> I took some advice to remove the affected leaves
That was bad advice. You don't need to remove leaves, just spray.
I don't really see wha tyou can do other than cross your fingers and
hope it grows some new leaves to replace those lost. I had a different
problem with a fruit tree that really did require me to remove affected
leaves, and it was most of them. They did grow back.
But yours is a newly planted tree. Usually a bad infestation is a
symptom of an underlying weakness with the tree. If your tree does die,
being a first year tree, I would complain to the supplier, a reputablr
one will give you a replacement, though may have to wait till the
winter. Perhaps not mention the deliberate deleafing.