Answer: How about covering the tree with bird netting? You'll have to secure it around the trunk so the squirrels can't get in. That's the only thing I can think of that won't affect fruit quality. Depending on how low the lowest branches are, you could wrap a wide metal band around the trunk, just as the fruit is ripening. That would prohibit squirrels from climbing the trunk. If the lowest branches are within squirrel jumping distance--or if there are other trees around that the squirrels could jump from, it wouldn't help. I'd try the netting.
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