Chinese Pistache Black Sap: Slime Flux vs. Borer Damage

Symptoms

2–3 yr old Chinese Pistache: black "fluid" (espresso color) oozing lower trunk. Wet, no odor.

Two Main Possibilities

Slime Flux Deep Dive

• Bacterial infection in heartwood → fermentation → gas pressure → sap forced out cracks/wounds.
• Dark brown, frothy, foul-smelling when colonized by yeasts.
• Alkaline sap kills grass/plants below.
• Internal wood: dark, water-soaked, malodorous.
• Bacteria enter via wounds, pruning, insects, roots.
• No cure. Drain tubes outdated (spread bacteria, invite decay fungi).
• Management: vigor (water, fertilize), avoid wounds, proper pruning.

Borer Treatment (If Confirmed)

• Spray trunk with Merit (imidacloprid) now + April.
• Fertilize 10-10-10 at 1 lb/inch trunk diameter.
• Borers attack stressed trees—vigor is best prevention.

Decision Tree

1. Smell it up close. Foul = slime flux.
2. Inspect for holes/frass. Present = borer.
3. No smell, no holes = likely slime flux (early stage) or abiotic sap flow.
4. Either way: fertilize, water, protect trunk.