Plum Leaf Problems

Hi
Can anybody tell me what has happened to leaves on my Plum Tree.
They were fine a month ago and now look like this.
Can I spray or leave alone for next year or what ??

Thanks for any advice

 

Looks like greenfly, at this time of year I wouldn't bother spraying, the leaves will drop off in a few weeks anyway, presume you are in South Yorkshire or North Lincolnshire. Once fallen you could rake up the leaves and compost or stack for leaf mould, just as a matter of hygiene.

 

There are no greenfly to be seen now. And I dont recall seeing any before ???

 

In that case a better photo, close up and in focus of the marks on the top and bottom of the leaf.
Soon as I try to zoom in or magnify the picture any definition goes.
Personally I still wouldn't spray with anything, the season is just about over and their job is done.