In landscape design and maintenance, it is most certainly possible to have too much of a good thing. Properly used, mulch can enhance your landscape design aesthetically and reduce landscape maintenance requirements. But mounding up mulch around a tree to form a little volcano can damage a tree.
It has been pointed out that putting too much mulch around trees probably kills more of our beloved woody giants than do gypsy moths!
The very mention of "gypsy moths" makes many people cringe. I was lucky when my region had its worst outbreak of gypsy moths, back in 1981. I was overseas at the time, so I avoided the invasion. My parents told me horror stories of not wanting even to step out of the house, so overpowering was the gypsy moth presence! All I could think of was, "This is Alfred Hitchcock material!"