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Thousand cankers disease in Central Valley
UC Cooperative Extension orchard systems farm advisor Elizabeth Fichtner believes farmers should monitor their walnut orchards for signs of thousand cankers disease. Infected trees, she says, should be cut down and burned.
Thousand cankers disease has been threatening black walnut trees in 15 California counties for several years; six infected trees were found in Tulare County since last year, according to an article in the Visalia Times-Delta. Fichtner said she began finding the disease in Fresno County a couple of weeks ago.
The fungus has also been found in Arizona, New Mexico, Colorado, Idaho, Oregon, Utah and Washington state. It was detected in Tennessee in July.
"We really don't know where it came from," the article quoted UC Davis entomologist Lynn Kimsey.
Fichtner said the disease is spread by the walnut twig beetle, which burrows below the bark to make spaces to breed. The fungus spores are carried on their bodies when they enter the tree.
The first symptoms are the cankers, each with a tiny beetle burrow hole at the center. Later leaves yellow and branches die. Because there are no known treatments for the fungus, eventually it kills infected trees.
On the bright side, one infected tree doesn't mean the whole orchard will succumb. Fichtner told the reporter that the walnut twig beetle produces an aggregation pheromone, so all of the beetles tend to attack one tree.
Nevertheless, research entomologist Steve Seybold of the USDA Forest Service Pacific Southwest Research Station said the disease is pervasive in many California cities and towns.
"I really don't see much hope for combating this disease," Seybold was quoted.
More information about thousand cankers disease is on the UC Davis Department of Entomology website.
Thousand cankers disease has been threatening black walnut trees in 15 California counties for several years; six infected trees were found in Tulare County since last year, according to an article in the Visalia Times-Delta. Fichtner said she began finding the disease in Fresno County a couple of weeks ago.
The fungus has also been found in Arizona, New Mexico, Colorado, Idaho, Oregon, Utah and Washington state. It was detected in Tennessee in July.
"We really don't know where it came from," the article quoted UC Davis entomologist Lynn Kimsey.
Fichtner said the disease is spread by the walnut twig beetle, which burrows below the bark to make spaces to breed. The fungus spores are carried on their bodies when they enter the tree.
The first symptoms are the cankers, each with a tiny beetle burrow hole at the center. Later leaves yellow and branches die. Because there are no known treatments for the fungus, eventually it kills infected trees.
On the bright side, one infected tree doesn't mean the whole orchard will succumb. Fichtner told the reporter that the walnut twig beetle produces an aggregation pheromone, so all of the beetles tend to attack one tree.
Nevertheless, research entomologist Steve Seybold of the USDA Forest Service Pacific Southwest Research Station said the disease is pervasive in many California cities and towns.
"I really don't see much hope for combating this disease," Seybold was quoted.
More information about thousand cankers disease is on the UC Davis Department of Entomology website.
Walnut twig beetles carry the deadly fungus into trees. (Photo by Kathy Garvey)
