Slow spring increases root rot risk

Early-seeded pulses may be setup for root rot concerns this year, given the cold spring and saturated soils

Mud may have kept you out of fields this spring, but pulse experts warn that root rots might be plenty active under the surface.

Cool temperatures and soil moisture curbed producer efforts to access fields this year. The province estimated that only nine per cent of seeding was complete in Manitoba after the first week of May, less than half of what was completed the same time last year. By the third week of May, provincial extension staff noted the upper inches of soil were dry, but that deeper soil was still wet enough to keep some producers out of the field.

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Why it matters: Growers were anxious to get crops in the ground as May dragged and fields stayed too wet for seeding, but early pulses like peas may also be in for disease worries, given the rough start.

The cool, wet start will have elevated disease risk for whatever pulses were seeded prior to the last few weeks of May, provincial field crop pathologist David Kaminski warned.

“The condition that we’re starting off with this year is cooler soil and a wetter condition and that can be a stressful situation for any crop that’s emerging or planted and slow to emerge because of those conditions,” he said. “That will be the time when all root rot pathogens that are in the soil may be able to take hold and cause problems for the longer term.”

Field peas, as an earlier-seeded pulse, are of particular concern, particularly if producers did not opt for seed treatment.

The province reported some peas in the ground as of May 12, following a week of consistent overnight lows below freezing.

In comparison, few soybeans were in the ground prior to the May long weekend. The Manitoba Crop Report first noted that producers were starting to plant soybeans as of its May 19 report.

Despite farmer anxiety due to seeding delays, Kaminski argued that growers may not have wanted to seed soybeans earlier than the third week of May, since it was only then that soils were sufficiently warm.

Daytime highs broke 20 C for the first time as of the May long weekend. The following week saw several days with wind gusts over 50 kilometres an hour, which promised to dry fields.

While soybeans will likely have been treated with fungicide, Kaminski stressed the need for crops to go into warm, packed soils and emerge promptly while seed treatment is still effective.

Yield data from Manitoba Agricultural Services Corporation from 2005-13 does suggest that soybeans drop below full yield potential if seeded later than the third week of May, although yield potential remains higher than crops such as cereals.

Cassandra Tkachuk, production specialist with the Manitoba Pulse and Soybean Growers, has also tagged this spring for its root rot risk.

“I’m hoping that this warm weather turns it around,” she said May 20, but warned producers who planted earlier-season pulses like peas or fababeans to keep a close watch for disease.

Disease monitoring out of Agriculture and Agri-Food Canada last year found some evidence of rot in every field sampled, despite a dry year. Researchers found no evidence of pythium in any of the soybean crops sampled, a report published in the Manitoba Pulse and Soybean Growers Pulse Beat said, but fusarium was found in all 40 analyzed fields. Rhizoctonia and phytophthora were also found less commonly.

Fusarium, likewise, was the biggest culprit of root rot in field peas last year. The monitoring found fusarium root rot in 98 per cent of fields analyzed, although average severity hovered around 2.9 out of a scale of nine.

“Eventually, no matter what disease is kind of lurking there, fusarium eventually kind of takes over, so that could be part of the result that we’re seeing, but if there’s a year to see pythium, then this probably would be the year,” Tkachuk said.

Materials from the Manitoba Pulse and Soybean Growers warn that crops seeded into wet, cold soils, like those reported province-wide this year, have greater risk of stress from pythium, while wet and warm soils are friendly to both rhizoctonia and fusarium.

Kaminski, however, argued that the idea of pythium as a cold-soil disease is a misconception.

“Pythium does not necessarily like it cold,” he said. “Pythium is a water-loving fungus and it has its advantage whenever soil is near saturated and attacks the fine feeder roots. It may be having an impact, but as far as temperature requirements go, that’s neither here nor there.”

Temperature does, however, impact how much a crop suffers from root rots, he said.

In the end, exact species might not matter as much as whether there is seedling disease present in general, Tkachuk said. The production specialist noted that many of the root rots impacting pulse seedlings are impossible to differentiate visually.

There is also little the producer can do this year, if they did not already opt for seed treatment. With the exception of phytophthora, which can infect a soybean plant at any stage of growth, the most common root rots will all infect plants in the early season, Tkachuk said.

A root rot problem this year, however, can inform decisions next year when producers are pondering whether to spend the extra money on seed treatment or re-evaluating their rotations, she noted.

About the author

Reporter

Alexis Stockford

Alexis Stockford is a journalist and photographer with the Manitoba Co-operator. She previously reported with the Morden Times and was news editor of  campus newspaper, The Omega, at Thompson Rivers University in Kamloops, BC. She grew up on a mixed farm near Miami, Man.

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