Gardeners fend off late blight

ADDISON COUNTY — Tomato season has come and gone, but late blight — a fungal disease that infected many tomato and potato crops in Vermont this summer — is still on the minds of many gardeners this fall.
As farmers and gardeners put their plots to bed, they’re taking care to make sure the blight, credited with causing the Irish potato famine of the 1840s, won’t spread to next year’s crops.
At Lewis Creek Farm in Starksboro, owner Hank Bissell reported that both his tomatoes and potatoes were hit by the blight. He was able to sell very few tomatoes, and anywhere from half to three-quarters of his potato crop was killed by the blight.
“It stops the potatoes in their tracks,” Bissell said. A few of the earlier varieties of potatoes survived, but the later ones were wiped out. “It knocked them out before they’d done much of anything.”
That meant Lewis Creek Farm had far less product to sell this year. The blight didn’t affect the farm’s “community-supported agriculture” (CSA) program much, because the CSA makes up such a small part of Bissell’s business, but it did cut into wholesale revenues.
Of course, Bissell pointed out that though many tomato crops were hit by the blight locally, no one went without tomatoes this year — a fact he thinks sheds some light on the current foods system.
“I’ve started calling this the New England tomato famine,” he said. “The irony is, however, that no one went without tomatoes, and certainly no one starved. That’s a comment on the incredible food system that we have that often gets a lot of disparaging remarks. We don’t go without here, even when there’s something as widespread as this blight.”
Farmers in the region took up the watch for late blight in July, after word got out that tomato plants sold at some large garden supply centers in the region may have been infected with late blight. The blight is caused by the fungus Phytophthora infestans, and according to vegetable and berry specialist Vern Grubinger at the University of Vermont Extension, the blight isn’t actually that uncommon in the Northeast, where cool summer temperatures and frequent rains help the blight thrive.
But typically the blight doesn’t crop up until later in the growing season, and it’s usually limited to a few farm fields or small regions.
This year, though, the blight showed up early and was more widespread than it had been in the past. The summer’s cool temperatures and wet weather created fertile ground for the fungus.
According to the Northeast Organic Farming Association of Vermont (NOFA Vermont), farmers throughout Vermont took estimated financial losses in the hundreds of thousands of dollars due to the loss of crops to the blight.
Now, as the growing season winds down, Bissell is taking care to make sure that the blight doesn’t “overwinter.” He’s not worried about the tomatoes: Any spores left on those plants will freeze and die over the next few months.
However, the disease could survive in potato tubers buried in the soil or insulated in the warmth of a compost pile.
“My biggest concern about next year is the potatoes,” Bissell said. “I just want to make sure that all of my potatoes are sold or dead by mid-March.”
If infected potatoes don’t freeze over the winter, they can produce spores when the potatoes sprout in the spring.
The good news, according to NOFA Vermont vegetable and fruit advisor Wendy Sue Harper, is that farmers and gardeners can take care to destroy infected potatoes. Harper recommends burying potatoes at least two feet deep; burning, freezing or chopping up potatoes before composting them; feeding the potatoes to livestock; or turning all dead blighted tomato and potato foliage into the soil to decompose.
If a gardener or farmer plants to compost diseased foliage during their garden clean-ups, they should use hot compost techniques to make sure all disease spores are killed. If a gardener uses cool compost methods or minimal management, they should let their compost pile sit for three years ore more before using it in their garden.
Harper also recommends gardeners check their compost piles in the spring and destroy any tubers that have sprouted. They also should check their seed potatoes carefully for signs of disease before doing any planting next spring.

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