White Oak Weeping Sap: Slime Flux Explained

Vertical Crack with Persistent Dampness

A 30-foot white oak has a 5–6 foot vertical crack 10–15 feet up, weeping sap and staying damp even in dry weather. Carpenter ants were present years ago but are gone; the old injury has healed.

Diagnosis: Slime Flux (Wet Wood)

The expert confirms this is slime flux—an external bleeding of sap linked to internal bacterial infection (wet wood). Bacteria enter through wounds, colonize heartwood, produce gas, and force sap out. The sap darkens, becomes frothy, and smells foul due to surface colonization by yeasts and fungi.

Internal Signs

Cross-sections show dark, water-soaked, malodorous wood. High internal pressure from methane, nitrogen, and CO₂ drives the flux.

Control Measures

• Prune declining branches.
• Fertilize to boost vigor and wound closure.
• Do not install drain tubes—they can spread bacteria and create entry points for decay fungi.
• Avoid tree injuries; use clean, sharp pruning tools.
• Reduce moisture stress with proper watering.

Key Insight

There is no cure for slime flux, but good cultural practices can help the tree compartmentalize the issue and maintain health.