Our apple tree has sections of white fluff along many of its branches. In some places it is quite concentrated; in other places it is scarce but evident. The fluff seems to be entirely along sections of branch that were scored and split by last year's cicadas. We did not cover this tree and it was infested. The tree is 10-12 yrs old, planted in full sun and is otherwise healthy. It is not planted in a spot that skews wet or dry; it's on flat ground in front of our house. What is it? Thank you.