Hello
My previously healthy hydrangea bush has developed some sort of problem, see attached pic. The scabs are about 3-5mm long but don't seem like the mealy bug or scales disease I've found info on - can anyone advise what it is & an effective treatment? I've tried spraying it with a non-systemic greenfly & mite spray but it doesn't seem to have helped. It's still flowering ok but a fair few leaves have died.

Thanks in advance.