New tool designed for late blight detection

Eugenia Banks displays one of the spore traps she used last year to detect late blight spores in Ontario potato-growing areas.  |  Jeffrey Carter photo

NIAGARA FALLS, Ont. — A late blight spore detection system tested in Ontario last year could prove useful in other potato-producing provinces.

Eugenia Banks, a consultant to the Ontario Potato Board, talked about the system at the Ontario Fruit and Vegetable Convention in Niagara Falls Feb. 22.

“The presence of just one spore means the disease is around. They’re a bit like cockroaches,” Banks said.

“The fields I selected had late blight before and they had hot spots. That’s where I put the spore traps.”

Banks said she installed the traps before crop emergence in windy, field-edge locations. They were checked twice a week and the samples sent immediately by courier to A&L Canada Laboratories in London, Ont.

Once a sample arrives, a quick test can be completed in four hours that is capable of detecting a single spore. Banks said A&L will send email alerts to growers immediately if the test results are positive.

The traps, available from Sporometrics in Toronto, cost about $1,500 each plus tax. They come with trap cassettes that cost $7.50 each. A PCR test costs $25.

“It does require a commitment to manage these traps. You have to be committed to changing the cassettes and sending them in,” Banks said. “Finding spores in a very hot and dry season, like we had last year, is an indication that the test could be a valuable tool.”

Late blight, formally known as phytophthora infestans, thrives under wet conditions and moderate temperatures from 10 to 26 C.

Banks cited the experience of one grower who routinely applies fungicides early, regardless of whether plants are showing signs of the disease. He’s never had a late blight issue in the past 25 years, she said.

Banks described late blight as a “community disease.” If it shows up in one location, it’s bound to spread, and so growers who have identified the problem should sound the alarm.

Vikram Bisht, a plant pathologist with Manitoba Agriculture, agreed. While late blight wasn’t an issue in Ontario in 2016, Vikram said it was widespread in Manitoba.

“This is a bad thing, not to talk about it if you have the problem,” he said.

Late blight often arrives in Canada on air currents from American growing areas.

Spores can survive on their own, but late blight requires living tissue, including solanaceous weeds such as hairy nightshade, in order to develop. It can also survive in potato cull piles, which should be destroyed, on potato plant volunteers and on tuber seed.

Look for clean seed, keeping in mind Canada’s regulatory standards, Banks said.

“The CFIA standard allows one percent of seed tubers to be infested with late blight. In an acre, that works out to around 150 infested tubers.”

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