Holly Hedge Sooty Mold: Aphids on North Side

The black, soot-like coating on your mature holly hedge's lower north-side leaves is sooty mold from aphid honeydew. North side = shadier, cooler, higher humidity = ideal for aphids and mold.

Why North Side?

• Aphids prefer tender, shaded growth.
• Honeydew accumulates where rain doesn't wash it off.
• Sooty mold thrives in humid, low-light conditions.

Control

1. Systemic soil drench (imidacloprid) in early spring—best for large hedges.
2. Horticultural oil spray (dormant or summer) for thorough coverage.
3. Insecticidal soap if accessible (large hedge = hard to spray well).

Key Points

• Power washing removes some mold but not the insects—returns fast.
• Leaves not yellowing/dropping = mold is cosmetic, not killing leaves.
• New growth green = control working.

Treat the aphids; the black coating will weather away. Systemic is most practical for a 6-ft hedge.