Pulse School: Assessing In-Field Tools for Managing Aphanomyces (Do I Have to Wait Six Years?)

Root rot damage. Photo Credit: Syama Chatterton

Taking a break from peas or lentils for six years is a tall order for fields where aphanomyces has been a problem. Are there in-field options or tools for managing this relatively new disease?

Syama Chatterton, pulse crops pathologist with Agriculture and Agri-Food Canada in Lethbridge, has been conducting field trials across the prairies over the last two years, looking at how aphanomyces levels vary with different varieties, seed treatment, and soil amendments.

When it comes to cultivar effect, she says they found no noticeable difference in the susceptibility between common varieties.

“We did maybe see some cultivars can still yield well despite an aphanomyces infection, so that will be data we’ll be releasing to producers to make decisions on which cultivars to grow,” she notes.

As for seed treatment, ethaboxam is the only registered product on the market. It’s labeled for early season suppression of aphanomyces in peas and lentils (as well as chickpeas and dry beans), and can be a good option for growers dealing with low to moderate infestations, notes Chatterton.

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“We did see that we got some of that early season suppression. When we evaluated roots at about five weeks after seeding, they did have less disease severity, but unfortunately we don’t always see that it carries forward long-term into the growing season,” she explains.

Lastly, they’ve also been looking at “anything noted in the literature, or even having anecdotal evidence that it might have efficacy,” explains Chatterton. That includes the following treatments:

  • foliar application of phosphite fungicide — Phostrol moves down to the roots and has shown efficacy against water mould pathogens, but isn’t registered on pulses in Canada;
  • liming — calcium can suppress the production of aphanomyces zoospores;
  • soil-applied trifluralin herbicide — has been noted in literature to be effective against aphanomyces;
  • growing brassica cover crops — green manure break-down could suppress oospores, but this could also increase disease risk for canola.

Further research is needed on all of these treatments, but Chatterton says, she hopes growers will eventually be able to test their soil for inoculum potential, and then make decisions based on the level of risk.

“It’s such a new disease. The research takes a long time to catch up with the problem. Only being two years in, we’ve found some really good early results, but now we need to start mixing it all together and coming up with those best management strategies,” says Chatterton.

Ultimately, some of these tools could be effective in fields that have a starting infection, she says, “but really a long rotation is going to be the key for management.”

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