Karen, I have not seen this myself. If it is only one leaf, I would not worry. Looks to be some environmental issue and not bugs to me.
If leaf was at lower extremities of tree, could be completely normal.
Rick
"Many times a day I realize how much my own outer and inner life is built upon the labors of my fellow men, both living and dead, and how earnestly I must exert myself in order to give in return as much as I received"
