I have an English walnut that is approx. 5-6 years old. There is a White fungus growing in the collar from a branch I removed. Is it harmful or caused by moisture? The tree is 20 feet tall and is bearing nuts. In the state of Wisconsin.
Are you sure that tree is only 5 years old? Boric acid (aka bug powder) is a cheap and extremely potent anti-fungal agent that won't hurt the tree; just give it a poof or two as needed.– dandavisJul 19, 2021 at 23:17
I would put bleach on it to kill the fungus. A few applications would be good . If fungus gets into the trunk the tree will slowly die.