Pea, canola growers advised to scout fields for disease

ST. ALBERT, Alberta — When crop disease specialist Robyne Bowness stood in front of a perfect pea crop to discuss pea crop disease, she was a little embarrassed.

She looked at all the plots, searching for signs of disease to show those attending the crop walk at the University of Alberta farm north of Edmonton, but found none.

“These plots are completely disease free,” said Bowness, an Alberta Agriculture crop disease specialist.

The plots may not stay that way. A recent hailstorm left white marks on the pea pods.

A weakened plant is more susceptible to disease and Bowness predicts the combination of moist, warm weather and weakened plants will be an invitation for disease.

“Now that hail has hit, the disease will move in and it will move in quick,” said Bowness.

While these plots were disease free, there are three main diseases affecting peas.

Ascochyta complex is three pathogens working together. As the first disease to show up in the crop, it starts at the bottom of the plant and works up the canopy.

The disease is spread by rain and rain splashed spores. A dry season will stop ascochyta from spreading.

Recent hail on a healthy crop of peas at the University of Alberta research farm at St. Albert, Alberta, will make the crop more susceptible to disease. | Mary MacArthur photo

Rotation and fungicide are the only ways to control the disease. Bowness, who said timing of fungicide is critical, recommends scouting pea crops twice a week to catch the fast moving disease.

Downy mildew is a relatively new disease that causes a grey, fluffly mycelium or fuzz on the underside of leaves. The disease has shown up in the Vegreville and Vermilion areas.

The fungus hasn’t been a general problem, but it can be devastating in affected areas. Fungicides are effective. It doesn’t like heat and is usually gone by mid-July.

Sclerotinia or white mould attacks canola. With recent cool, wet weather, sclerotinia is starting to show up in pea crops and canola.

“It’s the same beast and will go back and forth between the two crops easily,” she said.

Sclerotinia causes a white bleaching of the stem and a white cottony mould grows on the stem and pods. It’s not a huge economic disease in peas, but will likely become a more serious problem as acres increase, she said.

Bowness recommends growing canola after peas because there are more fungicides registered for sclerotinia control in canola.

Crop rotation and fungicide are the farmers’ main tools to fight the disease.

Bowness predicts fusarium root rot will soon become one of the pea producers’ biggest disease problems.

“So far, there have not been devastating effects, unless you are one of the ones who has had it on your farm and it has completely taken your crop down,” she said.

The pea crops can look good, then go down for no obvious reason after flowering.

The bright pink or red colour inside the root easily identifies fusarium.

“Once it’s on the farm and you start spreading it around, it lives for a very long time. Watch out.”

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