Sooty Mold on China Hollies: Scale Insects and Horticultural Oil Treatment

Black sooty coating on China holly leaves is sooty mold—a fungus growing on honeydew excreted by scale insects. The mold itself doesn't damage the plant; the scales do, by sucking sap and weakening the holly.

Control: spray horticultural oil thoroughly, covering leaf undersides, stems, and branches. Oil suffocates scales. Apply in late winter (dormant rate) or growing season (summer rate per label). The oil also loosens sooty mold, which washes off with rain or a hose spray.

Check for scale: small, immobile bumps on stems and leaf midribs—brown, white, or black depending on species. Ants farming honeydew are a clue. Systemic insecticide (imidacloprid) as a soil drench provides longer control for heavy infestations.

Healthy hollies resist scale better. Ensure proper soil pH (acidic), drainage, and fall fertilization.