Oak Tree Dripping Sap? It's Honeydew from Aphids or Scale

Sticky Sap on Your Car and Deck? Blame Insects, Not the Tree

Clear, sticky droplets falling from an oak tree are usually honeydew excreted by aphids or soft scale insects feeding on leaves and twigs. The tree itself is not "bleeding" sap. Honeydew attracts ants, flies, and wasps, and promotes black sooty mold on surfaces below.

Identify the Culprit

• Aphids: Small, soft-bodied, often clustered on new growth or leaf undersides.
• Soft scales: Bump-like, attached to twigs and branches; less mobile.

Control Options

1. Systemic Insecticides (Best for Large Trees)

• Imidacloprid (e.g., Bayer Advanced Tree & Shrub) applied as a soil drench in spring. Taken up by roots, protects canopy for months.
• Dinotefuran (Spectracide Systemic) – faster uptake.
• Acephate (Orthene) – also has contact activity.

2. Contact Sprays (If Canopy Is Reachable)

• Horticultural oil, insecticidal soap, neem oil – thorough coverage needed.
• Pyrethroids (bifenthrin, cyfluthrin) – effective but can harm beneficials.

3. Conserve Beneficial Insects

• Lady beetles, lacewings, parasitic wasps naturally control aphids.
• Avoid spraying when pollinators are active.
• Control ants (which protect aphids) with sticky bands or baits.

Sooty Mold

Once insects are controlled, honeydew stops, and sooty mold weathers away. Wash surfaces with mild detergent if needed.

For a 100-year-old oak, soil-applied systemic treatment is the most practical and effective approach.