No, it doesn't look like spit (little bubbles), I've seen that on a plant once before. This is a white "fuzz." And I've seen that white bug near it once or twice. I don't think it is spittle bugs, could a whitefly be like what I described or are they like tiny gnats?

Is this mint indoors? It is very difficult to grow healthy mint in a house. It appears to be in a wooden container. Does it have drainage holes? This looks like an unhealthy mint which has succumbed to a mold and possibly a slug, snail or caterpillar rather than an insect.

I have a mature apple tree that has white fuzz on the cut and ooze of the main trunk. Do you know what that might be and is the tree can be saved? Pictured below

It looks like the brown part at the end is dead. I would cut that off and fill this jar with water to give all of the nodes a chance to take root.