When your once-mighty oak starts showing crispy, scorched leaf edges in late summer, it’s not just heat or drought and could be something far more serious. We’re talking about Bacterial Leaf Scorch (BLS), a chronic, often fatal tree disease that’s becoming more common in eastern Pennsylvania. In fact, about 25% of the oaks in the Doylestown, PA area are infected.
In this blog, we break down what Bacterial Leaf Scorch is, how to spot it, and what you can do to protect your oak trees. For homeowners in the Bucks and Montgomery County areas, Keystone Tree Experts bring over 57 years of local horticultural experience and a team of six ISA-certified arborists who can help you fight back against diseases and protect your trees.
Continue reading to learn more about Bacterial Leaf Scorch in oak trees and contact Keystone Tree Experts to speak with our Certified Arborists and technicians about your tree problems in Bucks County and Montgomery County, PA.
What is Bacterial Leaf Scorch?
BLS is a chronic disease caused by the bacterium Xylella fastidiosa, which colonizes the xylem, the tree’s water-conducting vessels, essentially clogging the tree’s circulatory system. This blockage prevents water and nutrients from reaching the leaves, which leads to the characteristic browning or “scorch” around leaf margins.
The disease is spread by common insect vectors like leafhoppers, spittlebugs, and treehoppers, which transfer the bacteria from infected plants to healthy ones, even across different species in your landscape.
Which Trees Are Most Vulnerable to BLS?
Not all oaks are equally affected by Bacterial Leaf Scorch. In Bucks and Montgomery Counties, the disease hits hardest among:
- Red Oaks (Quercus rubra): Highly susceptible and often show fast progression of symptoms.
- Pin Oaks (Quercus palustris): A common landscape tree in PA suburbs and one of the first to show scorching.
- Bur Oaks (Quercus macrocarpa): Increasing reports of infection, particularly in urban landscapes.
- Scarlet Oaks ( Q. coccinea): Known carriers in Eastern states.
These trees are high-value specimens, which makes early intervention even more important.
Bacterial Leaf Scorch Symptoms to Watch For
The ISA-certified arborists and technicians at Keystone Tree Experts say to keep an eye out for these symptoms of Bacterial Leaf Scorch on your oak trees:
- Scorched leaf margins with a yellow or reddish-brown halo in the late summer
- Symptoms start on older leaves, typically mid-to-lower branches
- Gradual progression year-over-year
- Eventual branch dieback and overall decline of the tree
When to Test for Bacterial Leaf Scorch
The ideal time to test is late summer into early fall, when bacterial activity is at its peak and symptoms are easiest to identify.
How to Manage Bacterial Leaf Scorch
Bacterial Leaf Scorch in oak trees sadly cannot be cured, but it can be managed with proactive, professional tree care. Here’s how the team of ISA certified arborists in Bucks County help with tree disease control:
Our BLS Treatment Program
- Boost overall tree health: Use proper mulching, avoid over-fertilizing, and water during dry spells
- Replace when necessary: Severely affected trees will need removal and replacement with resistant species, not oaks
- Antibiotic Trunk Injections: While not a cure, our injection program every other year has been shown to suppress symptoms and extend the lifespan of infected oak trees.
We are currently using a mixture of an antibiotic and another product. This combination, applied via a specialized trunk injection, strengthens the tree’s defenses and helps it better withstand the disease’s effects.
Insecticide sprays are ineffective for stopping the disease, so don’t waste time or money chasing vector control.
What Bacterial Leaf Scorch Looks Like
Get a Professional Diagnosis from our ISA Certified Arborists
Confusing Bacterial Leaf Scorch with drought, oak wilt, or nutrient deficiencies can lead to mismanagement. Our team of ISA Certified Arborists and technicians at Keystone Tree Experts knows how to identify and treat Bacterial Leaf Scorch specifically for Pennsylvania’s oak species and climate, helping you improve the look and health of your property’s landscape.
If you suspect your tree might be infected, don’t delay. Contact Keystone Tree Experts today for tree disease control services in Bucks County and Montgomery County, PA today.
