Bacterial Leaf Scorch

Bacterial leaf scorch causes browning or a scorched appearance on the outer areas of leaves. It is caused by the bacterium Xylella fastidiosa.  

Bacterial leaf scorch is a systemic disease that invades the vascular tissue known as xylem. The xylem is responsible for the transportation of water and nutrients from the root system to the rest of the tree.  

Tree species expected

American sycamore, mulberry, grape, American elm, sweetgum, boxelder, dogwood, red maple, and sugar maple.  

Oak species affected are bur, live, pin, scarlet, shingle, southern red, water, and willow.  

Symptoms 

Bacterial leaf scorch is often mistaken for drought damage due to the browning or “scorched” appearance on the outer areas of the leaves. Some indicators include:  

• Symptoms show mid to late summer,  

• Premature browning of leaves, and 

• Brown leaf tissue may be separated from the healthy green tissue by a thin yellow band.  

The only way to confirm is with a laboratory bioassay test. 

Spread

Leaf scorch is spread by planthopper insects when feeding on infected tissue. The insect families that are known to spread the bacteria are spittlebug (Cercopidae) and leafhoppers (Cicadellidae).  

Treatment and management

There is not an effective cure for bacterial leaf scorch. Infected trees will eventually need to be removed and replaced. However, if only some of the branches are affected, it might be possible to limit the spread by selectively pruning the diseased branches.  

There might be a connection with water stress, therefore, provide supplemental watering during periods of hot, dry weather.