Late blight plagues Chittenden County (8/6/09)

Williston growers on the lookout

Aug. 6, 2009

By Tim Simard

Observer staff

Farmers and growers across Vermont fear the worst as the fungal disease known as late blight strikes gardens and farms. Vermont agricultural officials have confirmed the disease in every county in the state, and it’s becoming more and more prevalent in Chittenden County.


    Courtesy photo
The leaf of a tomato plant shows the signs of late blight, which has infected tomato and potato crops in Vermont.

But some growers in Williston have so far escaped the fungal infection, which destroys only tomato and potato crops. It is not harmful to people.

Lisa Boutin, co-owner of the Boutin Family Farm on South Road, has checked her tomatoes and potatoes daily. She said there have been no signs of late blight, which appears as black, irregular spots on leaves and stems. In advanced stages, the blight will rot and discolor tomatoes and potatoes.

“So far, everything is looking good,” Boutin said. “We start our own (tomato) plants indoors, so I don’t know if that makes a difference.”

Boutin said the tomatoes are coming along fine and should be ready shortly for her community-supported agriculture customers. Boutin Family Farm is a CSA, where individuals buy shares early in the growing season and receive fresh vegetables for the rest of the summer and fall.

Boutin said she planted a row of potatoes for her family and those plants are also currently free of late blight. She’s hoping it stays that way. The Boutins routinely spray their plants with an anti-fungal spray in an effort to curb fungal plant diseases that become common during wet and cool summers.

She knows late blight could appear on her farm overnight. Once late blight appears, it rapidly kills the plants.

“I’m checking (the plants) every day,” Boutin said.

Spread of late blight

This summer has been anything but average in Vermont. The state experienced near record high rainfall totals in June and July, with temperatures averaging well below normal. Only in the last few days of July did the temperature climb to normal levels in the 80s. But the rains continued. Last week, northern Vermont was again slammed with torrential rain and thunderstorms for several days.

The consistently wet weather pattern is the perfect breeding ground for late blight, explained Ann Hazelrigg, a University of Vermont professor and director of the university’s Plant Diagnostic Clinic.

“I haven’t seen it this bad in 25 years,” said Hazelrigg, who is also a Williston resident.

Late blight, also known as Phytophthora infestans, is the same disease that caused the Irish potato famine in the 1840s. Hazelrigg said this summer’s weather is similar to what Ireland experienced during that time period.

“With these rains, (late blight) sort of just washes out of the sky,” she said.

Late blight is an airborne disease that travels through fungal spores. Gardens that have not been infected are lucky, Hazelrigg said. She said farms throughout much of the Champlain Valley haven’t been so fortunate, including the Intervale in Burlington.

Master Gardener June Jones said the Williston Community Garden in Brennan Woods has been lucky so far. The tomato plants at the garden have only dealt with an early blight, which is not nearly as destructive. Jones said the gardeners have sprayed fungicide and weeded the plants to prevent the spread of early blight. So far, they’ve been successful.

“We did have some of the late blight last season,” Jones said. “When (the plant) gets it, that’s it.”

Hazelrigg said once a plant is discovered to have late blight, it must be completely removed from the garden. Growers should not compost the plant material, but should instead throw out the plants. Larger farms may choose to burn the plant material.

While tomato plants afflicted with the fungal disease are a lost cause, some potato crops might survive. Hazelrigg said potato plants with the disease should be removed, but potatoes can survive and harden in the ground after the plants’ removal. She said growers should check the potatoes once they’ve been harvested to make sure they’ve escaped the disease.

Hazelrigg said the good news is that late blight does not last within the soil over the winter. Growers should feel safe replanting the same ground next year.

The bad news is the cost of the blight to farmers. While Hazelrigg did not have an estimate on the economic impact of late blight, she said it could prove devastating for some.

“Organic farmers, especially, could be in big trouble this year,” Hazelrigg said.

At this point, only hot and dry weather can stop the spread of late blight, Hazelrigg said. But forecasters aren’t calling for any extended dry spells. There could be light showers over the weekend and into early next week, with temperatures in the 70s and 80s.