical to protect crops has spread for the first time to Western Canada, the country's grain and canola belt.

Kochia weed turned up in three fields in Southern Alberta last August, despite the use of glyphosate, and Canadian government scientists have now confirmed that it is resistant to the farm chemical, seed company Monsanto Canada said on Wednesday.

So-called "super weeds" have defied dosages of the world's top-selling herbicide, Monsanto's Roundup, and spread through key crop-growing areas of the United States in recent years, boosting costs and cutting crop yields for farmers.

Roundup's active ingredient is glyphosate.

"That is one of the chemicals that has been so broadly used that this will be a growing issue that we have to face," said Ron Frost, a Calgary, Alberta-based agriculture analyst.

Kochia has previously been confirmed in Kansas, Colorado and Nebraska, and suspected cases are under investigation in North Dakota, South Dakota and Montana.

The southern Alberta case is unique because it does not appear to have developed in a field where farmers regularly grew Roundup Ready crops, which are genetically modified to tolerate Monsanto's weed-killing herbicide, the company said.

The fields were left fallow last year to replenish soil nutrients, and chemicals were used to control weeds.

Resistance typically evolves after farmers use the same herbicide repeatedly on a weed population, without other approaches to control weeds, Monsanto said.

"We recognize this particular finding could present new challenges if it spreads because of the prevalence of Roundup Ready canola and Roundup Ready sugarbeets in this region," said Sean Dilk, Monsanto Canada's technology development manager. "But the effective use of Roundup agricultural herbicides and Roundup Ready crops has continued in areas where glyphosate resistance has occurred in the past."

Canada is the world's biggest exporter of spring wheat, canola, durum and malting barley, all of which mostly grow in the western provinces.

The Alberta case is unlikely to sway farmers in that area away from planting canola, even though Roundup Ready canola is one of the most popular seed varieties, Frost said. But he added the super-weed's spread is "a big deal" for the future of seeding canola, which is Canada's second-largest crop after spring wheat.

The case is a warning to farmers not to overuse any farm chemical, said Murray Hartman, oilseed specialist for the Alberta government.

Farmers in the affected region may now look to alternate seeding of Roundup Ready canola with Bayer CropScience's Liberty Link canola, Hartman said.

BASF also produces a herbicide-resistant canola, called Clearfield.

Two other resistant weed species, giant ragweed and Canada fleabane, have previously been confirmed in Canada, both in southwestern Ontario.