What is Oleander Blight?
Oleanders are evergreen shrubs capable of living in the harsh desert environment. Oleanders are popular due to their ability to produce vibrant, brightly colored flowers in the summer months. However, they can fall victim to bacterial blight (also known as leaf scorch). The disease often presents as black or brown spots on the leaves. The bacteria is most often spread by rain and high moisture environments. Spray treatments are generally uneffective in removing the disease.
Managing the Disease
There is no known cure for Oleander blight. Pruning out the part of the plant showing symptoms may improve the physical appearance of the Oleander tree or shrub but will not save the plant.
The bacterial disease is limited to the xylem and can be spread from plant to plant by xylem-feeding insects such as the glassy-winged sharpshooter. Because of the year-round abundance of the glassy-winged sharpshooter, insecticides available on
the market are not effective in stopping the spread of the disease. The best management is early removal of plants infected with the Oleander blight bacteria to reduce the chance of it spreading.
Controlling Oleander Blight
1. Prune branches showing symptoms of Oleander blight with pruning shears. These shears should be cleaned with a diluted bleach solution between cuts to prevent further spread.
2. Water plants directly into the soil beneath the plant. Avoid watering the foliage, as wet leaves and flowers can cause blight to thrive.
3. Fertilize conservatively. Over-fertilizing creates an environment conducive to blight.
4. Remove Oleanders with canker growths on the trunk or that have damage over the majority of the plant. These shrubs are unlikely to recover and could spread the bacteria to other plants.