By Alice McFarlane

Wet weather and humidity increase sclerotinia risk

Jul 15, 2020 | 12:33 PM

MELFORT, Sask. – Does your canola crop need protection from sclerotinia stem rot?

There is a history of sclerotinia on the prairies so the potential for disease is always there as long as there is moisture.

The disease needs moist soil to get the sclerotia germinating to form the mushroom like apothecia that release the spores.

A petal and spore test can help with the decision to spray a fungicide. Canola Council of Canada agronomy director Clint Jurke said testing removes half of the decision-making process.

“Is there enough moisture up to flowering to produce the inoculum?” Jurke said. “It really comes down to if you have the inoculum are conditions conducive for the development of the disease.”

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A field will need about five to 10 millimetres, more then two days a week and a daily minimum relative humidity over 80 per cent to fire up the stem rot infection cycle.

Agriculture and Agri-Food Canada research scientist Kelly Turkington said the wet pants test is a practical way to address the issue.

“If you go into the crop in the morning, the soil surface is dry, the canopy is dry, your boots aren’t muddy and your pants aren’t wet the risk in terms of the environment component is probably quite low,” Turkington said.

If your pants get wet while scouting canola mid day the canopy has enough moisture for the development of the disease.

If you have decided to apply a fungicide the next step is to determine the right time to do this.

Agriculture and Agri-Food Canada research scientist Dwayne Hegedus said timing is critical and an application at 20 to 30 per cent flower provides the greatest benefit.

“The important thing is to spray early because within hours the plant tissues become infected. Within 12 to 24 hours the fungus is already beginning to move through the plant and within 24 hours you can see very visible signs of necrosis,” Hegedus said.

Once the petals become infected and there is contact with the plant surface, Hegedus said your window to apply a fungicide has narrowed.

Farmers have access to several tools for spore testing. Spornado from 20/20 Seed Labs or DNA based pedal testing kits from Quantum Genetics and Discovery Seed Labs can be helpful.

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alice.mcfarlane@jpbg.ca

On Twitter: @AliceMcF