Question
I LIVE ON THE GULF COAST IN ALABAMA. I HAVE A WATER OAK, MAGNOLIA, AND A POPCORN TREE. THEY ARE ALL AROUND 20 YEARS OLD. THE OAK MAY BE OLDER. TWO ARE IN MY FRONT YARD, ONE IS IN THE BACK YARD. I HAVE NOTICED IN THE PAST YEAR THEY STARTED GETTING LIGHT GREEN SPLOTCHES ON THEM. IT HAS SLOWING BEEN MOVING UP THE TREES AND ON THEIR OTHER LIMBS. I AM CONCERNED ABOUT THEIR HEALTH AND SAFTEY. HELP

Answer
These are lichens and not a problem.
Lichens are organisms consisting of a fungus and a green or blue-green alga growing together in a mutually beneficial, symbiotic, relationship. The entire structure, called a thallus, is so different structurally from either of its partners that microscopic examination is necessary to distinguish the fungus and the alga.

The fungus obtains water and minerals from the air and the material it is growing on. The alga provides carbohydrates and vitamins. Some blue-green algae fix nitrogen that is used by both the alga and the fungus. Nitrogen is also obtained from bird excrement, organic debris, or plant leachate.

Lichens may be flat, leafy, or branched and hairlike. All three forms occur on tree bark as well as on rocks, soil, and other substrates. Colors may range from white to gray, red, green, yellow, and black.

Although lichens grow on tree bark, they are not parasitic (disease-causing organisms), and do not harm trees. The fact that lichens grow rapidly when exposed to full sunlight may explain their profusion on dead trees. The one conclusion that may be drawn with certainty from lichens on trees is that the air nearby is relatively pure. Most lichens will not grow in a smoky or polluted atmosphere.

Here is a web link to more information on lichens
http://www.backyardnature.net/lichens.htm