thousand cankers disease survey: 2011-2012
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 followed the 2011 TCD Survey Guidelines released by the USDA Forest Service and PPQ in May 2011. We traveled the state, identified walnut trees, and examined 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 observed symptoms, we collected limbs and examined them for pin-sized, round holes and peeled off the bark to look for dark cankers and beetle galleries. If we had observed these symptoms, we would have collected several branches from the tree, wrapped them in paper towels or newspaper, placed them in Ziploc bags, and taken them to the University of Kentucky for initial screening for Geosmithia morbida and the walnut twig beetle. We did not detect the presence of thousand cankers disease or the walnut twig beetle in our survey in 2011.
The Kentucky Division of Forestry conducted a survey as well and also did not detect the presence of thousand cankers disease or the walnut twig beetle in 2011.
Number of Counties with Survey Activity: 19
Counties with Survey Activity: Barren, Bell, Boone, Campbell, Fayette, Grayson, Hopkins, Jefferson, Jessamine, Kenton, Knox, Laurel, Logan, McCracken, Nelson, Oldham, Simpson, Warren, Whitley
Number of black walnut trees examined: 1867
In 2012, the USDA approved a trap/lure combination to be used for trapping the walnut twig beetle; therefore, we established 29 survey sites using these traps in an attempt to detect the beetle that causes this disease. Thanks to the survey activities in 2011, we had a good idea about where to place the traps in 2012.
Number of Counties with Walnut Twig Beetle traps: 13
Counties with Walnut Twig Beetle traps: Barren, Bell, Boone, Clark, Edmonson, Fayette, Greenup, Jefferson, Knox, Laurel, Madison, Nelson, Warren
Number of Walnut Twig Beetles collected: 0
Click here for maps of thousand cankers disease surveys.
Damage from Thousand Cankers Disease of Black Walnuts