Homegrown, yours is a good question. Here's what we seem to know: Large wounds on trees, like those pruning wounds on your oaks, are indeed hard for the tree to close off. Trees don't "heal" their wounds, they close them off with new tissue and with chemicals that plug the cells, sealing them off from infection by decay fungi. Copper is indeed a means to accomplish this, and one fellow I know who posts occasionally on the Conifers and the Trees forums has created his own "Liquid Copper Fungicide" and has used it likewise to protect pruning wounds so large that the trees normally wouldn't be able to close them off before decay set in. His is a lonely quest to convince the world that he has actually come up with something that works, and only because I know him to be a concientious and knowledgable person do I think he might be on to something.

In other words, all other treatments that have been suggested over the decades-shellac, asphaltic "tree paint", etc, have been shown to not be helpful. I really don't know if a copper in solvent material like you have would work, but I am concerned that, if I'm reading you right, deacy has already commenced. If this is so, I strongly doubt it can be halted.

Maybe share a little more info about where things are at here. Might be able to offer more.

+oM