PROSSER -- A deadly fungus discovered last year in Prosser continues to wreak havoc on the city's walnut trees.
Worse yet, there's no known treatment.
Thousand canker was discovered in Prosser last summer when a Washington State University Extension educator found six walnut trees on her property were infected. They eventually were removed.
Now, many of the about 80 walnut trees on city property show signs of infection: Yellow leaves, dead, barren branches and flagging limbs. Walnuts make up a little less than 10 percent of the trees on city property.
The city has removed three black walnut trees this year and plans to continue.
"We expect to be removing dead trees for some time," City Administrator Charlie Bush said. "Our primary strategy at this point is to take them out when we can."
The city budgets about $15,000 annually for tree care, which includes removal, planting, trimming and maintenance. Removal costs about $3,000 per tree, so the city can only cut down a handful of diseased walnut trees each year.
"You don't get a lot of bang for your buck," said L.J. DaCorsi, Prosser Public Works director.
Thousand canker is spread by walnut twig beetles, which bore in to the tree and feed on tissue under the bark. After the beetles bore into the tree, the fungus takes hold and causes thousand canker disease.
The disease has ravaged areas of Colorado's Front Range and has been found elsewhere in Washington, Arizona, New Mexico, California, Oregon, Utah, Idaho and parts of northern Mexico. Thousand canker takes about one to three years to kill a full-grown walnut tree.
"It's something you see gradually," DaCorsi said.
WSU Extension instructor Gwen Hoheisel discovered thousand canker in Prosser last year. She said little can be done to save infected trees.
If the disease is detected early, Hoheisel said the affected limb can be removed, which couldprevent thousand canker from spreading. She said the beetles often spend winter holed up atop the tree inside its bark. As the weather warms, the beetles emerge and bore into lower limbs and the tree's trunk.
Once there, not much can be done.
Experimental techniques, such as using insecticide or fungicide injections, have so far proved ineffective.
Instead of treating the disease, Hoheisel recommends taking a preventive approach, such as regularly watering a tree, treating it with a systemic insecticide and giving it nutrients.
Although thousand canker is most prevalent in Prosser, there are signs it has moved toward the Tri-Cities. "There's not a doubt in my mind it's in the Tri-Cities," Hoheisel said.
An official with the Kennewick Public Works Department said he hasn't seen the disease in Kennewick. However, Tim Werner, Richland's parks and facilities resource manager, said a tree removed from a private residence in Richland earlier this summer appeared to have died from thousand canker.
"Every indication was (thousand canker) is what caused it," Werner said, adding that not many trees on city property are walnuts.
The disease also has been found in Yakima and Walla Walla, Hoheisel said. Howard Madsen, owner of Artistic Treeworks, hasn't seen the disease in the Tri-Cities, but believes it's there.
"For things to show up, it has to be here for a while," he said, explaining that thousand canker's presence in the Tri-Cities may be too premature to produce damage on trees.
In Prosser, city officials are toying with ideas about what to do with the trees. The decision to cut them down has been made, but Bush is hoping to find a company that'll remove the trees for free -- instead of getting a check, they'd get the valuable walnut wood.
Hoheisel warned against transporting diseased wood, but said there are methods to reduce the chance of spreading the disease. She said fallen wood can either be chipped, de-barked or pasteurized by placing the timber under dark, plastic sheets for months during the summer, so the extreme heat kills the beetles and fungus.
Until a treatment can be found, the city of Prosser is going to continue chipping away at the problem by removing dead trees.
"Obviously dead trees are an issue in parks," Bush said. "Limbs can fall off."
Hoheisel is working to spread the word about thousand canker. "I think a lot of people don't know about," she said.
If someone thinks their tree is infected, Hoheisel suggested using a razor to slice a strip of bark off a suspected limb. If there are beetles, there could be thousand canker.