Red Oak with Black Residue: Sooty Mold from Aphids/Scale

West Houston red oak has black residue on older leaves and branches. Owner asks for cause.

Diagnosis

Sooty mold on honeydew from aphids or scale insects. Leaves feel sticky.

Late summer: do nothing; leaves fall soon.
Next spring: if sticky leaves reappear, apply systemic imidacloprid (Bayer Advanced) as soil drench.
Foliar sprays (acephate) work but hard on large trees.

Mold doesn't harm tissue; it's cosmetic.

Trees: Gardenia Sooty Mold: Control Aphids, Wash Off Mold; Hundreds of Black Beetles on Young Oak: Identification and Control Options; Sooty Mold on Pecan Leaves: Caused by Insects, Not a Primary Disease; Red Oak Distress After Lawn Aeration: Root Damage Likely Cause; Black Film on Multiple Trees: Sooty Mold from Scale/Aphids; Black Sticky Residue on Patio: Sooty Mold from Aphids or Scale; Aphids or Scale Causing Black Sooty Mold on Oak; Nepenthes Red/Black Leaves in Terrarium: Soil Breakdown and Overwatering; How to Distinguish Red Oak, Black Oak, and Bur Oak; Japanese Maple Leaves Turn Black, Not Red: Environmental Mystery

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