Jacaranda trees (Jacaranda acutifolia) brighten the landscape in warm, nearly frost-free climates throughout the U.S. where they grow as lawn, patio and roadside trees. In the spring, they produce huge, pyramid-shaped clusters of violet flowers at the tips of branches. In summer, arching branches of fernlike leaves steal the show. Disease seldom bothers these trees, but in the presence of the right insect vectors, bacterial leaf scorch may become a problem. Various strains of Xylella fastidiosa, the bacteria causing the disease, affect more than 100 species of trees and shrubs.
Bacterial leaf scorch affects the tissue within trees and shrubs that conduct water. As a result, the symptoms mimic drought or heat stress. The leaves' edges turn brown. Leaves, branches and twigs die as the disease progresses. Differentiate drought from disease by watering the jacaranda tree. Trees suffering from drought quickly show signs of recovery. The symptoms are most noticeable in late summer and fall.
X. fastidiosa lives in the xylem, the fluid-conducting tissue of a jacaranda tree that lies just beneath the bark. Insects feeding on the xylem spread the disease. The primary bacterial leaf scorch insect vector for is the sharpshooter leafhopper, although other xylem-feeding insects, such as spittlebugs, may also carry the disease. The bacteria reproduce in the insect's mouth, so that once the insect acquires the bacteria it keeps it for life, spreading it from tree to tree as it feeds.
Sharpshooter Leafhopper Identification
Sharpshooter leafhoppers are 1/2-inch, winged insects with triangular-shaped heads. Smoke tree and glassy winged sharpshooters are dark brown on top with lighter-brown undersides. They have light-beige or yellow spots or wavy lines on their heads. Blue-green sharpshooters have greenish bodies dotted with spots and irregular lines. All sharpshooter varieties resist insecticides. Removing their food source is the best control method.
There is no cure for bacterial leaf scorch. You can prolong the tree's life by keeping the soil around the plant moist. However, as long as the tree stands, it is an inoculation source for insects that transmit the disease. Removing and destroying the tree is the best solution. Plant a species that resists bacterial leaf scorch in its place.