
Often yes, if under roughly a third of the circumference is dead and the canopy above it is still full. Do not paint, tar, or wrap it; trees seal wounds inward from the edges and dressings trap moisture against the wood. The useful work is removing whatever is still stressing the roots — pull back a deep mulch ring, water deeply through drought, stop the mower damage. A tree losing bark most of the way around, or showing dead branches directly above the bare strip, has already made the decision for you.
Slow signal, not a countdown — nothing meaningful changes in days or weeks. Across one to three seasons, decay fungi work into the exposed face, the trunk loses cross-section there, and branches above the dead zone die and become the actual falling hazard. Recheck each spring: a growing roll of callus at the wound margins means the tree is closing it; an expanding bare patch plus a thinning canopy means it is not.