dieback /ˈdaɪˌbæk/

• 1. 

  N a disease of trees and shrubs characterized by death of the young shoots, which spreads to the larger branches: caused by injury to the roots or attack by bacteria or fungi (植物根部受伤或受细菌、真菌等侵害造成的)顶梢枯死

• 2. 

  V (of plants) to suffer from dieback (植物)顶梢枯死