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Out of the box thinking may provide tools to successfully manage diseases such as Aphanomyces root rot. GROW YIELD 23 | Pulse Research Report PROJECT TITLE Cover crops as part of a rotation strategy to reduce pea root rot, and evaluation of other management options PROJECT LEAD Syama Chatterton, Agriculture and Agri-Food Canada TOTAL VALUE OF PROJECT $1,456,100 For many diseases, in many crops, fungicide application can be an effective and economical way to manage disease and maintain crop yield and quality. Despite the widespread use of fungicides, not all diseases have this defensive toolkit available. Aphanomyces root rot is one of the glaring exceptions. "Aphanomyces produces long-lived resting spores that affect legume and pulse crops such as peas and lentils," said Syama Chatterton, Lethbridge-based Plant Pathologist with Agriculture and Agri-Food Canada. "It can be managed by crop rotation, but it's an extremely long one. You might have to wait six to eight years between pulse crops." Given these crops' economic and agronomic advantages, having peas and lentils in the penalty box that long is far from ideal. Short of new fungicide products, is there another way to bring peas and lentils back into the fold sooner? There could be. As Chatterton explains, research has shown that Brassica crops release chemicals that act as a biofumigant. In concept, a green manure Brassica cover crop could reduce the Aphanomyces spore count and thus accelerate the grower's ability to grow peas and lentils. This is ground-breaking research. Aphanomyces, as a causal agent of root rot, was only discovered to be prevalent in Alberta in 2012. Seed treatments have not been found to be a comprehensive solution. By giving growers a potential option to rehabilitate fields compromised by Aphanomyces, Chatterton is helping to maintain the role of peas and lentils in a balanced crop rotation. FALL-SEEDED MUSTARD AS A GREEN MANURE CROP In 2017, with funding from Alberta Pulse Growers, Chatterton began a four-year study into the effectiveness of the Brassica cover crop strategy. "There's a lot of greenhouse research that shows a Brassica green manure crop, mixed into soils, breaks down Aphanomyces resting spores," she said, "but this research has not yet been done in the field. We are using fall-seeded mustard, because it's believed that mustard has the highest biofumigant ability, along with tillage radish." The field where Chatterton is conducting this research last grew peas in 2014. Judging by its level of Aphanomyces spores, this field should be out of peas for several more years. Chatterton will assess whether the field's Aphanomyces spore count can be brought back down to a range that's viable for peas and lentils, and how quickly. She'll assess how the spore population changes from year to year and how well this strategy would work in a no-till system. "This is a long trial because we need a longer period of research to look at this issue," Chatterton said. "By the time we're three or four years out and look at the inoculum in the soil, will it still be too high to plant peas? That's what we want to find out." Brassica cover crops such as mustard could reduce the volume of Aphanomyces spores in the soil. A new research project is investigating. Getting Peas and Lentils Back in the Rotation

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