Wood decay is common on many species of shade trees. Wood decay fungi usually enter the tree through wounds. Most fungi grow rather slowly showing no evidence of being present until extensive areas are rotted. Most will first invade the non-functional heartwood. After decay is well advanced in the heartwood, they may invade the living sapwood.
When the fungus has developed extensively, fungal fruiting structures, commonly called shelf fungi or conks, may appear on the trunk. Some fungi may form mushroom-type structures at the base of the trunk or form on major roots, rather than on the trunk.
Where extensive wood rot has already occurred, the rotted wood should be completely removed. The cavity then should be sprayed with a fungicide and filled by a reliable and experienced tree surgeon.
Improper pruning or failure to remove wind damaged branches is a common problem that results in fungal infection. Do not leave branch stubs. Cuts should be made even against the trunk so that callous tissue can grow over the wound. Cuts should be made so that the scarred area will never collect and hold water.
Consult the Chemical Control Supplement (B-1140A) for specific chemical control suggestions.