Not likely that your other trees would be infected from the tree in question. The organism that causes this is everywhere just waiting for an injury or any opening to take hold.

I won't treat my tree with a blow torch. It would kill the organisms in the wound if it got hot deep enough. But it would also kill more tissue. I don't see that helping but could be wrong.

Spraying with copper is sometimes recommended. But the extent to which this can help is unclear to me.

Thanks fruitnut. I'll hold off on the blow torch idea. I'm hoping that it will heal all the way. Still wondering if it is more likely to come back when it gets wet in the fall. It is good to know that it needs to start from an opening and won't just pop out of anywhere.
Thanks again.