Potatoes in Canada

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Late blight found in Ontario potato fields

August 8, 2023  By Potatoes in Canada

Late blight has been discovered in Alliston, Ont., potato fields and is causing substantial financial losses to impacted growers, as reported by Spud Smart. Late blight outbreaks have also been reported in Utopia and New Lowell, Ont.

There have been FTA cards sent to North Carolina State University to identify the strain. Eugenia Banks, a potato specialist with Ontario Ministry of Agriculture, Food and Rural Affairs, is hoping there will be more information available about the strain by the end of the week. Banks says the strain in the Alliston area is likely to be US 23.

“US 23 is very aggressive on tomatoes. Late blight spores have been reported from spore traps in tomato fields In Elgin and Essex Counies,” she says in the email to Spud Smart.


Banks is recommending growers use a tank mix of Kocide, Curzate and Ridomil to dry up the lesions. Spray intervals should also be shortened if there’s a lot of new growth.

“Late blight lesions are usually hard to find after the third spray, but that does not mean late blight has gone away. It’s just hiding and will come roaring back to life if conditions are right and no late blight specific fungicides have been applied,” Banks says.

She also notes Copper hydroxide kills late-blight spores and protects tubers. Kocide and Parasol have similar active ingredients, but Parasol is liquid and easier to handle.

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