There are small round symmetrical holes around the trunk of a crabapple tree. The holes go up the trunk about every 3-inches, up to the bottom row of branches. The tree is approximitly 6 to 7 years old. We have two crabapple trees and this problem is only on one of the trees. Just noticed the problem this year. I don't know the species, the trees were already here when we moved here in 2003. Bug or critter problem?