Curved leaves on currant plant

Hi all,

This year I have decided to plant some currants, gooseberries and blueberries. One of the currant plant has the top leaves all curled up with bunch of ants living in it. Question is, did ants made the leaves curl or is there another cause?

Thanks a lot for the replies,
David

 

Greenfly made the leaves curl. The ants are “milking” the greenfly.