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With the recent find of a new phytoplasma disease north of the Washington State-Canada border, grape growers should be extra vigilant of what’s happening in their vineyards, said Dr. Ken Eastwell, Washington State University pathologist.

Bois noir, known generally as grapevine yellows, and the related disease Flavescence dorée, have caused major problems in Europe, Eastwell said. He participated in an investigation of grapevine yellows last summer in British Columbia, at the invitation of the Canadian Food Inspection Agency.

An unknown

"It’s a big concern here because it’s a new pathogen in a new environment," he said. "We don’t have the major vector known to transmit the disease here [in Washington], and we just don’t know how the disease will behave."

In the last five years, scientists in Europe and North America have noticed that leafhoppers have moved about five degrees latitude north, he explained. The disease spread with the leafhoppers and may have compromised grape certification programs in Europe.

"Of all the time I’ve been involved in quarantines in North America, these two yellows diseases are the two that we wanted to keep out," Eastwell said. "That’s why it’s so important to follow quarantine regulations when bringing in grape material and to plant clean stock."

Eastwell encouraged Washington grape growers to be aware of changes in their vineyard and to contact Dr. Mercy Olmstead, WSU viticulture Extension specialist, if they see vines that look suspicious.