Dutch elm disease claiming trees
November 24, 2008 · Updated 4:41 PM
By Ruth Longoria
Three stately Ulmus americana (American elm) trees on First Hill lost their lives last week, cut down in their 80-foot-tall prime after being infected with the dreaded Dutch elm disease.
City officials said there was no way to save the trees, which have graced the east side of the roadway on 72nd Avenue, near 29th Street S.E. for probably the past 70 or 80 years. The elm trees were cut down Tuesday and Wednesday, carted away and ground up in order to protect other trees from contracting the disease.
Dutch elm disease spreads through fungus (Ophiostoma ulmi) transmitted by bark beetles or tree root infestation. Not all bark beetles carry the fungus; however, those that do are lethal to elm trees. The fungus can start high up on the trees -- causing leaves to wilt and branches to die -- then travel downward and infect nearby tree roots.
Dutch elm disease has killed about a dozen trees on the Island in the past four years since the first case was diagnosed here, said Paul West, city arborist.
``It's pretty bad, it can destroy a row of big beautiful trees,'' West said. ``And, once it gets into a tree there's no way to stop it, except to cut down the tree.''
Trees infected with Dutch elm disease can't be turned into firewood or used for some wood projects, said Chris Berg, a worker with Seattle Tree Preservation, the company that cut down the trees for the city. ``You have to be very careful what you do with the cut down trees, because you don't want the disease to spread,'' Berg said.
Mainly, the tree chunks are ground up and burned, he said. However, the wood chips from the three Island trees will be taken, by a half-dozen truckloads, to Islander Middle School for use in landscaping projects beneath several Douglas fir trees, said Tom Otto, head groundskeeper with the Mercer Island School District.
Otto, who also is an arborist, stopped by the tree cutting site Tuesday afternoon as Seattle Tree Preservation crews in hard hats and carrying chainsaws, propelled up and down the trees. Otto and a handful of neighbors watched in fascination as 8- to-10-foot chunks of the trees were lowered on cables to the ground.
Otto said the Washington State University extension office was contacted prior to making the decision to use the diseased tree chips at the school.
``Evidently the fungus can't survive once it is exposed to air, through chopping up the chips,'' he said.
The city became aware of the problem with the 72nd Avenue trees after a homeowner asked the city to do something about some of the tree branches that were reaching down to his rooftop, said Jimmi Maulding, Mercer Island's street maintenance director.
``I was going to deal with that, but then, in talking with Paul West, he suggested I get the trees tested, since parts of the trees looked to be dying,'' she said. Lab tests revealed the fungus.
After the tree stumps are removed, Maulding plans to have other deciduous trees planted to line the street. Those trees should be planted this fall or early winter. ``But, whatever kind of trees we decide on, I'll make sure they aren't susceptible to disease,'' she said.
Although there is no cure for diseased trees, Dutch elm disease can be prevented. The city is currently treating another elm tree a few blocks from the diseased tree, on S.E. 32nd Street.
``I think we got to that tree in time,'' Maulding said.
A treatment for the disease can be injected into healthy trees every three years, similar to an inoculation, that will prevent the fungus. A tree care company, or arborist, can drill holes and pump a highly regulated pesticide into the base of the tree. The pesticide travels up the tree to the canopy and prevents the fungus from surviving. However, tree owners don't always take those preventative measures, West said.
``If there's any message people should get out of this it's to take the time and protect their trees,'' West said. ``Otherwise, once the fungus gets them, it's almost always too late. There've been a few cases of stopping the spread of the disease in newly infected trees, but it almost never happens.''
For more information on protection against Dutch elm disease, contact Paul West, city arborist, at 236-3544.