Late blight fungus ruining tomato and potato crops

While the cool, wet summer weather might come as a relief to some who struggle through the heat, farmers in parts of Southern Ontario are feeling its affects, particularly on tomato crops.

A fungus called late blight has ruined a number of commercial crops, particularly the organic variety.

Other parts of Canada are dealing with the destructive disease, which isn’t harmful to humans. The federal government issued an alert in Prince Edward Island, advising farmers to adopt PLANT-Plus system, a prediction system, to help farmers “with the implementation of reduced risk management strategies on their farm.”

In British Columbia, the ministry of agriculture has a comprehensive breakdown of the fungus on its website, from its symptoms to tips on late blight management.

Monica Brandner, a farmer with Brandner Farms in Ruthven, Ont., says since she grows tomatoes organically, it’s been particularly hard. The fungus has affected up to 80 per cent of her tomato crops.

“For us, it’s a bit more challenging because we don’t spray with chemicals to take care of funguses, so sometimes it knocks the crops out for us,” she tells Yahoo Canada News.

While Brandner was able to get the first couple of picks off the tomato plant, the fungus killed any further growth. She says the damage doesn’t affect the price of her product, which she sells on her farm and at Windsor’s city market year round.

Janice LeBoeuf is the vegetable crop specialist with the Ontario ministry of agriculture, food and rural affairs. She says farmers who don’t work organically can use crop protectant to stop the spread of the fungus, though backyard gardeners will prove to have more challenges.

“There isn’t too much in the way of cultural management practices that could prevent late blights, so it can be a big problem in gardens,” she says. “If you find it early, you can take the plant and bury them or seal them in plastic garbage bags because the legions on those plants can produce spores that can affect other plants.”

The fast acting disease caused by Phytophthora infestans can kill potato and tomato plants within days, if the weather is conducive. The fungus thrives in wet conditions, like dew or fog, as well as in the lower temperatures. Heat, on the other hand, slows it down.

The fungus manifests as a black legion on the leaf of the plant and spreads to other parts, like the stems and fruit, which appear bruised and lumpy. Eventually the plant will rot.

Overall, LeBoeuf says late blight affected about two to four per cent of processing tomato crops in Ontario.

Brandner says that’s the reality of being a farmer.

“There’s usually one vegetable every year that doesn’t like what Mother Nature brings it,” she says. “Last year it was trouble with tomatoes again. You don’t have a choice, there’s no way of changing it. You have to work with it.”