warts on plum leaves

Hello, I was just lloking in the garden and noticed that a plum tree I have has quite a few leaves that i can only describe as 'warty'he affected leaves seem to have depressions on the top side and underneath there are some warty roundish growths which are round the edge of the leaf. I attach a photo but its not brilliant. can anyone tell me what is the problem and how it can be cured? thanks

 

sounds like the damage caused by aphids on early leaves to me - I get it on my greengage. Doesn't look great - but doesn't seem to affect the flowering and fruiting.

 

well after I posted I got one of the leaves to see if there were any insects inside the knobbly bits. I carefully dissected a couple but there was nothing so i guess as you say its some kind of damage but whatever isnt present know!

 

These galls are the plants' reaction to various mites, aphids and flies. The swelling is similar to the swelling we get when bitten or stung. Only in certain cases (like oak apples) are eggs laid and insects living inside the galls. These warty galls on leaves do no harm. Sometimes the galls cause an inbalance in the growth hormones of the trees and then we get bizarre formations of "witches brooms".

 

Thanks both for the info. now I know they are not harmful I will relax a bit.