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It starts as nickel-sized water spots on the undersides of leaves. It can spread throughout the entire plant in only a couple of days. It can cause large brown areas to develop on the fruit. It’s late tomato blight in the Mad River Valley.
Late tomato blight is a fungal disease that spreads via wind-borne spores, affecting some gardens and skipping others. Many tomato-growers in The Valley were hit with the blight at the end of last summer and—unfortunately for some—it’s back.
Already, the blight has affected tomatoes in multiple plots at the East Warren Community Gardens and at the top of Brook Road in Warren, and gardeners in Waitsfield and Fayston have found the same tell-tale spots in their own backyard plots.
Aaron Locker, a grower at Kingsbury Market Garden on Route 100 in Warren, has not seen signs of the blight in his tomato crop this year—“at least not yet,” he said. “My guess is that the dry summer helped,” Locker explained, as the spores need moisture to take hold, but high amounts of upcoming rain could change his luck.
“I think it’s important for folks to know how to properly deal with [the blight] in order to keep it from spreading,” Locker said, as “just one home gardener who does not deal with it properly can affect an entire town the next year.”
According to an advisory article published by the University of Vermont (UVM), gardeners should be watching their plants daily for signs of the disease, and they should act quickly to destroy all affected plants at the first sign of spots in order to limit the spread of spores to other areas.
Since late blight needs living plant tissue to survive, gardeners can stop the spread by cutting their plants and putting them in trash bags to send to the landfill—not in a compost, where the spores can still flourish—and for larger crops, farmers can properly dispose of their plants by cutting and burning them. If only the leaves of a plant have been affected, growers can safely salvage and eat the fruit, but they shouldn’t can it.
“Last year, almost all of my heirlooms and larger tomatoes got late blight,” director of the Mad River Localvores Lisa Barnes said, noting that some varieties of tomatoes—such as heirlooms—are more vulnerable to the blight than others. “This year, I only planted cherry tomatoes, and I cut most non-flowering stems to increase airflow and had no problems with it at all,” Barnes said.
Other preventive measures gardeners can take to avoid late blight involve the use of fungicides. According to UVM, garden fungicides labeled for tomato use that contain the active ingredient chlorothalonil—or copper fungicides, for organic growers—can protect crops from the incriminating spores, but they are only effective if applied five to seven days before the disease appears, and they must be regularly re-applied during wet conditions.
So, in the final weeks of harvesting, as those already affected by the blight take the time to properly dispose of their plants, maybe those more fortunate can help thank them for helping to contain the disease by tossing them a tomato or two.