blight

Any of a number of plant diseases caused mainly by parasitic species of fungus, which produce a whitish appearance on leaf and stem surfaces; for example, potato blight Phytophthora infestans. General damage caused by aphids or pollution is sometimes known as blight.

In 1998 a new virulent strain of P. infestans, US-8, was decimating potato and tomato crops throughout the USA and eastern Canada, proving to be resistant to previously effective fungicides.