Tree Indentations

I noticed small indentations on my tree's trunk. What may be causing them?

—Callie Audrews, DeQuincy, Louisiana

Melinda:

Take a close look at the spots—if they appear flaky and on the trunk's surface, they are lichens.

A combination of fungus and blue-green algae, these organisms do not harm the plant. In fact, it's best to leave them in place because scraping them off can injure the trunk.

Sunken and discolored areas, on the other hand, are cankers. Often caused by disease, a telltale sign of cankers is stunted or misshapen leaves on the infected stems.

Removing cankered stems is the only solution. Prune at least 6 to 12 inches below the canker or back to where the diseased stem joins a healthy branch. Disinfect tools between cuts.

If the canker occurs on the main trunk, however, all you can do is care for your tree to prolong its life. consider consulting a certified arborist if you think cankers are the problem.