Thousand Canker in a Black Walnut Tree

Asked October 26, 2015, 4:22 PM EDT

I have a black walnut that currently has one limb that is completely dead and it a single dead leaf on the end of some of the other branches. I have been told by a tree trimming service that this is cause by a beetle out of Colorado and causes cankers on the tree, ultimately killing it. I would like to save the tree if possible. I was planning on getting all of the dead material removed, but I am wondering if there is also a way to kill the beetles themselves? Also, if we remove the dead wood, would we need to immediately burn the dead wood to kill the beetles? Or, is there another way to prevent the beetles from just moving onto the unharmed portion of the tree? Thank you so much for your advise!

Marion County Oregon plant disease black walnut tree

1 Response

There could be a few reasons for the dead limb but Thousand Cankers is quite possible. It is hard to tell when you got your diagnosis as trees look dead this time of year from normal leaf fall. Assuming your black walnut has this problem, there is no way to rid the tree of the beetles. It has been tried many times without success. There are many trees in the county with this disease so taking major precautions with the limb that is take out is not needed. You may have a lot of dieback over the winter from this disease in other parts of the tree. My suggestion is to wait until late next spring and access how much of the tree is still alive. The entire tree may need to be removed or less than you are thinking now. The only reason not to wait is if the dead limb is a potential hazard to life or property. Then you would want to have it removed sooner than later. More on this disease here:
http://pnwhandbooks.org/plantdisease/walnut-juglans-spp-thousand-cankers-disease-black-walnut-decline