Dr. Tisserat examines dead walnut in Boulder, CO. Black lesions under bark are diseased area.
When you watch a television sitcom, you must suspend reality or risk driving yourself nuts arguing their implausible scenarios. Lucille Ball proved this weekly, as she and Ethel managed to get into some ridiculous shenanigans, as do the ultra-geeks on Big Bang Theory today. But when a sitcom takes an uneducated stand on a heartbreaking topic of tree catastrophe, well, any person who considers themselves a Lorax is bound to rise up in protest.
Such was the case on the show Last Man Standing, starring Tim Allen on ABC. Set in Denver, the show’s recent episode, Tree of Strife, took on the topic of Thousand Cankers Disease and the plight of the Black Walnut.
Thousand Cankers disease attacks black walnuts, and cities from Pueblo to Fort Collins are suffering losses. So far, towns to the east are spared but researchers at Colorado State University expect that it’s a matter of time before the disease spreads to Greeley and beyond.
Last Man Standing portrayed this disease as infesting a walnut branch thrown through their window by a severe storm; that the tree was owned by the city set up the story that the City of Denver required the show’s character, Mike Baxter, to cut down a walnut in his yard. The role of the tree branch was played by a Siberian Elm.
Intent on ridiculing city foresters, the show depicted the inspecting arborist as a smug bureaucrat with the ability to pet a branch to diagnose the disease. In reality, plant pathologists must pry the bark up, exposing the tunnels and blackened cankers. Holes from the twig beetle are tiny, and difficult to see. But after one glance at the downed branch, the forester condemned a nearby walnut planted on Baxter’s property as diseased and hazardous.
Allen’s character became indignant, not over the preposterous notion that any forester would condemn a tree willy-nilly, but because of the government telling a citizen what to do with private property. “I don’t like The Man telling me what I can or can’t do on my property,” said Allen’s character, evidently in favor of having a judge tell him he could pay damages after leaving a hazard tree up until it fell on someone else’s property and destroyed it.
The problem with leaving the diseased trees standing is the mobility of the walnut twig beetle (Pityophthorus juglandis) which carries the fungus, Geosmithia morbida, from tree to tree. Boring into branch and trunk, the beetles deposit the fungus, which kills with thousands of rotting wounds, called cankers.
“Slowly but surely, this is eliminating black walnuts here in Colorado,” said Dr. Ned Tisserat, CSU professor of plant pathology and disease discoverer. “It’s hard to know the final outcome, but the real threat is outside our state, to the billion-dollar black walnut timber industry.” Walnuts in Tennessee, Pennsylvania, Virginia, California, Oregon, Washington, Idaho, and Utah are infested. Nut-production walnuts appear resistant.
To be fair, there was a plea from the daughters and mother on the show to spare their tree’s life, evoking the emotional attachment many people feel for trees. Recounting tire swings and first kisses under its branches, the family fought city hall in a doomed attempt to block the order. Several cities in Colorado have requirements for removal of infested trees.
In the end, Allen’s character vows to replant his walnut, brandishing a seedling tree brought home for the purpose. It’s a ficus, which should provide the daughters with the poignant but powerful lesson on what happens to a houseplant when planted outside in our area. Most cities offer advice or a tree replacement program which feature trees best suited to the Colorado climate.
Gardening after five 