There have been several similar queries recently. The consensus is it is due a combination of lack of water (this or last year), an unseasonably warm early spring followed by late frosts and strong drying winds. All you can do is water deeply (2 buckets, 2-3 times a week) and wait for the tree to shed the damaged leaves and grow new ones. It's not a disease.
A trowel in the hand is worth a thousand lost under a bush.
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