Bacterial leaf scorch

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]

Bacterial leaf scorch
Large pin oak (Quercus palustris) stricken with bacterial leaf scorch during leaf-out
Common names	BLS
Causal agents	Xylella fastidiosa
Hosts	trees and crops
Vectors	leafhoppers

Hosts

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.^[2]

• Xylella fastidiosa is known to cause BLS in a very wide range of plants. Each of its subspecies has have a different host range.^[2]
  • The multiplex subspecies causes BLS of pecans.
• Bacterial spot of peppers and tomatoes is caused by the bacteria Xanthomonas campestris pv. vesicatoria, which has since been divided into four pathovars in three species.^[3]
• Bacterial spot of peaches is caused by the bacteria Xanthomonas arboricola pv. pruni. It also infects almonds.^[4] Spots may form on the leaves and they can be mistaken for peach scab, which is caused by a fungus.

Symptoms

An irregular browning leaf margin which may or may not be bordered by a pale halo.^[5]

Pin oak leaves with symptoms of bacterial leaf scorch

Symptoms re-occur every year, spreading throughout the tree crown, eventually killing the host plant.^[5]

Vectors

Xylem-feeding leafhoppers can transmit the disease bacteria.^[5] In general, any xylem-feeding insect can transmit the disease.^[6]

Treatment

There are no known effective treatments for BLS, consequently, removal of affected plants is recommended.^[5]

See also

• Fertilizer burn
• Leaf scorch