On the trunks is a dark gray, foul-smelling, fluffy or powdery, slightly damp substance that eventually ends up on the ground in a ring around the base of the tree.
Same thing happened last October, but not in prior years. Elms planted about 25 years ago. Researched a dozen "tree" books; found nothing. What is this substance? Thank You.
Sooty mold is the only thing that comes to mind from the discription. Good luck
Do a google search to find your state's cooperative extension service, and call them. Most offer free gardening advice, and are likely to have information about plant diseases that are specific to your area. Much better than guesses from all over the country.
That's good advice but I believe that the opinions from this group are correct: sooty mold fungus. Did a google on the critters and that's what it seems to be.
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