Answer: Cut off one of the dead branches and look for an olive-green streak within the wood. Hope you don't find any! Maples are susceptible to verticillium wilt and one of the signs is an olive-green (almost black) discoloration running the length of the wood. Once the disease becomes established, it's hard to control. If you do not see any signs of verticillium, the dieback might just be weather related. I would prune the dead branches off and wait for your maple to replace them. Good luck with your maple.
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