thousand cankers disease survey
In 2008, black walnut mortality in Colorado was identified as being caused by cankers that were associated with insect galleries. This disease complex is now known as Thousand Cankers Disease (TCD) and has a fungal component, Geosmithia morbida, and an insect component which is the walnut twig beetle, Pityophthorus juglandis. Several other states have seen walnut mortality associated with this disease including California, Oregon, Washington, Idaho, Utah, Arizona, and New Mexico. In July 2010, TCD was reported in Knoxville, Tennessee, causing dieback on black walnut. As a leading producer of black walnut lumber in the country, this disease is of great concern to Kentucky.
We will follow the TCD Survey Guidelines released by the USDA Forest Service and PPQ. We will identify walnut trees and examine them for symptoms of TCD (yellowing leaves in the crown, symptoms worse on west and south sides of tree, browning leaves attached to twigs, limbs dying back, sprouts growing from tree roots, etc). If we observe symptoms, we will collect limbs and examine them for pin-sized, round holes and will peel off the bark to look for dark cankers and beetle galleries. If we observe these symptoms, we will collect several branches from the tree, wrap them in paper towels or newspaper, place them in Ziploc bags, and take them to the University of Kentucky for initial screening for Geosmithia morbida and the walnut twig beetle.
In addition, in 2012 the USDA approved a trap and lure combination to trap the walnut twig beetle. We will establish traps in 15 high-risk sites statewide to monitor for this beetle.
Damage from Thousand Cankers Disease of Black Walnuts