Sick Cherry Tree

[clv101]

I have a 5 year old Morello cherry on Colt rootstock. It was bought/planted winter 2012/13. It didn't look great last year but is much worse this year. I had lots of blossom this year, that all gone now but it hasn't set any fruit. I have another Morello nearby which has. Here are a few photos:

The tree:


Tip of a branch, these are the only leaves:


Dead blossom with no set fruit:


Any idea what might be wrong with this tree? And what I might do about it?

[WendyC]

Poor tree, is certainly looks to be suffering. Is there anything on the bark? I'm no expert (hopefully one will be along soon) but could it be canker?
https://www.rhs.org.uk/advice/profile?PID=86

[fishpond]

Looks the same as my Pluot.
Produced loads of blossom and leaf, 3 weeks later, no live blossom or leaves, looked completely stuffed, then I noticed it was alive with aphids. (this was quite early on in the year)(last year the squirrels ate the 5 nearly ripe fruits). Just left it thinking if it didn't recover I have a pear tree that would go there
This week, no aphids to be seen, no obvious aphid predators except for a pair of blue tits, also new leaves are showing.
It lives until at least next year.
Look for disguarded aphid skins on leaves (white in colour), you may find a few.