Diagnosing and Managing Slime Flux on Honey Locust Trees

What Is That Dark, Frothy Sap Seeping From Your Tree?

The "root beer" colored, foul-smelling liquid oozing from your honey locust's trunk is classic slime flux (wetwood)—a bacterial infection of the heartwood. Unlike insect borers, this condition produces no visible entry holes; instead, internal gas pressure forces fermented sap through bark fissures and old wounds.

Understanding the Disease Process

Common soil bacteria enter through wounds, pruning cuts, or root injuries. Once established in the heartwood, they ferment wood tissues, producing methane, nitrogen, and carbon dioxide. These gases build pressure (up to 60 psi), forcing dark, frothy, bacteria-laden sap outward. The alkaline flux kills grass and plants beneath the tree.

Recognition Signs

• Dark brown, slimy, foul-smelling ooze from bark cracks or branch crotches
• Light gray/white crust on bark after flux dries
• Internal wood appears water-soaked and dark in cross-section
• Associated with old wounds, included bark, or storm damage

Management Options

No cure exists for established wetwood. However, you can support tree vigor:

• Fertilize with 10-10-10 at 1 lb per inch trunk diameter (scatter to drip line, water in)
• Prune declining branches to reduce weight stress on infected wood
• Avoid wound dressings—they trap moisture and worsen decay
• Do not install drain tubes—outdated practice that spreads bacteria

Long-Term Outlook

Many trees coexist with slime flux for decades. Focus on preventing additional stress: proper watering, mulching, and avoiding root damage. The tree's external sapwood remains functional even as heartwood degrades.