California Oak Wetwood (Slime Flux): Bacterial Ooze, No Cure Needed

California oak has white bubbly foam from trunk bark; one limb has rot. Expert identifies Wetwood (slime flux): bacterial fermentation of sap → gas pressure forces sap out through cracks/wounds. Two types: alcoholic and acidic (vinegar smell). Attracts insects. Discolors bark. Large mature oaks often get it on trunk/flare roots without wounds. Triggered by heat, drought, stress. No treatment—washing trunk with bleach solution (1 pint bleach/gal water) discourages bugs. Maintain vigor, minimize wounds. More harm from “curing” attempts than flux itself. Limb rot: no cure; remove if hazard.

Follow-Up: Scale?

Owner asked if scale. Expert gave scale ID guide: tiny parasitic insects, 7,000 species, 1/16–1/8". Soft scale (waxy) vs. armored scale (hard shell). Mealybugs are scale relatives. Crawlers (newly hatched) are vulnerable stage. Control: dormant oil in late spring, prune early infestations, encourage beneficials (lady beetles, wasps), arborist systemic for large trees. Indoor: rub with alcohol on facial sponge.

Bottom Line

• Wetwood = cosmetic, self-limiting.
• Scale = treat if confirmed.
• Don’t drill, drain, or inject.