Cherry tree disease

[Incy]

Hi,
I'm not very experienced when it comes to fruit trees and was hoping someone here might be able to help. We have a 3 year old dwarf cherry I think it is stella and it has some worrying looking lesions on it's trunk. The bark has split and it looks as though it has swollen in that section. It is not secreting anything that I can see and there are healthy looking buds on it both on the branches above and below this area. I have tried to take some pics, I'm afraid they're not great but hopefully show enough so that someone might be able to help.

[Glutton4...]

Looks like the kind of damage you get from rubbing branches. Has anything fallen against the tree over the winter?

[FB.]

Pics are a bit awkward to see properly, but it might be frost-related damage (my plum tree suffered some bark splitting during this recent hard winter). It's also possible that it's canker.

[Incy]

Nothing has rubbed against it but it has been exposed to the hard frosts. Should I just leave it alone or will it need treatment.

[FB.]

Unfortunately, the camera has focused on objects in the distance.
From that picture, it is difficult to tell if it's frost damage or canker (or something else).

I suspect that it's probably canker, but there's no way to be sure without a sharper picture.

A canker in such a location is difficult to deal with, since you'd have to cut the entire top off the tree, which may shock a dwarf variety so severely that it never recovers.
I doubt that any sprays will kill the canker because it will now be deep into the wood of the tree.

Without better pictures, my suggestion is to watch it closely.
If it's canker, it'll probably increase in size. The branches above the canker may die back, or become stunted as the canker blocks the sapflow.
You may find that buds a few inches below the canker will sprout, as the plant attempts to re-grow what is dying.
If it is canker, a copper/fungicide may help slow the progress and limit the spread to other parts of the tree, or nearby trees, but copper is highly toxic - including toxic to all the beneficial garden creatures.
You also have to be careful when using sprays, since some can be absorbed into the fruit. In fact, it's frightening when you realise just how much chemical residue is in the fruit that we eat; commercial orchards spray dozens of times per year and inevitably, some of it remains in the fruit.

I have an Ellison's Orange apple on a medium rootstock (MM106) and it got a severe and fast-growing canker on the trunk, just beneath where the main branches join the trunk. In a matter of several weeks, the canker had enlarged to almost go the whole way around the tree. The upper branches began to look sick as the canker cut off their water and nutrient supply.
To save the tree, I had to cut the whole top off, a few inches below the canker. Once upon a time it was 7-8ft. Now it's 2-3ft.
Fortunately, it's on a medium rootstock, so it should be vigorous enough to recover from the trauma, although it will take a few years to get back up to size. Funny thing is, I only keep the Ellison because it attracts the apple maggots - yes, you read that right!
It's so popular with the maggots that the most of my other apple trees are completely untouched. It's a sacrificial plant.