Yesterday, a van rammed into the cottonwood (I think that's what it is) and the protective bark was sloughed off. What should be applied to the area to prevent bacteria or insects from hurting the tree?
Tree Damaged by Car
Certified GKH Gardening Expert
Unless the tree has been fully girdled (bark removed all the way around the tree), it is best to let the wound stay open. Applying anything on the wound can actually trap bacteria in the wound and cause more damage than good. This article will explain more and have some tips for cleaning the wound: