Bacterial leaf scorch (commonly abbreviated BLS, also called bacterial leaf spot) is a disease state affecting many crops, caused mainly by the xylem-plugging bacterium Xylella fastidiosa.

[1] It can be mistaken for ordinary leaf scorch caused by cultural practices such as over-fertilization.

[1] BLS can be found on a wide variety of hosts, ranging from ornamental trees (elm, maple, oak) and shrubs, to crop species including blueberry and almond.

[citation needed] An irregular browning leaf margin which may or may not be bordered by a pale halo.

[2] Symptoms re-occur every year, spreading throughout the tree crown, eventually killing the host plant.