A client from northern Palm Beach County requested a site visit in order to diagnose the problem with declining Oleanders in a very large golf course community.
The symptoms reported were marginal yellowing of the leaves, followed by leaf scorching, then die-back of individual leaves and branches. The following are photos from the site:
It was determined that the disorder is Oleander Leaf Scorch (OLS), which is caused by the bacteria Xylella fastidiosa. OLS tends to mimic salt injury or severe water stress because it clogs the xylem (the tissues that transport water throughout the plant). You’ll want to pay close attention if you are managing Oleanders that begin to exhibit these symptoms. On this property, as with most cases of OLS, the first signs showed up on a singular terminal branch first. Eventually more of the canopy becomes infected.
The Xylella bacterium is spread by pruning tools and insects that feed on the xylem of the plant, including sharpshooter leafhoppers and spittlebugs. There isn’t a “cure” for OLS, but the disease can be managed. As soon as symptoms are recognized, infected shoots should be removed at two or three feet below the symptoms. Pruning tools should be sterilized between plants, using a bleach solution. If a plant becomes completely infected, it should be removed completely. Make sure to protect Oleanders from other stresses while managing OLS. The goal of managing this disease is to minimize the spread to other parts of the plant and to other plants.
The following documents provide further information on Oleander Leaf Scorch:
UF/IFAS: Nerium oleander: Oleander [publication ENH 571] by Edward F. Gilman and Dennis G. Watson
UF / IFAS Oleander: Nerium oleander by Juanita Popenoe
IFAS Palm Beach Extension: Environmental Horticulture 