Sycamore Disease and Yellow Leaves

The foliage of sycamore trees can turn yellow when infected with bacterial leaf scorch.

Sycamores includes the American sycamore, eastern sycamore, button ball tree and buttonwood. These trees are members of the Plantanaceae family, which are large trees that thrive in medium to wet soils. Sycamore trees are high maintenance and are susceptible to a disease known as bacterial leaf scorch, which is common in sycamores.

Identification

Bacterial leaf scorch or BLS is a common shade-tree disease, often infecting sycamore, sugar maple, red maple, mulberry, American elm and sweet gum trees. BLS also affects several members of the oak family including pin oak, red oak, laurel oak, turkey oak, shingle oak, bur oak and scarlet oak. Xylella fastidiosa bacteria, which is transmitted by insects, causes BLS. According to the U.S. Department of Agriculture, leafhoppers are known to spread the bacteria that causes BLS.

Effects

Sycamore trees infected with BLS have browning of leaf margins, followed by a yellow halo that separates the brown, scorched tissue from the green leaf tissue. Symptoms return each year and spread through the crown of the tree, caused reduced vigor and dieback. As BLS spreads throughout the tree, it causes a slow decline in health and infected trees eventually die.

Cultural Control

There is no cure for BLS, so maintaining the tree by pruning away diseased branches is the best course of action after infection. Pruning diseased trees can prolong the life of the tree and maintain safety from falling branches. Placing mulch around trees and irrigating frequently with can reduce drought stress in sycamore trees with this disease, reducing symptoms.

Chemical Control

While there are no chemical control methods that cure BLS in sycamores, trees often experience a delay in severe symptoms after injections of antibiotics are placed into the trunk of the tree. Treatments must be performed each year during late May or early June to be effective. Sycamore trees that suffer severe symptoms of BLS must be removed to maintain safety.

References

• MOBOT: Plantanus occidentalis
• USDA: Bacterial Leaf Scorch of Shade Trees; Jo-Ann Bentz, et al.