Sticky Residue on Leaves or Cars Under Trees
Quick Navigation
What This Symptom Usually Means
Sticky residue on leaves, cars, decks, and surfaces under trees is honeydew — the sugary excrement of sap-sucking insects. It is not tree sap. The most common culprits are aphids, scale insects, whiteflies, and leafhoppers. These insects pierce leaves or bark and feed on the tree's phloem sap, excreting the excess sugar as honeydew. The honeydew then drips onto everything below and is colonized by black sooty mold fungus. While honeydew itself does not directly harm the tree, heavy insect infestations can weaken it, and the resulting mess is a major nuisance.
Most Likely Causes
Aphids
Tiny soft-bodied insects in dense colonies on the undersides of leaves and new growth. Many species — green, black, brown, or pink. Produce enormous quantities of honeydew.
Soft scale insects
Small, immobile, dome-shaped insects on branches and leaf veins. Brown, tan, or white. Heavy scale infestations produce copious honeydew.
Whiteflies
Tiny white flying insects on leaf undersides. Flutter up in a cloud when the branch is disturbed. Common on ornamental trees in warmer climates.
Leafhoppers
Small, wedge-shaped insects that jump when disturbed. Feed on leaf undersides and produce honeydew. Many species affect trees.
Mealybugs
White, waxy, cottony-looking insects in branch crotches and on bark. Produce honeydew and are often tended by ants.
Trees Commonly Affected
Linden
Notorious for aphid honeydew — a major nuisance tree for parking areas
Maple
Cottony maple scale and aphids cause heavy honeydew production
Oak
Kermes scale and various aphids produce honeydew
Tulip Poplar
Tulip tree scale produces extreme honeydew — avoid planting near parking
Elm
European elm scale causes heavy honeydew and branch dieback
Crape Myrtle
Crape myrtle bark scale produces heavy honeydew in the Southeast
How Urgent Is This?
⚠ Moderate Urgency
Moderate. Honeydew is primarily a nuisance, but heavy infestations of sap-sucking insects can weaken trees over time, especially if they occur year after year. The bigger concern is often the practical impact — sticky cars, stained surfaces, and black sooty mold on everything under the tree.
What You Can Do Right Now
- Identify the insect: examine leaf undersides for aphids, branches for scale, and disturb foliage to check for whiteflies.
- Spray aphids off small trees with a strong jet of water from a hose — this is surprisingly effective.
- Encourage natural predators: ladybugs, lacewings, and parasitic wasps eat enormous numbers of aphids and scale.
- Avoid excessive nitrogen fertilization — it promotes the succulent new growth that aphids prefer.
- For heavy scale infestations, apply horticultural oil spray during the dormant season to smother overwintering stages.
- Accept that some honeydew is normal — trees support insect food webs, and minor aphid populations are part of a healthy ecosystem.
When to Call a Certified Arborist
Contact a certified arborist if any of these apply:
- ✓Heavy honeydew is accompanied by branch dieback or canopy thinning
- ✓Scale insects are covering major branches and causing decline
- ✓The tree is too large to treat yourself
- ✓You need systemic insecticide treatment for a severe infestation
- ✓You want help selecting a replacement tree that is less prone to honeydew issues
State & Regional Differences
Midwest
Linden aphids and cottony maple scale are the most common honeydew sources. Spotted lanternfly is arriving in some areas and produces copious honeydew.
Southeast
Crape myrtle bark scale (invasive from Asia) is spreading rapidly and produces extreme honeydew. Scale insects are active year-round in warm climates.
West
Whiteflies are more common in warm western climates. Giant bark aphid on sycamores produces dramatic honeydew in California.
Northeast
Spotted lanternfly is a major emerging pest producing heavy honeydew on ailanthus, maples, and many other hosts. Report sightings to your state.
Frequently Asked Questions
Is the sticky stuff from trees harmful?
Will the sticky residue damage my car paint?
Related Symptoms
Not Sure What's Wrong?
Use our diagnostic tools to identify the problem and get personalized treatment recommendations.