Canby Herald Online

Bug battle producing casualties

Black Walnut trees are dying in the area and researchers think they know why

• By: John Baker  
• Published: 7/31/2009 5:55:47 PM

Photo By: Peggy SavageDying breed
Black Walnut trees at Barlow House will be removed soon due to being victimized by what is being termed Thousand Canker Disease

There's a battle raging in Oregon and its effects are being felt locally. Willamette Valley black walnut trees are the front line in this battle, which pits scientists against a small insect.

A band of researchers from Oregon State University are in and around Canby looking to get the upper hand in a battle that's claimed many casualties already.

“We've been having a Black Walnut problem,” said Jay Pscheidt, an Oregon State researcher with the Department of Botany and Plant Pathology, “where the trees will get thin and suffer 'dieback' (dead branches in the tree where there were none before). These are huge trees and some have historical significance and some are just very old. They are not easy to remove and are something people want to keep.”

He said the trees can have emotional value to their owners, neighborhoods and cities. Losing them hurts.
A group of trees along Territorial Road were recently felled and Pscheidt hopes to get a look at them this weekend to see if they have been victimized by the disease. Odds are, he said, they have been.
Pscheidt said they've seen a huge jump in black walnut tree deaths over the past six years and that got everyone's attention.

“We saw a flush of dying in the early 1990s, but were unable to figure out what was going on,” said Pscheidt.

That isn't the case this time. Research of the disease has led to the discovery of a new-to-Oregon beetle - the Walnut Twig Beetle.

“The funny thing is that the twigs these guys go after can be a couple feet in diameter,” Pscheidt. “There's a fungus associated with these beetles and we think that the beetle is transmitting the fungus and that fungus is working its way down the tree and killing it -- similar to Dutch Elm Disease.”

Colorado researchers who discovered the beetle and fungus will actually be in Oregon this weekend, touring several sites with Pscheidt, including the Territorial Road site.

“Between the two of us, we feel we'll be able to figure out what is going on,” said Pscheidt of his guests. “The poster child for this disease is the Barlow House, that's the one people recognize and its trees are declining very rapidly. We believe it's due to this disease.”

The owners of the Barlow House said they would soon be removing all but two of their Black Walnut trees after battling to try and save them. Once the disease gets into the trees, however, there is little anyone can do but watch and wait for the inevitable.

In fact, Pscheidt said that Black Walnut trees in Canby, Barlow and Aurora are showing signs of the disease. He's also seen cases from Corvallis to Portland to The Dalles, and heard of cases in LaGrande. The battleground has been established - Oregon's Black Walnut trees are under seige.

Last summer, Boulder, Colo. lost more than 70 percent of its Black Walnut tree population and continues to try and find a remedy for the spreading disease.

Pscheidt would like to make inroads now to prevent a similar fate later.

“It appears to be widespread (in the Willamette Valley) and we've seen the beetle in all these cases and confirmed the fungus in each case,” Pscheidt said.

But what to call it? The working name of the disease has been Black Walnut Disease, but the official name is Thousand Canker Disease. The beetles burrow in and the hole gets a brown discoloration, which scientists call a canker.

And it's that disease that will bring Pscheidt and other researchers to the Canby area this weekend as they examine trees in the area.

The race to slow down or stop the disease is on and researchers hope Canby's fallen trees will yield more clues toward that.

“One of the things we're seeing is a slower decline than what they describe in Colorado,” Pscheidt said. “They are dying within a year once the disease takes hold in Colorado. We don't see them decline quite so fast here. There might be a light difference in genetics or something else that slows it down. We'll look at the Territorial Road trees and see if we can confirm tree and fungus.”

 

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