Pear (conference) leaf problem

Question

I have two pear trees probably 20 years old. They have a rust colour spot one side of leaf a swelling growth on the other side nasty . What is the problem
what action is required please.

Answer 1

Here's an article that will help you identify what's going on:
https://www.gardeningknowhow.com/edible/fruits/pear/pear-tree-diseases.htm