Untreatable fungus threatens Prosser walnut trees

PROSSER -- A row of five black walnut trees stand guard over the home of Gwen-Alyn Hoheisel.

They provide her neighborhood with shade and beauty. A sixth, located in her back yard, supports a rope swing for her 2-year-old son.

"They're great shade trees," says Hoheisel.

Still, she most likely will cut all of them down. Scores of other walnut trees that line the streets of this shady lane town may follow.

Hoheisel, a Benton County Extension agent, has determined many of Prosser's walnut trees have an untreatable fungus that will spread if left unchecked.

Called thousand canker disease, it's carried by a tiny -- 1 millimeter tiny -- beetle that bores into branches to lay eggs. This critter only likes walnut trees, so Prosser's maples, oaks and lyndens can relax.

The disease is common in other parts of the country. Colorado and California have been contending with it for about three years. But so far, nobody has come up with a chemical treatment or pruning method to stop it.

Hoheisel, a tree-fruit specialist, is asking residents of Prosser, the Tri-Cities and the Yakima Valley to call extension offices if they notice symptoms, such as leaves yellowing out of season and falling dead limbs. She hopes to eventually map the extent of the problem and doubts Prosser is the only affected town.

But it's possible. Prosser seems to have more walnut trees than neighboring towns.

There are 84 just in the city right-of-ways and parks, not including privately owned trees. That's a healthy chunk of the more than 1,000 city-owned trees that light up with color in the fall and help give the community its small-town look and feel.

"They're part of our urban forest," says Public Works Director L.J. DaCorsi.

DaCorsi and city leaders have not determined what to do just yet, but they will work on a plan over the winter. Unfortunately, he says, it may involve cutting down trees, an expensive solution. Removal can cost up to $2,000 per tree.

Next door, Grandview has no walnut trees on city property, though a few folks most likely have them in their yards, says Mike Carpenter, city parks and recreation director. Yakima and other communities in the Valley don't have many either, say tree removal specialists. The ones they do have are 50 years old or so.

"You don't really hear of people planting anymore," says Lance Forsee, owner of Colonial Lawn and Garden.

Forsee hasn't noticed any problems with the disease. If people complain about walnut trees, it's usually about the mess from the soft, fleshy coverings of the fallen nuts.

The fungus affects both black walnuts and English walnuts, as far as researchers can tell.

Prosser seems to have more black walnut trees while the other areas lean toward English walnuts, which have a sweeter, easier-to-crack nut. The same is true for the Tri-Cities area.

Neither variety is native to Washington or the West. Researchers fear that the disease could spread to the native trees of the northeast, Hoheisel says.

Hoheisel just attended a conference in Reno, Nev. Her alerts about the fungus prompted researchers to throw together an extra session about the walnut disease at the last minute.

Washington has little commercial walnut crop, unlike California.

However, Marv Durfey grows and harvests English walnuts from about 15 trees north of Prosser. He sells them for $1 per pound at farmers markets.

He hasn't noticed any problems yet, but it wouldn't surprise him. Growing up in Arkansas, he remembers diseases completely wiping out both native and farmed trees.

"These things happen, it's odd," he says.

* Ross Courtney can be reached at 930-8798 or rcourtney@yakimaherald.com.

What to look for, what to do ...

If you have a walnut tree in your yard, this is how you check for the presence of thousand canker disease and what to do if you find any:

What to look for:

* Yellowing or browning of leaves in sections of the tree during the spring and summer.

* Dead branches.

* Tiny -- 1 or 2 millimeter -- entry holes bored by the beetles.

* Dark brown or black stains in the cracks of bark.

What to do:

* Cut off several dying or dead branches, at least 1 1/2 inches thick.

* Bring them to your local extension office for testing.

* If you cut down a tree that might be infected, have it chipped or debarked. Storing the wood for firewood or worse, selling it, will only spread the disease.

To reach your local extension office, call the following numbers call 574-1600 in Yakima, 786-5609 in Prosser or 735-3551 in the Tri-Cities.