I contacted the nursery I purchased the trees from and they said wait until next year to prune or head. I have found, where I live, anything around the trunk of the tree - tree tubes, screen, etc - is an invite for fireants to set up house keeping. I have never had a tree trunk damaged by a chewing critter. We have squirrels - but no rats, mice, or rabbits. I have some fruit trees that have been in the ground for 15 years