Berry growers assess tough new fungus

Posted July 29, 2009, at 11:27 p.m.
David Kilton of Machias carefully examines blueberry leaves infected with Valdensinia leaf spot, a fungus that is spreading in Maine's blueberry fields. The fungus does not affect the blueberry crop but defoliates the bushes and unless burned, will spread more widely next year. More than 50 blueberry farmers gathered Wednesday night at Blueberry Hill Research Center in Jonesboro to learn how to identify and eradicate the fungus, which has been found in six fields in Maine so far. (Bangor Daily News/Sharon Keily Mack)
David Kilton of Machias carefully examines blueberry leaves infected with Valdensinia leaf spot, a fungus that is spreading in Maine's blueberry fields. The fungus does not affect the blueberry crop but defoliates the bushes and unless burned, will spread more widely next year. More than 50 blueberry farmers gathered Wednesday night at Blueberry Hill Research Center in Jonesboro to learn how to identify and eradicate the fungus, which has been found in six fields in Maine so far. (Bangor Daily News/Sharon Keily Mack)

JONESBORO, Maine — As blueberry growers filed out of a meeting at the University of Maine research center Wednesday night, one muttered under his breath, “This is going to be a nightmare.”

He was talking about Valdensinia leaf spot, a fungus just now being found in Maine’s blueberry fields, and the steps growers must take to eradicate it.

“If you see it, get rid of it,” Dr. Seanna Annis, a plant pathologist at the University of Maine, told more than 50 growers at the meeting. “Be vigilant. You may have to give up that area to save the rest of the field.”

But Annis was adamant about the integrity of this year’s harvest, which begins in just about a week.

“The blueberry crop is not doomed,” she said. “The crop this year is perfectly fine. The fungus doesn’t affect the blueberries at all.”

Growers had lots of questions for Annis, who has now found the fungus in six fields in Washington and Hancock counties.

They wanted to know how to treat the fields, how to prevent it from spreading, how to identify the fungus and how it got to Maine in the first place.

They also wanted to know why no one from Wyman’s or Cherryfield Foods, the two largest wild blueberry producers, was at the meeting.

Annis explained that she had visited both companies in the past two days and they are taking precautions in their fields.

Annis, who said the fungus has been rampant in Nova Scotia and has now spread to Quebec, New Brunswick and Prince Edward Island, said one possible culprit was the harvesting machinery, rakers and blueberry boxes that move back and forth between U.S. fields and Canadian fields.

“But the bottom line is, I don’t know,” she said. “I think it came in last fall during the harvest and spread from one single spot.”

She is sure, however, that VLS spreads quickly and kills what it infects. She suggested burning all areas of infection to stop the spread to healthy plants.

Using slides, Annis described VLS as large, bull’s-eyelike spots on the leaves. “We have not seen this in Maine before,” she said. Once a spot appears, the green leaves drop under the bushes, where they produce more spores and reinfect the plants. “This fungus can survive in the vein of dead leaves up to two years,” Annis said.

In the spring, after three days of rain or wet conditions, the spores will produce and reinfect again.

“We’ve seen other leaf spots,” she said, “but this one is particularly worrisome.” She acknowledged that burning the blueberry bushes while the leaves are green could cause the loss of some plants.

But don’t burn fields willy-nilly, she said. “Confirm that you have this first. Then hard-burn the infected area now and later burn the whole field as usual.”

She advised not to use mechanical burners but instead hand-held burners. “Do it now instead of waiting,” she said.

She said there is a single fungicide, Pristine, which can slow VLS down but will not eradicate it, and it costs $65 an acre to apply. Because the fungus has been in Nova Scotia for years, scientists there are close to finding a fungicide that kills VLS. “It is in trial right now,” Annis said. “It could be released soon.”

One farmer, with hundreds of acres to harvest, said, “I can see this is impossible, whether you are using a harvester or rakers. You’re gonna spread it.”

Annis said producers need to clean their harvesters before moving to another field, disinfect vehicle tires and footwear, and make sure blueberry boxes and rakes do not have any leaves on them before moving to a new location. “Check when your harvester shows up,” she said. “I’m sure we can all cope with this.”

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