Spraying at this stage would be a complete waste of time, as the larvae have by now wound themselves up in their leafy cocoons, so the only effective control is to hand-pick them. Look for damaged, curled leaves, leaves/blossom stuck together and dark dots of 'frass' which are the droppings of the grubs. Unfurling the leaves will reveal a sticky web, and eventually a green grub.
After a while it gets easier to spot them, and I removed a large pot-full of dubious, sticky leaves, mostly from apples but one or two from pears. This task will be repeated every day from now on.