A little-known disease could be at the root of the root rot problems besetting pea crops in Saskatchewan.
Farmers have been complaining that their pea yields are declining, prompting Saskatchewan Pulse Growers to launch an investigation.
The data shows that the provincial average yield has not been falling, but yield variability has increased in certain parts of the province, with growers experiencing either fantastic or abysmal yields.
Sabine Banniza, a plant pathologist at the University of Saskatchewan’s Crop Development Centre, has a hunch what’s behind the increased variability.
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“I wouldn’t be surprised if aphanomyces in certain areas may be responsible for quite a bit of what we have seen because conditions were just so right,” she said.
Aphanomyces euteiches is a form of root rot that affects legumes such as peas, lentils and alfalfa.
The disease had been reported in Manitoba and Alberta but hadn’t been found in Saskatchewan until Banniza began investigating the pea yield problem last summer.
She took samples of diseased pea roots from the Medstead area in crop district 9AW, the Swift Current area in 3BN and the Assiniboia area in 3ASW.
Banniza confirmed through molecular identification that aphanomyces was present in all three crop districts. Farmers had complained of poor yields in those districts.
Banniza thinks the disease has been lurking in the soil for years because of how widespread it was in Saskatchewan.
“We assume it just sort of experienced a population explosion with the extreme rainfalls we’ve had in the past few years,” she told growers attending the pulse portion of Crop Production Week.
“It is basically raising its ugly head.”
Aphanomyces is a fungus-like organism that thrives in soggy soil.
“The spores it produces can actually swim,” said Banniza.
When Banniza broke down the data she discovered that spring was exceptionally wet in all three districts in 2010, 2011 and 2012.
The flooding, water logging and soil compaction would have created ideal conditions for the disease.
However, Banniza said the disappointing pea yields are unlikely a one-issue problem.
Peas perform poorly under wet conditions even if no pathogens are present.
As well, other root diseases such as fusarium, rhizoctonia and pythium were contributing factors, she said. Aphanomyces could be back next year if there is another wet spring.
No seed treatments are available and producers’ only option is to avoid planting peas on infected fields for at least four years and possibly as many as 10 years.
