Oleander (Nerium oleander L.) is an evergreen shrub native to the Mediterranean region and Southeast Asia. Despite being poisonous, it is a popular ornamental plant for use in landscapes, gardens, parks, roadsides and highway medians. Oleander leaf scorch (OLS) is a deadly disease of oleander that was first reported in California in the early 1990s. Since then, OLS has been found across the southern United States and was recently reported in Louisiana.
OLS is a bacterial disease caused by Xylella fastidiosa. Different strains of this bacterium are known to cause several economically important diseases, including Pierce’s disease of grapevine, plum leaf scald and leaf scorch of almond, coffee, pear, pecan, oak and several other landscape trees. The bacterium resides in the xylem vessels (water-conducting channels) of the plant, where it multiplies and blocks these channels and eventually obstructs the flow of water and nutrients within the plant. The bacterium is transmitted and spread by xylem-feeding insects, such as sharp shooters, leaf hoppers or spittle bugs.
See pdf for more detail.
The LSU AgCenter and the LSU College of Agriculture