In most cases, pruning sealants provide no benefit to tree health and may even incite stem decay or inhibit wound closure.
When pruning cuts are properly made, they seal quickly with minimal effects on tree health. The tree will surround the wound internally with chemicals and physiology that form a barrier to microbe movement and externally with new decay resistant wood helping to reduce the spread of decay.
Sealants may be warranted for use on oaks in certain parts of the country where oak wilt disease is problematic. Consult with your local Extension office to determine whether oak wilt or other diseases that infest pruning wounds are prevalent in your area.