Black Wet Areas on Oak Trunk: Borer Damage, Not Fatal

Wet, dark streaks on oak trunk = **borer activity** (likely flatheaded or roundheaded borers). They attack **stressed trees**.

Immediate Steps

1. **Spray trunk** (lower 10–16 ft) with **Onyx (bifenthrin) or Merit (imidacloprid)**—kills active borers, prevents new entry.
2. **Fertilize for vigor:** 10-10-10 at 1 lb/inch DBH, **now and spring**. Water in.
3. **Water deeply** during drought.
4. **Mulch** root zone.

Prognosis

• **Few borers = tree survives.** Many borers over years = girdling, death.
• **Healthy trees resist borers** (sap pressure, defensive compounds).
• **Not a death sentence**—but a wake-up call to improve care.