Hello TonyO, Welcome to The Gardener's Forum.
The symptoms you described is most likely caused by Verticillium Wilt [Fungi]. It interfers with the
plants vascular system(of phloem and xylem) that transports nutrients, food and water among the
plant's parts. The interference causes foliage to turn yellow or brown and sometimes wilt in scattered portions of the canopy or branches. Shoots and branches wilt and die especially the young
tree. Mature
trees may take many years to die, but may also recover when conditions becomes favorable for the
plant.
The Verticillium Wilt fungus (microsclerotia) is present in the soil. When it is cool and roots are present, microsclerotia germinate and hyphae grow from them. Hyphae infect
plants through the roots, then spread upward in the current year's growth, blocking the ability to transport nutrients and water.
Provide infected maple with proper irrigation, modest amounts of slow-release fertilizer and other appropriate carte to promote new growth and increase their chances of survival.
Prune out dead any dead branch(es).
You can also try solarizing the soil.
(Source: Pests of Landscape
trees and Shrubs, University of California)
For more info see also
Verticillium Wilt
