RR Canola Evolves Into Vexing Weed

There is a new glyphosate-resistant weed. It is so new it’s not anyone’s fault.Cannot blame this one on overuse of Roundup or poor weed resistance management.

It’s a volunteer that in California blindsided farmers and researchers.

It is Roundup Ready canola, a crop that turns into a weed if you are not careful.

Canola shatters badly during harvest. University of California Cooperative Extension farm advisors Doug Munier in Glenn County and Kent Brittan in Yolo County knew that when they became part of team testing RR canola as a possible oil crop for biofuel.

Munier, Brittan and others found yields too low to make canola a profitable irrigated California crop at current prices. They gave up on canola, but canola did not give up on California. It is still around in many fields, three or four years after it was grown as a commercial crop.

Canola shattering losses can potentially be huge.

However, there is far more to it than that.

“What makes canola a different critter is that a significant percentage of this shattered seed does not germinate the following year, which is very different from other California field crops,” Munier explained. “When the shattered seed is incorporated into dry soil, it creates what is called secondary (seed) dormancy.” This is a common genetic trait for canola.

A canola crop that yields 1,400 pounds per acre would produce the equivalent of 182 million seeds per acre or 4,177 seeds per square foot, according to one Canadian researcher. Irrigated California canola has yielded 3,000 pounds per acre. A little shatter goes a long way.

From a 5 to 10 pounds per acre crop seeding rate, Munier said, shatter at harvest can produce up to 10 times the initial seeding rate to fall on the soil to germinate for years to come.