Photo: American Phytopathological Society
A high number of pin and other oak trees in Moultrie County have been diagnosed with Bacterial Leaf Scorch. Given the close proximity to us, we like to pay attention to what is happening to our neighbors.
Bacterial leaf scorch is caused by the bacterium Xylella fastidosa and is spread by xylem-feeding leafhoppers, treehoppers and spittle bugs. There are a wide array of susceptible hosts, including sycamore, red maple, sugar maple, sweetgum, dogwood, several species of oak and agricultural crops such as peach and pear trees and grapes.
This disease shows symptoms in late summer and fall, with leaves become prematurely brown; and generally starting in just one limb or region of the tree. Infected trees leaf-out normally the following year, with leaves on a few more branches turning prematurely brown in late summer. Symptoms become progressively more widespread over a period of 5 to 10 years, until the entire tree turns brown prematurely. The lack of green, chlorophyll producing leaves year after year leads to twig, branch and limb death due to continual defoliation.
Unfortunately, there is no cure for this disease. It is chronic and eventually fatal for the tree. Studies have shown that yearly injections of antibiotics only slow the progression of the disease, and can actually lead to more damage by creating new entry points for insects or pathogens at the injection site. The good news…? Thankfully, it doesn't seem to readily spread to nearby trees.
Sometimes this disease can be confused with leaf scorch, which is caused by environmental factors such as drought conditions and hot, windy weather. Leaf scorch is generally not fatal and watering during extremely dry weather will restore its vigor.
Visual clues can sometimes help you tell the difference between leaf scorch and bacterial leaf scorch.
Bacterial Leaf Scorch: Leaves from infected trees often display a yellow or red brown border between the dead tissue and green tissue on the leaves.A single limb may be infected first, or all of the lowers limbs on pin oaks.
Leaf Scorch: Leaves from affected trees will have more uniform browning, likely starting around perimeter of leaves and leave tips. Browning of leaves will occur over a large portion of the tree all at the same time.
For positive identification, send sample of several infected leaves to the U of I Plant Clinic for diagnosis. It only costs $15 and postage; a heck of a deal for peace of mind or the time to save for tree removal and purchase of replacement.