Scale and Sooty Mold on Transplanted Holly: Oil Spray Solution

From Flies to Black Powder

Three hollies transplanted last summer near porch. Black flies swarmed. Now (spring) coated in black powder. Chunk bark mulch used.

Diagnosis

• Black Flies: Adult scale insects mating/laying eggs.
• Black Powder: Sooty mold on honeydew from immature scale.
• Mulch: Not the cause—bark mulch is fine.

Treatment

Spray horticultural oil this spring. Thoroughly coat interior branches where scale feeds and eggs hide. Repeat per label. Oil suffocates scale; mold disappears as food source vanishes.