Eric Schick’s first encounter with Aphanomyces root rot in lentils was in 2012, an unusual year for fields south of Moose Jaw.
“2011 was really wet, followed by a lot of snow, then we came into a wet spring where it just didn’t stop raining,” he said.
Soon, the lentil crop developed patches of yellowing, stunted plants. A look underground revealed nearly nonexistent roots coated with a caramel-coloured layer and no nodule development.
Schick was speaking at the Crop Production Show in Saskatoon this January. An independent agronomist before joining Nufarm, his family farm grows durum, barley and lentils in rotation and also raises cattle south of Moose Jaw. He said the area is a hot spot for root rot and for years producers around Assiniboia had to abandon lentils.
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“So we’re trying to figure out, what do we have to do to get these acres back and keep them in a pulse?” Schick said. “Lentils have built many farms in this province and I want them to succeed into the future because I plan on making a living off of that too.”
Aphanomyces is a water mould and its spores can persist in the soil for more than 10 years. When the right moisture conditions arrive, the spores wake up. Long, thread-like hyphae grow, invading nearby roots and parasitizing them for nourishment.
“This is where you see necrosis in the plant and you’re going to see both above-ground and below-ground death,” Schick said.
To illustrate how the spores are unavoidably spread by farm implements, Schick showed photos of an Aphanomyces outbreak in a field where yellowed, dying lentil plants appeared as streaks that followed the same tracks as the seeder.
“This field at the end of the year ended up yielding 28 bushels,” he said. “For a large green lentil field that’s awesome, but what could it have done without this Aphanomyces?”
While Aphanomyces prevalence varies across the province — Schick cited a hot spot around Rosetown — the mould seems to be everywhere.
“The worst thing about this picture is that there is no field with zero,” he said.
It takes about Aphanomyces 100 spores per gram of soil to see symptoms in a lentil or pea crop. Yield loss shows up at the 400-500 spores-per-gram level. There’s no way other than time to reduce this disease pressure.
As an example, Schick said if a soil is testing at 1,000 spores per gram, it will take five to six years to bring it back down to the 100 spores-per-gram symptom threshold level.
“And if we keep on populating these soils, say up to 10,000 spores on a test, in 10 years, you’re still going to be seeing symptoms,” he said. “So how can we alleviate this problem?”
Schick advocates for a strategy of knowledge, prevention and, when necessary, treatment.
The knowledge part comes through testing, either of plant material or soil. It’s hard or impossible to tell by looking whether an infection is caused by Aphanomyces or Fusarium, or a combination of several pathogens. Factors such as poor nutrient levels can weaken plants and make them more susceptible to disease as well.
“Whenever it’s in question, get it tested,” he said.
Laboratories can give simple yes or no results as to whether a disease is present, or more sophisticated answers that tell how many spores of a pathogen are in a gram of soil.
Schick also urges producers to resist the temptation to cut corners on seed treatments.
“Coming from the retail side, I’ve heard the comment, ‘I’m going to seed into the cold, wet soil early. Nothing’s active, I’m going to plant those peas deep, they’re not going to come up for a while. There’s no disease there.’ Well, cool, wet — Pythium has a chance to take over,” he said.
Dry and hot is also offers no protection. Schick said some producers will skip seed treatments late in the seeding season.
“There’s Rhizoctonia just waiting, ready to take over this guy’s dry seed. I come from chickpea country and you’d never believe, looking at dry root rot, how a plant could die when you haven’t had rain in three months.”
While there are many seed treatments out there, Schick highlighted Nufarm’s product, Zeltera Pulse. Registered for use on all pulses in Saskatchewan, the product features four active ingredients for control against all major diseases in Western Canada.
Two of the product’s four modes of action target every labelled class of pulse disease to manage resistance, as well as protect against Aphanomyces and Fusarium root rot. It contains the Group 4 fungicide metalaxyl, Group 7 fungicide inpyrfluxam, Group 11 fungicide mandestrobin, and the Group 22 fungicide ethaboxam.
The company rolled out Zeltara Pulse in 2022, but supply chain issues limited availability. They did work with a farmer to carry out trials around Ponoka, Alta.
Schick said that with plentiful rain — about 280 millimetres during the growing season — the Zeltara-treated trial yielded 40 bu. per acre. In contrast, the farmer’s usual treatment produced a crop so riddled with volunteer canola that it was cut for silage.
A final control, on land that hadn’t seen peas for eight years, gave a window into what a disease-free field would look like. It yielded 70 bu. per acre.
“No inoculum; big yields. I wish we all had that kind of ground,” Schick said.
For everyone else, management remains a priority to monitor and keep spore counts down. Rotations are part of this as well as vigilance in the form of testing.
“I think we need to move to testing our soils and planning for oospores to see what kind of load we’re dealing with when looking at these rotations,” Schick said. “Once again, the challenge I have for you is, can we proactively delay this with a seed treatment and still continuously be able to grow pulses?”
