Damage to tree bark threatens the entire tree. Whether bark was grazed by your daughter's new boyfriend's car or damage appears to be insect-related, it needs prompt attention to keep your tree healthy. Find out whether injury to bark appears to be the cause of a problem or the result of one, and take measures to help your tree overcome the damage.
Determine the extent of bark damage and, if possible, the cause. Cooperative extension experts define small areas of damage as comprising 25 percent of the circumference of a tree or less. For areas of that size, which have been nicked by cars or construction equipment, they suggest trimming damaged bark edges cleanly and letting the area heal on its own. They note that previous attempts to paint or otherwise cover small wounds apparently make no difference in the healing process. Following best-care practices for watering, fertilizing and pruning provides trees with the strength to heal from small bark wounds.
Look for insect damage, especially if bark damage girdles the tree trunk or appears in a number of areas. Insect damage usually shows up as groups of small holes in areas where bark has peeled away. You may also find small piles of excreted sawdust ("frass") left behind by hungry tunneling insects.The Texas A & M Cooperative Extension Service lists a daunting number of boring and invasive insects whose depredations show first in bark damage. Consult your nursery or county extension for the right kind of insecticide to use in your area. Apply insecticide carefully according to directions.
Inspect your tree for damaged roots. Trenching for drainage or sewage anywhere within a tree's "drip line" (roughly the extent of its canopy) can damage roots that extend as far out as branches. Even parking heavy construction vehicles close to trees can crush roots, causing problems that reflect in the condition of the bark. Bank some extra soil over gouged, broken or exposed roots. Water regularly and fertilize to strengthen the tree's ability to overcome the injury.
Look over your whole tree when trying to diagnose bark damage. Look at upper branches for clues beyond what you have gotten from the trunk and roots. If you don't see obvious signs like large dead branches on your big trees, step back and get out your field glasses or binoculars. You may find splits where branches join, dead areas concealed by leafed-out branches and further signs of damage, like holes that suggest the tree is slowly dying from the inside and hollowing out. Having a picture of your whole tree, not just the damaged bark area you can see in front of you, will help you decide what action to take.