Root rot declines

Root rot was not as big a problem in 2017 as it had been in previous years, says Agriculture Canada.

“The big story of 2017 was obviously that it was a much drier year and we did see the effect of that dry year on root rots,” said Syama Chatterton, research scientist with Agriculture Canada.

While 80 to 90 percent of the 250 pea fields and 120 lentil fields tested across the prairie region tested positive for some form of root rot, the severity of infection was far lower than it has been in wet years, especially for lentils.

In Alberta, 32 percent of the pea fields had a moderate to severe root rot infection. The mean severity was 2.9 on a scale of one to seven, with anything above three considered moderate to severe.

In Saskatchewan, 43 percent of pea fields had moderate to severe infection with a mean severity rating of 3.4.

The numbers were similar in Manitoba with 36 percent moderate to severe infection and a 3.3 severity level.

Moderate to severe aphanomyces infections were found in about 25 percent of the pea fields across the Prairies. Aphanomyces is the most damaging form of root rot in pulses.

Root rot was as prevalent in lentil fields as it was in pea fields but the severity of the infection was far less severe.

In Alberta, just three percent of fields had moderate to severe root rot infection levels and the mean severity was two.

Eight percent of the fields tested in Saskatchewan had moderate to severe infection and the mean severity was 2.1.

Manitoba doesn’t grow lentils.

There was no aphanomyces detected in Alberta’s lentil fields, while 20 percent of the fields in Saskatchewan had moderate to severe infection levels.

So why did the lentil crops fare so much better than pea crops in 2017?

“That is a really good question and I think something that surprised us,” said Chatterton.

Her hypothesis is that lentils are primarily grown in the brown soil zone where the dry conditions were most acute last year.

In general, 2017 was a pretty mild year for root rot compared to wet years such as 2014 and 2016.

But she doesn’t think that will be a predictor of what happens in 2018. While last year’s pea and lentil roots will not have produced as much inoculum as in past years, there is still plenty of it in the soil and if 2018 turns out to be a wet year, the disease will come roaring back.

Chatterton also doesn’t believe that reduced pulse acres in 2018 will have much impact on the disease.

Agriculture Canada forecasts a two-million-acre reduction in pea and lentil plantings, but she thinks a lot of the decrease will be on farms that just recently started growing pulses and those farms don’t have much problem with the disease anyway.

Chatterton said 2017 was the last year for the root rot survey because researchers now have a good grasp on the extent of the problem.

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