Researching root rot control in peas

Evaluating the benefits of seed treatments, soil amendments and soil tests

There’s still a lot to learn when it comes to managing root rot, especially aphanomyces. When are seed treatments most effective? Do soil amendments help? And can soil testing help farmers pick the best pea fields?

Fortunately, research is underway to answer those very questions.

Dr. Syama Chatterton, an Agriculture and Agri-Food Canada (AAFC) researcher based in Lethbridge, is collaborating on two projects that promise to shine light on management practices around aphanomyces and fusarium.

Researchers on the first project are studying how seed treatments and soil amendments affect disease and yield in fields infested with aphanomyces and fusarium root rot. They’re also screening pea varieties to see how they fare when exposed to aphanomyces.

Chatterton’s collaborators include Dr. Mike Harding and Robyne Bowness with Alberta Agriculture and Forestry, plus Dr. Bruce Gossen, with AAFC in Saskatoon. Together, they’re running trials at seven Alberta sites and one near Saskatoon. All the sites, except the one at Lethbridge, are in farmers’ fields. The sites have high aphanomyces levels, distributed uniformly over the field. Only the Lethbridge research centre site has fusarium root rot.

Confidentiality agreements prevent Chatterton from specifying all the seed treatments being studied. But Intego Solo, registered for aphanomyces, is one of them.

“Basically we’re look at seed treatments that had active ingredients against the whole root rot complex. So that’s fusarium, pythium, rhizoctonia and aphanomyces,” said Chatterton.

Researchers are also looking at soil amendments reported to work against aphanomyces. That includes lime, along with Phostrol (a phosphorus acid used as a fungicide) and the herbicide Edge (a Group 3 herbicide with active ingredient ethalfluralin).

Pea varieties being screened include about 20 commonly grown cultivars that are already registered. Chatterton said because aphanomyces is new to Alberta and Saskatchewan, these cultivars hadn’t been screened before.

To measure the early effects of treatments, particularly seed treatments, Chatterton and her colleagues rate disease severity a few weeks after seeding. A second rating at flowering or early podding evaluates the treatments when the disease is most severe. They also take NDVI measurements throughout the growing season to measure the treatments’ effects on shoot health. Finally, they assess yield in thousand seed weight.

Early season results encouraging

Chatterton said the early season results from the seed treatments and soil amendments were encouraging. Visually, the roots from some treatments looked much healthier than others.

But by the growing season’s end, root rot severity was the same across all treatments, she said. Some treatments saw improved yields, but those improvements weren’t statistically significant, Chatterton said.

Chatterton cautioned that it’s only the first year of a three-year study, and so it’s too early to make recommendations.

“Because 2015 was such an unusual year as well, these unusual environmental conditions can sometimes affect what the results are,” she added. For example, they had a site near Drumheller that was so dry, they weren’t able to take the trial to yield. She hopes to share results after the second year of the trial.

Chatterton said she’d like to continue the study beyond three years to see whether different management practices work better as the inoculum levels drop. The current trials are funded by the Alberta Crop Industry Development Fund, the Alberta Pulse Growers, and Agriculture and Agri-Food Canada.

Soil testing 
for aphanomyces

Chatterton and Dr. Sabine Banniza from the University of Saskatchewan are also developing a soil test for producers struggling with aphanomyces.

Chatterton said the soil testing project is piggybacking on the other management trials. The study looks at not only how much inoculum is in the fields, but also “at what level of inoculum will each of these management strategies be effective,” she said.

The project will address practical questions, such as how many samples farmers would have to collect to gauge aphanomyces risk in a given field. Chatterton said they’ve started collecting from areas known to be infested with aphanomyces, plus low-lying areas prone to water saturation. They then move out sequentially from those areas to see how far out producers would have to go.

2015 marked the first year of the three-year project, funded by the Saskatchewan Pulse Growers. Chatterton hopes to share results by the end of the third year.

“And again, we’re looking at three different soil zones because early results are suggesting there might be differences in inoculum potential in different soil zones.”

About the author

Field Editor

Lisa Guenther is field editor for Grainews based at Livelong, Sask. You can follow her on Twitter @LtoG.

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