Tree owners warned about Dutch elm disease

Seattle officials are warning owners of elm trees to be on the watch for signs of Dutch elm disease — a killer beetle-borne fungus that has re-emerged across the city.

The disease has been confirmed in Seward Park, Kinnear Park, Maple Leaf and West Seattle, the city transportation department said in a news release Tuesday.

Several large diseased trees in city parks are being cut down — the only way to halt the spread of the fungus once it has spread to 20 percent or more of the tree, said City Arborist Nolan Rundquist.

The fungus causes a tree's immune system to stop circulating water, causing excessive wilting or dropping of leaves at the crown of the tree, Rundquist said. The browning of leaves usually starts at the tips of branches and works its way down the tree, ultimately killing it.

"What kills the tree is its response to the fungus. It tries to wall off the fungus," Rundquist said.

The disease, first identified in Seattle in 2001, is often spread by the elm bark beetle, which feeds and nests in elm wood.

Seattle isn't the only local city affected by the disease. The city of SeaTac removed 18 elms recently that had been planted along Des Moines Memorial Drive after World War I to honor those who died in the war.

The city has worked with the World War I Memorial Committee to remove the trees and replace them with 24 disease-resistant American elm trees.

In Seattle, city staff are available to inspect and test elms on public property and can provide limited visual inspections of trees on private property.

Private tree owners may have to pay for a $25 laboratory test to confirm a diagnosis of Dutch elm disease, but Rundquist said he or other city staff can usually spot the symptoms with a visual inspection.

Seattle's transportation department offers these tips for helping stop the spread of the disease:

• Do not prune elm trees between April 1 and Oct. 1.

• Remove dead branches from elm trees in late winter or fall to limit the breeding habitat of the bark beetles.

• Do not store elm wood as firewood unless the bark has been removed.

• Remove your tree within 10 days and dispose of it properly if the tree is diagnosed with Dutch elm disease.

Seattle residents who suspect an elm tree is diseased are encouraged to call the city's urban forestry department at 206-684-TREE (8733) or e-mail seattle.trees@seattle.gov.

Seattle Times Staff Reporter Susan Gilmore contributed to this report.

Jim Brunner: 206-515-5628 or jbrunner@seattletimes.com