EMERGENCY TREE ALERT!
You may have heard about the Thousand Cankers Disease (TCD) of Black Walnut. This pathogen requires both the western walnut twig bettle Pityophthorus juglandis and the gungus Geosmithia morbida in order to occur - and wherever one is found, the other is always present. TCD originated in the western states and is killing all black walnut trees planted there, and brings certain death for every black walnut in Illinois once it arrives here. No cure is known. It was discovered in Tennessee in 2010 and in Virginia and Pennsylvania
in 2011, almost certainly spread there by people carrying walnut wood from infected trees out west.
Symptoms of TCD include:
Premature yellowing of leaves or twig dieback, especially in the top of the tree;
Canopy thinning, where sections of the leafy canopy are thin or missing;
Tiny exit holes (the size of sugar grains) on branches - usually hundreds within a few
square inches;