My 10-year-old-ish pear tree has gone wonky again. A month ago it looked beautiful with fresh green leaves but suddenly the leaves develop rust-coloured patches all over them and fall off. The patches are smooth on both sides so I don't think its scab, and theres no sign of insects. There is actually new growth on the ends of some of the branches. Last year I wondered if it was too dry but that can't be the case this year.
All help gratefully received!