Maine foresters vigilant for oak disease

PORTLAND – It sounds like something out of a horror movie.

But concerned scientists are saying sudden oak death, a fungal disease that already has killed thousands of oak trees in California, could spread to Eastern states including Maine and devastate existing forests.

The U.S. Department of Agriculture announced last month a plan to devote $15.5 million to battling sudden oak death, which potentially could infect Maine’s commercially valuable northern red oak. Maine foresters and horticulturists have begun conducting forest surveys and screening plants in local nurseries as part of a nationwide effort to determine how far the disease has spread.

“Since a lot of nursery stock is grown in Oregon and California and shipped all over the United States, we have to be concerned with material coming in that is a possible host,” said Clark Granger of the Maine Forest Service’s forest health and monitoring division.

Sudden oak death was believed to be confined to California and Oregon until more than 100 nurseries in 13 states received infected plants from a single nursery in Southern California.

None of those plants came to Maine, but 28 potted bonsai camellias from a California mail order nursery that had infected plants were shipped here last November and December, state officials said.

Though there is some question whether sudden oak death could survive Maine’s tough winters, one leading scientist working on the problem said it’s important not to underestimate the disease.

“I definitely wouldn’t pin any hopes on the fact that the frost is going to kill it,” said Brett Tyler, a researcher at the Virginia Bioinformatics Institute in Blacksburg, Va.

Tyler said scientists don’t yet fully understand how sudden oak death spreads, but it seems to have “a broad appetite” for woody shrubs, which serve as hosts for the disease. Sudden oak death doesn’t kill the shrubs but infects a few of the leaves and produces a large number of spores. Those spores get onto the oak tree and make their way under the bark, where the disease cuts off the tree’s food supply.

Once symptoms start to appear, it’s too late to save the tree. And once it gets into a forest, Tyler said, it’s extremely difficult to control, and so containment is considered the best control strategy.

Maine is participating in the national survey of nurseries.