I have a Red Spire Pear tree that has been planted approximately 7 years ago. It is about 20 - 25 feet tall with a trunk diameter 8 - 10". The bark has separated from the tree in a section about 12" by 9". I cannot see any sign of insects and the tree appears to be healthy --- not loss or turning color of leaves, etc. A similar tree was planted about 20 feet away at the same time and has no problems. Any suggestions?