Sunscald is the most likely cause, but there are other ways sections of tissue can die. Fungus decays the dead tissue over summer. A healthy tree walls off the dead tissue, so hopefully the fungus dies out after the dead tissue is consumed. The result is a canker spot like the one i n the picture. Some people bridge graft over extensive cankers on trunks, but I think that one will be okay as long as it doesn't get more damage on the good side. You might want to checkout the recent post on trunk protection. Here is a link that might be useful: Trunck Protection

Has anyone come up with an answer to this bark problem? I'm quite sure that it is neither squirrels, birds or large insects. I use D.E. to keep ants off. This has been gradually worsening over the last 4 years and, even though the tree produced some fruit this Spring, it is in obvious decline. Would tree paint help at all (unlikely), but perhaps some sort of trunk wrap? Once the bark separates, it is difficult to imagine the tree repairing itself, so maybe it's time to bite-the-bullet.

Contact your local office of the University of Connecticut USDA Cooperative Extension Service and have the horticulturist come out and look. While I've not heard the Emerald Ash Borer is in Connecticut that does not mean they aren't. These wee larva are devastating Ash trees in many areas of the country and are spreading out. Here is a link that might be useful: Emerald Ash Borer

You have quite the colorful garden growing on your apple tree! The bright green in the second picture and probably the dark green with little russet fruiting bodies in the first appear to be moss. The rest--pale green, dull light green, yellow-green, orange-gold, as well as the dusty white splotches, appear to be a variety of lichens. Lichens are associations of two or three distinct organisms (fungus, algae, and sometimes cyanobacteria) living in varying degrees of cooperation. They come in many sizes, shapes and colors. In general neither lichens nor mosses are thought to threaten the health of trees on which they live. I also live in northern California, at about 1500 feet in the Sierra foothills. Our area is sprinkled with black oak and several varieties of scrub and live oak. When cold weather comes and humidity rises, mosses and lichens suddenly become visible on all these trees. The more moisture we get, the more noticeable (and colorful!) the lichens become. Toward the end of a really wet season, the things are literally hanging off of the branches, like Spanish moss in the South. The one I marvel at most has long curly tendrils of bright glowing chartreuse. When the season changes again and things begin to dry, so do the lichens. Their seasonal extensions break, blow off, or dry up, and all but disappear--until the next rainy season. The oak trees never seem to mind. It's dark out right now, so I don't know whether or not we have lichens on our apple tree, but I wouldn't be surprised or worried if I saw them there. Scraping them off could very well injure a tree, allowing entry to a number of truly harmful organisms. The URL below may help allay your concerns. If you are still worried, you could call your local agricultural extension and make an inquiry. Sweetcicely Here is a link that might be useful: Lichen information