Relaxation of canola rotation restrictions in some Alberta counties isn’t a green light to return to short rotations, agronomists say.
The threat of clubroot damage has been reduced through the introduction of Pioneer Hi-bred and Monsanto clubroot resistant crops.
As a result, there is less need for producers to use long rotations between canola in some Alberta counties where the fungus first appeared as a yield limiter.
Some heavily infested Alberta counties have shifted to voluntary codes of practice from canola restrictions.
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Clint Jurke of the Canola Council of Canada said producers who are considering returning to two or three year canola rotations should study the consequences of that choice.
Alberta crop insurance data shows that the highest yields come from three and four year canola rotations.
“That’s where the money is. And by shortening up the rotations, especially in those areas that are already (carrying a higher pathogen load), farmers are creating the secondary yield problem of breaking down the resistance in these new R-rated canolas,” said Jurke.
“Tight rotations allow the clubroot to continue to spread. And that creates an environment where the pathogen will have the opportunity to test that genetic resistance in the R-rated varieties,” he said.
“We don’t have the research to say that the two new varieties’ genetic resistance is diverse enough to ensure that one can be alternated with the other to help reduce adaptation by the clubroot. But until we do, it might be one more way to reduce the threat of breakdown. Pioneer one year and two or three years later, the Monsanto,” he said.
“Researchers are trying to determine how many different races (of clubroot) there are in Alberta right now. The more races, the greater the risk the disease will overcome R varieties,” he said.
When Mendel, the European resistant, winter variety, was released in 2002, British growers returned to short rotations and by 2007, the disease had overcome the resistance provided by those genetics.
“If I was pushing my rotations in an infested area, I sure wouldn’t want to be that first farmer to be identified as developing the strain that overcame the Rs,” said Jurke.
