Heartrot is a common disease in forest and yard trees, turning potentially valuable trees into standing and sometimes dangerous culls. It is caused by a decay fungus that feeds on the wood in the center of the tree that is usually dark in color, called heartwood. That nice chocolate brown of black walnut furniture comes from the heartwood of that tree. The disease gets into the tree through a wound of some sort, and slowly over the years decays the heartwood out until it is hollow.
A wound caused by wildfire is the most common way heartrot gets started in a forest tree. Wounds from a fire normally occur on the uphill side of the tree where leaves tend to pile up against the base. This extra fuel makes the fire burn hotter right against the tree, causing a wound sufficient for heartrot entry. Thin barked trees like beech and red maple are especially susceptible to fire wounding and fungal attack. Needless to say, the best way to prevent heartrot is to prevent forest fires.
Another common wound source is timber harvesting. Felling trees and skidding logs are very physical activities and trees can be wounded in a number of ways: broken limbs, skinned bark from felling, road construction, skidding, etc. Damage to non-harvest trees can be minimized with a little planning, so make sure the logger is aware that you are concerned about the uncut trees.
Other activities that can cause wounds are firewood cutting and hiking trail construction. The bottom line is that whatever you do to the woods, do it carefully. Just remember what your Mom told you, those scratches and cuts can get infected.
For yard trees, the main way the heartrot enters trees is from wounds caused by lawn mowers and weed trimmers. I’ve seen more trees damaged by lawn equipment than I care to remember, and the problem seems to be time. Home owners and commercial lawn care people get in too big a hurry and ding up the tree. If the trees aren’t killed by girdling outright, they get heartrot, which weakens the trunk creating a hazardous tree that could come down during a storm and harm homes or people. So slow down people! Don’t let the equipment touch the bark! Use mulch or herbicides near the tree trunk to control grass and weeds and keep the machines away.
A few hollow trees in a forest can be a good thing, supplying den trees for squirrels, several bird species, and raccoon. Having 2 or 3 per acre will provide plenty of cover for wildlife, so many more than that hurts the health and value of the forest. . If you need assistance with keeping a forest healthy and productive, call your state forestry office.