Tree Cankers

Question

We have a huge oak that has apparently lost a large branch on the side of the trunk. It looks like a canker, although I see no fungus. What can I put on the open area to seal the wound?

Answer 1

This article should help: https://www.gardeningknowhow.com/ornamental/trees/tgen/tree-disease-identification-sooty-canker-fungus.htm