dieback

The browning and death of a plant shoot starting at the tip, due to either disease or climate conditions.

The National Trust reports that 30,000 ash trees on its land will have been felled this year owing to ash dieback. “Dieback” sounds like a gentle, seasonal withdrawal. In fact, ash dieback is a devastating disease caused by a fungus, Hymenoscyphus fraxineus, likely to have been carried into the UK on imported ash saplings in the early part of this century.

The withering of a plant, especially the cyclical withering in autumn and winter; distal parts die off but core parts stay alive (and semidormant or dormant).