Weeping Red Oak: Honeydew from Aphids, Not Tree Sap

A 20-year-old red oak in the Bay Area drips sticky droplets year-round (worse this year), coating cars. Owner asks if anything can be done.

Cause

Honeydew from aphids feeding on leaves/twigs. High sugar = sticky.

Systemic soil drench: imidacloprid (Bayer Advanced Tree & Shrub) applied to root zone—best for large trees.
Foliar systemics: acephate (Orthene), dimethoate (Cygon).
Older soil systemic: disulfoton (DiSyston) granules—more toxic.

Treat aphids; dripping stops.

Trees: Oak Tree Weeping Sap: Borer Infestation and Treatment; Controlling Scale Insects on Weeping Willow with Systemic Insecticide; Vein Pocket Gall on Red Oaks: Identification and Low‑Cost Management; Red Oak Distress After Lawn Aeration: Root Damage Likely Cause; Oak Borer Infestation: Assessment and Neighboring Tree Protection; Laurel Oak Dripping Sticky Sap: Scale Insects & Honeydew; Red Oak Losing Limbs in Summer: Drought Stress, Not Borers; Red Oak Aphid Infestation: Systemic Treatment Timing and Pruning Coordination; Decay Fungus Conks on Red Oak: Not an Emergency; Weeping Oak Sap: Aphid Honeydew, Not Tree Sap

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