Sticky Liquidambar Leaves: Scale Insects, Not Tree Sap

The Real Source of the Mess

Fine, sticky mist coating cars and shoes under liquidambar (sweetgum) trees is honeydew from scale insects, not tree sap. Tree sap exudes in gobs down the trunk; honeydew atomizes into a fine, far-reaching film.

Scale vs. Aphid Identification

• Scales: Immobile, shell-like bumps on twigs/branches (often overlooked).
• Aphids: Mobile, on leaf undersides and new shoots.
• Both suck phloem → secrete honeydew → sooty mold → bee/wasp attraction.

Best Control for Large Trees: Systemic Soil Drench

• Imidacloprid (Bayer Advanced Tree & Shrub) applied to root zone.
• Translocates to foliage/twigs → kills scales/aphids as they feed.
• 2-3 weeks to reach canopy; season-long protection.
• Avoids spray drift, thorough coverage challenges on tall trees.

Why Not Foliar Spray?

Mature liquidambars are too large for effective spray coverage. Systemic treatment is the only practical option for homeowners.

Monitoring

• Check twigs annually for scale buildup.
• Early treatment prevents heavy honeydew/sooty mold seasons.
• Healthy trees (water, mulch, no excess N) resist infestation better.