Roundup Ready canola becomes a problem weed in California

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Two UC Cooperative Extension farm advisors have found that Roundup Ready canola can be overly persistent in California, according to an article in Western Farm Press.

Doug Munier of UCCE in Glenn County and Kent Brittan of UCCE in Yolo County studied the herbicide-resistant oil crop to determine its potential for biofuel. However, they found that yields were too low to make canola a profitable irrigated California crop.

"They gave up on canola, but canola did not give up on California," wrote Farm Press editor Harry Cline. "It is still around in many fields, three or four years after it was grown as a commercial crop."

The problem is canola's tendency to shatter. Seed matures from the base of the stem sequentially up to the top of the main stem. By the time the seed at the upper part of the plant is mature, the pods at the bottom of the plant will likely have fallen to the ground, or "shattered."

Munier told the reporter that a significant percentage of canola's "shattered seed" does not germinate the following year. When the shattered seed is incorporated into dry soil, it creates secondary seed dormancy.

As an example, Munier related the experience of a Sacramento Valley farmer growing Roundup Ready alfalfa.

“The grower sprayed his Roundup Ready alfalfa and got beautiful weed control except for what he thought was mustard. The herbicide did not touch it," Munier was quoted in the story. "His PCA looked closer and discovered it was Roundup Ready canola. Recognizing the problem, he rogued out the canola."

For a trial in the Chico area, Munier planted Roundup Ready canola in the fall of 2006. Harvested the next summer, the field was summer fallowed in 2007 followed by fall-planted wheat. Roundup Ready canola volunteers from the 2007 harvest are still sprouting in 2010.

“This is not just a weed, but one totally resistant to Roundup, a herbicide that is intensely used in a wide variety of high value crops in California,” Munier told the reporter.

Canola reseach plot.