How do we save this apple tree?

Question: We're in a marine climate (5-minute walk from the ocean) and we have two trees, different cultivars, the younger of which isn't doing so well. It had lost many of its leaves already as of October, and the apples are very spotty. (The tree also has a bad lean, which we've countered with a stake and rope since the photo was taken.) It looks like it might be a case of apple scab, in which case I've read the recommendations and am prepared to act on them, but could still use some confirmation of this (as I'm an internet-educated novice). Or is it something else? Or there are multiple things wrong? In short, all suggestions are welcome. We're aware they need pruning; we've been gradually bringing them in line after several years of neglect before we bought the place.

responder: Jay W. Pscheidt, PhD, Professor  Replied November 12, 2024, 7:38 PM EST
response: Well, you certainly have apple scab based on the images of the fruit close up. The landscape images of the leaning tree tells me you are setting too much fruit. The root stock is likely a size controlling rootstock keeping the whole tree small. The heavy fruit set is likely contributing to the lean. Propping it up will help. Next year will not get as much fruit but thinning should help the situation. The trunk kind of looks like it may be cracked. If so it might be the reason for the poor growth and lack of leaves. I would be concerned with a root rot, collar rot or internal decay. Not enough information in the images to tell one way or the other.

responder: The Question Asker Replied November 13, 2024, 7:35 PM EST
response: Thanks for the reply! Here are some closer & more recent pictures, showing, among other things, the fact that we've picked the fruit, the rope we're using to prop it up, the lower trunk, and the upper trunk which I'm now noticing for the first time has, not just one but several, longitudinal splits in the bark, some old some new. Ai yi yi. Contrary to how it appears, the trunk is (at least) not touching the stone wall. If it helps I can dig down and show the root collar and/or roots, or if you can tell me the signs of root-rot to look for, I can look for them. Thanks so much.

responder: Jay W. Pscheidt, PhD, Professor  Replied November 13, 2024, 8:05 PM EST
response: Lots of things to see in the images. There is a burr knot about half way up the trunk. Not a big problem but something to watch. https://pnwhandbooks.org/plantdisease/host-disease/apple-malus-spp-burrknot There are cracks but the ones with callus formation in them are ok, just showing stress from the weight of fruit on the canopy. The depressed crack(s) are more of a concern and could be symptoms of anthracnose: https://pnwhandbooks.org/plantdisease/host-disease/apple-malus-spp-anthracnose-bulls-eye-rot The base of the tree at the soil looks like the soil level is a little high. We like to see trees planted such that the orgninal soil line in the nursery is the same when planted in the landscape. Its muddy but could be an issue. Digging away some of the mud would be in order as long as water does not puddle in the hole. Collar rot could be the issue:https://pnwhandbooks.org/plantdisease/host-disease/apple-malus-spp-crown-collar-rot Hard to tell from the images but it loos like there could be insect holes in the trunk. You would have to look closer to find those and see if they are a problem or not.