Tree disease: advice needed

I think i'm in the right bit.... hello from a new gardener. I've taken the role over from my mum who cant do it anymore due to ill health but I need some advice. She has 3 chinese pear trees that need a little attention. Soil type = clay / free draining.

The leaves on the smallest tree (approx 6' tall) are all shrivalled, dark green with orangy red blotches all over the shop. I noticed a few small blck insects on it so I sprayed it with a general bug killer and long shoots have battled thier way thru the manky leaves on small, fresh branches. This happened to the tallest tree (8') a couple of years ago..... but I pulled ALL the leaves off carefully and within 4 months, good healthy foliage grew back but its just started doing it again. The 3rd tree is going the same way.

Whats happening?????

 

Hi gfrg welcome to the forum, sounds like Rust this link has some advice.
http://www.rhs.org.uk/advice/profiles1001/pear_rust.asp

 

Hey Walnut. Thanks for the info. I was halfway there already by pulling the leaves off! Not bad for a first effort but will persist with this for as long as poss.

Thanks!!!