We had a few saplings (choke cherry, maple and others) hit by a line trimmer (the bark was taken off in a small area near the bottom of the tree). We were wondering what we should do if anything to make sure they live.
Nothing - air is the best disinfectant. Any type of paint only seals diseases in the hole to do their damage the more. As long as the damage does not extend round the full circumference, they sould be OK. To avoid future accidents, remove all the grass from the base of the trees for a metre diameter, and put down some mulch instead.