Answer: Sudden dieback of maples is generally associated with a vascular problem such as root rot or Verticillium wilt. Root rots, obviously, occur if the soil drains poorly and excessive amounts of water from the hose or natural rainfall have made the soil soggy for extended periods of time.
If the dead leaves hang on the tree, Verticillium wilt is certainly a possiblity. To confirm, cut one of the branches and look for dark streaks or bands following the grain of the wood. (This may be absent in the earliest stages of infection, but streaking usually shows up over time.)
Don't do anything drastic at this point. The symptoms might be stress related and the tree may recover, sending out new growth in the spring. On the other hand, a diseased tree will continue to decline and you'll notice stems and branches dry up as they take on a wilted, wrinkled appearance.
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