The Eastern black walnut is a species of flowering tree in the hickory family that is native to eastern North America.
Under forest competition it develops a tall, clear bole and the open-growth form has a short bole and a broad crown.
The bark is gray-black and deeply furrowed.
Early symptoms (late June to late August) may appear anywhere in the tree crown (upper, middle or lower)
A portion of the crown may look thin
Look for yellowing and/or wilting leaves ("flagging") in the crown
Attached, wilted and brown leaves may be observed in the older portion of the affected crown
Leaves may appear smaller than normal
Actively declining crown symptoms
Over several weeks, there is a rapid wilting and "collapse" (of foliage) on affected limbs
Cankers may be observed on branch below wilting foliage
Dead limbs are relatively recent, usually died within the same season but not more than one year
Tree affected the previous growing season has little live crown the next growing season
Affected black walnut trees die in less than 3 years after the very first flagging symptoms are observed
Branches > 1 1/2 inches have numerous tiny holes (smaller than pin hole borer type holes)
When outer bark is carefully scraped to reveal inner bark tissue, small cankers are observed on branches. Once coalescing of cankers occurs, large, dead (cankered) areas can be found on branches and main stem
Numerous, meandering tunnels and galleries of the walnut twig beetle may be observed in the bark
Both the fungal cankers and the walnut twig beetle are found in the bark down to the cambial region (not into the wood)