Cannot be dabbled
This spell makes the target limb useless. You must state the limb to be affected in the incantation, but you do not need to hit that limb specifically. A withered limb may be healed by use of the Aid skill, the spell heal limb, the healing spell, and other greater magical effects.
Incantation: "By the wicked words, I Wither your (right/left) (arm/leg)."