Best Management Practices (BMP) Guide for Wetwood (Slime Flux) in Oaks,
1. Identification
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Symptoms: Dark streaks on bark, oozing liquid (foamy, slimy, or crusty when dried).
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Common in stressed oaks, elms, cottonwoods.
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Not typically fatal but can weaken the tree over time.
2. Causes
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Bacteria ferment sap inside the heartwood.
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Internal gas pressure forces sap out through cracks or wounds.
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Hot/dry conditions (like San Angelo summers) stress the tree, making symptoms worse.
3. Management Practices
A. Tree Health Care
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Watering: Deep soak every 10–14 days in summer if no rain. Wetwood trees benefit from consistent soil moisture.
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Mulch: Apply 2–3 inches of wood chips around base (keep 3–4 inches away from trunk).
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Fertilization: Apply a balanced slow-release fertilizer in spring to improve vigor.
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Pruning: Remove only deadwood. Never prune during active slime flux exudation (it spreads bacteria).
B. Wound Care
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Do not seal wounds with paint or tar. This traps bacteria and moisture.
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Let the wound breathe and dry naturally.
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If bark is loose, carefully trim away only dead, detached bark to allow better air circulation.
C. Sanitation
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Wash away heavy slime with water if it attracts insects.
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Disinfect tools with bleach solution (10%) after pruning nearby trees.
4. Monitoring
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Watch for canopy dieback, thinning leaves, or branch die-off.
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If >30% of the canopy declines, consult a certified arborist for potential removal.
5. Prevention
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Avoid mechanical injury (string trimmers, lawnmowers, vehicles).
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Don’t overwater or allow standing water near the root zone.
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Keep grass competition down around the tree base.
Key Point for San Angelo: Wetwood is more a symptom of stress than the root problem. The goal is to reduce stress so the tree can live with it.
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