CAVITY FILLING: A tree cavity is similar to a cavity in your tooth. Without proper treatment, the situation will only get worse. Unfortunately, cutting down on sweets and brushing regularly will not help to prevent a tree cavity.In simple terms, a cavity in a tree is a neglected bark injury that can be the result of many factors. The most common are improper pruning, mechanical injury and storm damage. Storm damage and injury from gnawing animals and landscape equipment (lawnmowers and string trimmers) contribute to bark injury by tearing the bark from the tree trunk or branch. When bark injury has occurred, the exposed sapwood or heartwood is more susceptible to attack by fungi that initiate the decay process. Insects and animals such as raccoons, woodpeckers and squirrels that inhabit tree cavities utilize the tree wound as the front door to their new home. Carpenter ants, in particular, will excavate tunnels throughout the decayed portion of the tree and excrete wood preserving enzymes as they do so. While these preservatives are beneficial to the tree, the tunnels the ants create allow water to accumulate. Excess water simply facilitates the wood rotting process.