Looks like you have aphids. Do a google search for: aphids control. Or search this site. I can't tell how big your tree is. If you can reach them with a hose, many people just spray them off with a strong spray of water. You can also use an insecticidal soap mixed with water which will suffocate them. They are quite delicate and have a number of predators. In small numbers they won't do any serious damage but they propagate quickly. They like young succulant growth which the drastic pruning and spring combine to make. If you look closely you may notice small shiny drops of clear sweet liquid on the leaves, ground, or whatever is beneath them. They suck juices from the tree and excrete that "honeydew". Ants like it and can be found fostering them.

The damage doesn't look very old. It's also not from an animal, since it's too high up (around 3 feet off the ground), plus we have a fence around it and a chicken wire collar guard. That's why I first thought of insects. But the wound seems very clean, i.e. no frass or anything. I can't take a picture until Friday since I've loaned my camera... maybe then.

Apple scab affects both the leaves and fruit. It could be something else but to tell we'd need more to go on. Here is a link that might be useful: apple scab pictures

Agree w/ken on the large leaves and I would not worry to much BUT the little baby leaf above that big leaf (2nd pic) what is going on with the very tip. How much water are you giving it in Salt lake. Apples need a lot of water. If not on a drip, dig a depression moat around the base of the tree and fill with water. Remove any grass or weeds from the trunk out to the edge of moat berm. Depth s/b about 2" deep and about 3' out from ONE side of the trunk(6' in dia.)now you can use the hose, water on dribble. Fill up the depression with water. Slow and deep. .......................................Use the "fruit and orchard forum" maybe it will work a little better for ya