Black Sticky Residue on Patio: Sooty Mold from Aphids or Scale

That Black Film Is Fungus Growing on Insect Excrement

Sooty mold is a black fungus that grows on honeydew—a sugary liquid excreted by sap-sucking insects (aphids, scale, whiteflies). The sticky residue on furniture, roof, and plants confirms honeydew.

Source: Likely the Oak

Large oaks commonly host scale or aphid populations high in the canopy. Honeydew rains down, coating everything below.

Control the Insects, Eliminate the Mold

• Soil-applied systemic: Imidacloprid (Bayer Advanced Tree & Shrub Insect Control) – homeowner-friendly, applied to soil, protects canopy for months.
• Foliar spray (pro only): Acephate (Orthene) – requires high-pressure equipment for large trees.

Once insects are controlled, honeydew stops, and sooty mold weathers away naturally. No fungicide needed.