Hello Walter,
Thank you for writing to CSU Extension with your question about your apple tree. The photos are helpful, but I do have some questions for you:

1-When did you first notice this problem on your tree? Is the white cover soft; it appears to be, but could you confirm?
2-What kind of apple tree is it? How old?
3-It appears this tree is on your private property (not an orchard); is this true? Are residents responsible for trees on their property (if governed by an HOA)?
4-Is this the only apple tree you have?
5-It looks like the reddish "spots" on the trunk are actually lesions, where the bark is split and showing the inner layer of the tree (the phloem); is that true?
6- Anything else you can tell us about the tree that may be different from usual; leaves, has it produced fruit, etc.?

We want to be sure and give you the best information possible. With answers to the questions and other observations you can share, we'll work with you to help identify the problem and provide resources for a resolution.

Thank you!
Colorado Master Gardener
Boulder County