mold on base of red maple
(see image) There is mold around circumference base of tree. Much mulch around base and bed. Tried to hose it off. White stuff blew away. However, black/brown stuff EXPLODED into a massive (not kidding) cloud of brown spores (like a puffball does) and traveled with the wind all over the bed. Hosed the mulch/ground down but the very next morning, it was all back (again, not kidding). Big box store said 'too much mulch, scrape it all away and bag and toss it.'and said 'mold likes decaying stuff and water and all you did was 'feed' it.' What about spraying bleach or roundup on it? What can be done?
Lichens and fungus do not generally cause any harm to trees or plants.
Here are some links with more information.