the better of this poisonous, yet aesthetically pleasing evergreen, yellow leaves and the decline of the plant might be an unpleasant consequence. (See References 1) Leaf Scorch Disease Leaf scorch is a disease that's caused by the bacteria Xylella fastidiosa. Mainly found in California, this disease is spread from infected plants to health ones by 1/2-inch-long insects known as glassy-winged sharpshooters. When an oleander is infected, the transportation of nutrients and water from the roots to