Bacterial Leaf Scorch
Bacterial leaf scorch is caused by a bacterial infection of a tree’s water conducting tissue. The bacteria are vectored by a number of insects. This disease can be very difficult to diagnose; symptoms of bacterial leaf scorch closely resemble those of other vascular diseases, declines, and abiotic stresses such as drought.
Infection is perennial; bacteria are able to survive from year to year in the vascular system. Bacteria interfere with water transport in the xylem, therefore symptoms closely resemble those of drought and other vascular diseases. Leaf margins turn red or yellow; then leaves will wilt and turn brown especially during the summer months. A red or yellow band often separates brown from green tissue. Older leaves are usually scorched first, with symptoms progressing towards shoot tips. Scorched leaves are retained on the tree into the fall.
Trees may have decreased fruit production, delayed bud break, reduced growth, stunting, branch dieback, and eventually death. Leaves usually expand normally each year; then symptoms begin to appear in late spring and progress throughout the summer. Hot droughty weather makes symptoms worse. Symptoms may initially appear in isolated branches or sections of the crown, but eventually spread throughout the tree. Symptoms can fluctuate in severity from year to year.
There are currently no effective treatments for bacterial leaf scorch.