Maple Slime Flux (Wetwood): Oozing, Sour Smell, and Sparse Canopy

The sour-smelling liquid oozing from your 20-year-old maple's trunk, combined with sparse foliage, indicates slime flux (wetwood)—a bacterial infection in the heartwood.

What It Is

• Bacteria enter through wounds (pruning, cracks, frost) and ferment sap.
• Pressure builds, forcing foul-smelling, frothy liquid out through cracks.
• Attracts flies, bees, wasps, butterflies to the sugars.
• Usually not fatal—more a symptom of internal decay than a primary killer.

Management

• No cure. Bacteria are deep inside; antibiotics don't reach them.
• Do not drill drain holes—spreads infection, weakens structure.
• Reduce stress: Water deeply in drought, mulch, avoid wounding.
• Monitor structure: Internal decay may weaken limbs. Have an arborist assess risk if near structures.

Professional Evaluation

Contact Maryland DNR Forest Service for a forester visit. They can assess decay extent and structural stability. The sparse canopy may be from wetwood stress, root issues, or age-related decline.

Many trees live decades with slime flux. Focus on vitality and safety monitoring.