defoliation (n.)

1650s, "loss of leaves," noun of action from past-participle stem of Late Latin defoliare "shed leaves," from de (see de-) + folium "leaf" (from PIE root *bhel- (3) "to thrive, bloom"). Often especially of the fall of leaves in autumn. Meaning "deliberate destruction of foliage" (for military purposes) is from 1964.