March 5, 2015

Pest spotted in Colorado may endanger Nebraska walnut trees

Walnut Twig Beetle

Walnut Twig Beetle

While Nebraskans are being warned about the emerald ash borer that destroys ash trees, yet another invading insect is causing a stir as it could threaten our walnut trees.

Entomologist Robin Pruisner says a pest called the walnut twig beetle is now confirmed in neighboring Colorado, but it hasn’t yet been spotted in Nebraska.

“Research is ongoing on how to protect walnut trees,” Pruisner says. “We just don’t have a lot of answers. This is even newer than the emerald ash borer at this point in time.”

The walnut twig beetle carries what’s known as “thousand canker disease,” which is deadly to black walnut trees. There’s been no way found to reverse the disease or to kill the beetle without also killing the trees.

“The geosmithia pathogen is actually very common in our environment and this is just kind of a new cousin of that,” Pruisner says. “The walnut twig beetle is native to the southwest United States and down into Mexico.”

For many years, the beetle was only found in states like Arizona, California and New Mexico. Now, the rice grain-sized pest is being found well beyond the southwest, in states as far away as Virginia, Pennsylvania, Ohio and Tennessee — and next-door to Nebraska in Colorado.

Iowa is one of the nation’s largest producers of black walnut, prized for its grain and color,¬†and Pruisner suspects the insects are moving such great distances because people are enabling them to hitch long rides, perhaps right through Nebraska on Interstate 80.

“Aunt Sally out in Colorado has a walnut tree that dies in her backyard but Cousin Ed in Iowa would like to make a coffee table out of it,” Pruisner says. “This is the kind of thing that people throw in the back of their truck and they drive to Iowa and they could be inadvertently bringing along with it thousand canker of walnut.”

One way to stop the spread is to only use local firewood in campfires.