March 10, 2010

Fungus poses threat to Maine's low-bush blueberry crop


— By

Staff Writer

Due to the wet summer, the wild blueberry harvest is running about a week late this year. But growers are still hoping for a bumper crop, if they can keep a new threat to their fields under control.

Valdensinia leaf spot is a very small fungus that could cause very big problems for Maine's low-bush blueberry industry.

''We've made a major effort to do an educational push on this, because this is something very different than (growers) have dealt with in the past,'' said David Yarborough, a cooperative extension blueberry specialist and professor of horticulture at the University of Maine. ''Up in Nova Scotia, the disease has been there a few years, and those people who ignored it are now paying the price.''

''Paying the price'' means burning entire fields and watching all those plump, ripe berries -- and profits -- go up in smoke.

Valdensinia leaf spot attacks the leaves on low-bush blueberry plants, covering them in brown spots. Eventually, the diseased leaves fall off, and the infected stems won't grow flower buds.

The fungus does not harm the fruit itself, but infected fields must be burned to prevent the disease from spreading.

The fungus thrives in wet weather, which Maine has had plenty of this summer. It can be spread from field to field on harvesting equipment or even on shoes. Just one wet, infected leaf stuck to the bottom of a boot could destroy an entire field.

Experts are telling growers to steam-clean all their equipment before moving it between fields and to clean blueberry boxes before they are taken into the fields.

Yarborough said Maine growers are being advised to burn small areas of their fields where the disease shows up.

''If they can burn out little areas of the fields overall, it's not going to be a huge impact,'' he said, ''but if they ignore it and allow it to infect the whole field the next year, they'll have no berries.''

The fungus is not likely to affect cultivated blueberry fields because they typically are not grown in the same areas as wild blueberries, Yarborough said.

''Also, it doesn't seem to be as bad a disease in the cultivated (blueberries) just because of the structure of the plant,'' he said.

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