dieback

Noun

1. 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...
2. 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).