The Facts About Bacterial Leaf Scorch
At first glance, browning tree leaves during warmer months might seem to be a symptom of drought stress. Look closer, because it could be something much worse: bacterial leaf scorch (BLS).
An incurable vascular disease, BLS is chronic, progressive and can be fatal to trees. In Georgia, BLS is most frequently found in red oak trees, but can infect almost all native oak varieties, as well as other trees including pecan, sycamore, red maple, and others.
The following are four of the key facts to keep in mind regarding BLS.
Fact 1: It’s Caused by a Microscopic Plumbing Blockage
According to the Penn State Extension, BLS is caused by a specific bacterium that is spread by certain insects, who use their piercing mouths to feed on trees. If roots of a diseased tree naturally fuse or graft with those of a neighboring tree, BLS can also spread underground.
Once inside the tree’s water-conducting tissue, the bacterium multiplies through the vascular system. The result is something akin to a clogged sink. The bacterium blocks the pathways that transport water from the tree’s roots to its leaves.
Fact 2: Symptoms Peak in Late Summer and Progress Annually
While tree leaves may look perfectly fine once spring has sprung, things can go south by summer. Symptoms typically materialize late July through September. Keep an eye out for scorched leaves, which can appear yellowed or browned, a telltale sign of BLS. The University of Maryland Extension explains that depending on the species, scorched leaves sometimes have a yellow halo around them. Premature leaf drop can be another signal of BLS. Symptoms first appear on lower branches and on the older interior leaves of the tree and will occur annually, eventually finding their way through the top of the tree.
Fact 3: BLS is Incurable but Manageable
While BLS remains incurable, the disease spreads slowly and proper management can help extend the life of the tree. The Virginia Cooperative Extension reminds us that injecting antibiotics in trees with BLS can delay the progression of disease. However, this approach can be costly and compromise the tree, making it susceptible to wood decay fungi. Minimizing stress factors and keeping a BLS-infected tree as healthy as possible allows it the opportunity to better withstand the progressive effects of the disease. Be sure to water the ill tree during hot and dry weather spells and during periods of drought. Additionally, proper mulching can assist a tree in avoiding water stress.
Fact 4: Professional Guidance is Essential
Are you unable to decide if a tree is diseased or simply thirsty? It’s best not to guess. Reach for a professional to diagnose your tree and guide you through the appropriate solution.
Premier Tree Solutions is an expert in assessing BLS. Call 404-252-6448 or schedule a complimentary assessment online.
Q&A Recap
What Is Bacterial Leaf Scorch (BLS)?
BLS is a chronic, fatal plant disease caused by a certain bacterium that multiplies inside a tree’s water-conducting tissue, creating blockages that prevent water from reaching the leaves.
What Are the Main Symptoms of BLS?
The most common signs include leaf yellowing or browning (often separated from green tissue by a yellow halo), premature leaf drop, and dieback that begins on lower, older branches in late summer (July through September) and recurs annually.
Can BLS Be Cured?
No, BLS is incurable. However, you can manage the disease and extend the tree’s lifespan by reducing environmental stress through supplemental watering during hot weather or drought and proper mulching.
How Does BLS Spread Between Trees?
BLS is spread above ground by sap-feeding insects with piercing mouthparts and underground through natural root fusion or grafts between neighboring trees.







