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Beech Leaf Disease Update December 2025

December 31, 2025

Science-Based Protection for Your Beech Trees from Certified Arborists and Plant Biologists

Beech leaf disease is killing trees across southeastern Pennsylvania. American beech, European beech, copper beech, weeping beech—all are susceptible, but damage in our area to American beech is astounding. Saplings can die within two years. Mature trees decline over seven to ten years. But there is now an effective treatment, and Burkholder Plant Health Care has the scientific expertise to deliver it.

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Understanding Beech Leaf Disease

Beech leaf disease is caused by Litylenchus crenatae mccannii, a microscopic foliar nematode first identified in Ohio in 2012. The disease has since spread to all 67 Pennsylvania counties and continues to intensify in severity.

The nematodes inhabit leaf buds and feed on developing tissue, causing characteristic symptoms:

  • Dark green banding between leaf veins, most visible when looking up through the canopy
  • Leaves becoming thick, leathery, and distorted
  • Premature leaf drop and reduced bud production
  • Progressive canopy thinning and branch dieback
  • Thin, gray, sickly-looking trees
  • Tree death, potentially within a decade for mature specimens
beech leaves with dark banding that indicates beech leaf disease (BLD) - Burkholder PHC

Effective Treatment Is Now Available

Recent peer-reviewed research has confirmed that thiabendazole (delivered via root-flare injection) significantly reduces nematode populations and improves tree health. Published trials demonstrated 70–99% reduction in nematode counts in treated trees, with visible symptom improvement within one growing season.

Thiabendazole (the active ingredient in Arbotect 20-S) has been used in arboriculture for decades to manage Dutch elm disease and sycamore anthracnose. Its nematicidal properties—disrupting cell division in these parasites—make it effective against the beech leaf disease nematode. One treatment provides approximately two seasons of protection.

Phosphite Treatments: A Complementary Approach

Potassium phosphite offers another tool for managing beech leaf disease, particularly for smaller trees or as part of an integrated management program. Phosphites work differently than thiabendazole—rather than directly killing nematodes, they stimulate the tree’s natural defense responses and may also inhibit nematode activity within leaf tissue.

Phosphites can be delivered through multiple methods. Trunk microinjection using Phospho-Jet provides systemic distribution similar to thiabendazole macroinjection, but uses less material and allows injection sites to be plugged. Soil drenches and basal bark applications offer less invasive alternatives. Long-term trials in Ohio have demonstrated that phosphite soil drenches improved health and reduced beech leaf disease symptoms in smaller beech trees (2–4 inch DBH) over five years of treatment. More recently, arborists have reported success using phosphite as a basal bark drench applied twice yearly, with complete symptom suppression even in larger trees surrounded by infected neighbors.

Phosphite treatments are particularly valuable because they offer flexible delivery options, can be applied to smaller trees that aren’t candidates for macroinjection, and are accessible to homeowners as a supplement to injections. We can help you determine which approach—thiabendazole macroinjection, phosphite microinjection, soil drench, bark application, or a combination—is most appropriate for your trees.

When to Treat for Beech Leaf Disease

Optimal timing: After full leaf expansion (typically June) but before nematodes migrate from leaves to buds in late summer. In southeastern Pennsylvania, treatments are most effective when applied in June through early August.

Why Choose Burkholder Plant Health Care?

We are not a general landscaping company that added tree injections to a service menu. Burkholder Plant Health Care was founded on the principles of integrated pest management and staffed with credentialed scientists who understand plant pathology, pest biology, and the research behind effective treatments.

Our Scientific Credentials

  • ISA Certified Arborists with decades of combined experience in plant health care
  • Published research scientists: Our plant health care team has authored and co-authored over 80 peer-reviewed and extension publications on integrated pest management and tree health
  • USDA research background: Extensive work with the USDA Agricultural Research Service and cooperating universities developing biologically-based pest management techniques
  • University training in entomology, agroecology and horticulture from programs including University of Massachusetts, Penn State, and Temple University
  • 100% PA licensed commercial applicators meeting all state regulatory requirements
  • Active research: We develop and conduct our own collaborative field trials and stay current with emerging treatment approaches

When you work with Burkholder, you’re working with plant biologists who can explain why a treatment works, not just applicators following a protocol.

What to Expect

Initial Consultation

We assess your trees’ current condition, disease severity, and overall health. Not every tree is a good candidate for treatment—trees with severe, multi-year damage may be too compromised to recover. We’ll give you an honest evaluation.

Treatment

Root-flare injections are performed during the optimal treatment window. The process takes about an hour per tree depending on size. Trees must be at least 5 inches DBH (diameter at breast height) for root-flare treatment, but injections of trees over 10 inches DBH are more practical and cost-effective.

Results

You should expect:

  • Reduced symptom expression in the following growing season
  • Improved canopy density and leaf quality
  • Protection lasting approximately two seasons
  • Ongoing monitoring of tree health by trained professionals
  • Need for retreatment to maintain protection over time

Service Area

We provide beech leaf disease treatment throughout the Philadelphia Main Line and surrounding communities, including Chester County, Montgomery County, Delaware County, and portions of Bucks and Berks counties, along with northern Delaware. Communities served include Ardmore, Berwyn, Bryn Mawr, Chadds Ford, Chester Springs, Devon, Gladwyne, Malvern, Media, Newtown Square, Radnor, Swarthmore, Villanova, Wayne, West Chester, Wilmington, and surrounding areas.

Protect Your Beech Trees

Beech leaf disease is progressing rapidly across our region. Early intervention produces better outcomes. If you have beech trees showing symptoms—or healthy trees you want to protect—contact us for a consultation.

Burkholder Plant Health Care
1595 Paoli Pike (Suite 201), West Chester, PA 19380
484-630-5924

Certified arborists. Published researchers. Plant biologists. Science-based plant health care for the Main Line.

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