Blight

Blight is a general term for plant diseases that cause rapid, conspicuous damage to plant tissues. Blights are characterized by sudden and severe browning and death of leaves, shoots, flowers, or entire branches, giving affected plants a scorched or burned appearance. The term is descriptive rather than specific to any single pathogen.

Several devastating tree diseases are classified as blights. Fire blight, caused by the bacterium Erwinia amylovora, attacks apple, pear, and related species, causing shoots to wilt and blacken as if burned. Chestnut blight, caused by the fungus Cryphonectria parasitica, virtually eliminated the American chestnut from its native range in the early 1900s. Boxwood blight, sudden oak death, and various needle blights of conifers continue to cause significant damage to forest and landscape trees.

The speed of blight progression often distinguishes it from other disease types. Environmental conditions that favor the pathogen can lead to explosive epidemics. Fire blight, for instance, can spread rapidly during warm, wet spring weather, moving from blossoms through branches and into the main scaffold in a matter of days. Early detection and prompt removal of infected tissue are critical management responses.