canker

(kăngˈkər)

1. Ulceration of the mouth and lips.
2. An inflammation or infection of the ear and auditory canal, especially in dogs and cats.
3. A condition in horses similar to but more advanced than thrush.
4. a. A localized diseased or necrotic area on a plant part, especially on a trunk, branch, or twig of a woody plant, usually caused by fungi or bacteria.
   b. Any of several diseases of plants characterized by the presence of such lesions.
5. A source of spreading corruption or decay.

1. To attack or infect with canker.
2. To infect with corruption or decay.