I have several stumps in the ground left from chopped-down leylandii. The
stumps have been there for about 5 years. Under the soil, I think one of
the stumps has honey fungus (it's white and smells like mushrooms). The
surrounding plants are (touch wood) healthy. Should I treat the stump or
should I leave it? It can't really be removed without damaging surrounding
plants.

Thanks.