If you have just pruned a birch tree, or found an open wound on one, you can seal the wound to protect the tree from parasite infestation. Most trees do not require sealer during the healing process. But birch trees have very thin, fragile bark that easily peels away if damaged, so sealing their wounds is beneficial. Use a non-asphalt tree sealer on birch as asphalt sealers will damage the trees.
Cut away any loose bark around the birch tree's wound or pruned area with a utility knife. Loose bark will not reattach and it serves as a breeding ground for bacteria and infestation.
Wash the damaged area on the birch tree with tap water with a few drops of dish soap mixed in. Use a sponge or rag to clean the wood. Wipe the wound dry with a towel.
Squeeze the non-asphalt pruning sealer over the wound on the birch tree, then spread it out with a small paintbrush until the entire wound is covered with a thin coating of sealer. Overlap the sealer on the surrounding bark to ensure you cover the entire wound.