(Wells et al. 1987) is a gram-negative, fastidious, xylem-inhabiting bacterium.
It causes serious diseases in grapevines (Pierces disease), almonds
(Almond leaf scorch), alfalfas (Alfalfa dwarf), and oleanders (Oleander
leaf scorch) in California and numerous other diseases in North and South
America. An epidemic of oleander leaf scorch was first noticed in 1994 in
southern California. It was found that the glassy-winged sharpshooter, Homalodisca
coagulata Say, as well as several other sharpshooters, could transmit
X. fastidiosa from oleander to oleander. Description of almond, oleander,
and other leaf scorch diseases caused by different strains of X. fastidiosa
can be found at the following website: http://www.CNR.Berkeley.EDU/xylella/
Photo: Electron Microscopy Laboratory,
Causative agent of oleander leaf scorch.
Characteristic symptoms: marginal scalloped chlorosis
(yellowing), followed by marginal or tip leaf scorch, then die-back of
twigs and branches. The disease seems to kill oleander within about two
years of the first appearance of symptoms.