Walnut Twig Beetle Discovered In Nebraska

Trees affected by thousand cankers disease initially exhibit yellowing foliage, followed by brown wilted foliage, branch dieback and tree death.

*This picture shows a Colorado walnut twig with twig beetle exit holes.

The Nebraska Department of Agriculture announced today that walnut twig beetle, a carrier of a fatal disease of walnut trees, was discovered in Gering. This is the first confirmation of the beetle in Nebraska.

Walnut twig beetles are tiny brown insects that feed under the bark, causing twigs to die.

“The walnut twig beetle actually is not a serious pest,” said Rachel Allison, Western Forest Health Specialist for the Nebraska Forest Service. “The problem is the beetles often carry fungal pathogens on their bodies, which can infect the trees they feed on. The resulting disease, known as ‘thousand cankers disease,’ causes trees to decline and die.”

Thousand cankers disease has killed walnut trees throughout the western United States over the past two decades. It was particularly devastating in the communities along the Front Range of Colorado, the majority of black walnut are now gone. The only walnut species native to Nebraska, the eastern black walnut, is highly susceptible to the disease. In addition to its use for timber, nuts and wildlife habitat, black walnut is commonly planted in community and rural landscapes.

Diseased trees initially exhibit yellowing foliage, followed by brown wilted foliage, branch dieback and tree death. Tree death occurs two to three years after initial symptoms appear.

“No diseased trees were identified in Gering,” Allison said. “However, trees may be infected for many years without visible symptoms.”

The twig beetles were captured in detection traps placed near walnut trees at the Monument Shadows Golf Course in Gering by Nebraska Department of Agriculture as part of their annual walnut twig beetle survey. More intensive detection efforts will be conducted in the coming weeks.

The Nebraska Department of Agriculture implemented a quarantine prohibiting the movement of walnut wood into Nebraska in 2010. The walnut twig beetle and canker fungus are easily moved long distances in diseased wood. Regulated material includes walnut branches, logs, roots, firewood, green lumber, bark, wood chips and nursery stock.

At this time there are no treatments available to control diseased walnut trees.

Find more on the Nebraska Department of Agriculture walnut wood quarantine here