disease

(noun): An abnormal condition of a human, animal or plant that causes discomfort or dysfunction; distinct from injury insofar as the latter is usually instantaneously acquired.
(noun): (by extension) Any abnormal or harmful condition, as of society, people's attitudes, way of living etc.
(noun): Lack of ease; uneasiness; trouble; vexation; disquiet.
(verb): To cause unease; to annoy, irritate.
(verb): To infect with a disease.

The tomato plants had some kind of disease that left their leaves splotchy and fruit withered.