A sick pear tree

 I'm sorry the pictures aren't that clear. The leaves when they first appeared looked really healthy, then they started to curl and wilt. I have sprayed the tree with Provado the ultimate bug killer thinking it might be leaf midge (I've been scouring the internet for possible causes!) but it's not helped. There is no other visible sign like mildew or stickiness. Can someone help please as I have other fruit trees in pots and am afraid that this may spread.