How to Get Rid of Aphids on Trees (Without Killing Everything Else)

You walk outside one morning and your crape myrtle leaves are sticky. The car parked under the maple is coated in something shiny. There’s black mold growing on the patio furniture. Look up. Aphids.

Those tiny pear-shaped insects multiply so fast that a single female can produce billions of descendants in one season without ever mating. But here’s what most homeowners don’t know: the best response to aphids is usually doing nothing. Most established plants can tolerate aphid feeding and will outgrow any damage.

The trick is knowing when to wait, when to act, and how to act without making the problem worse. That last part trips up more gardeners than the aphids themselves.

How aphids work (and why they’re so hard to stop)

Aphids reproduce through a process called parthenogenesis. Females give birth to live female clones without mating. Each newborn starts feeding immediately and begins reproducing within a week. A single aphid can produce 12 offspring per day. Do the math on that over a growing season and you get populations in the billions.

They feed by inserting needle-like mouthparts into plant tissue and sucking out phloem sap. The sugary waste they excrete is called honeydew. That honeydew is what coats your car, attracts ants, and grows the black sooty mold that makes everything look terrible.

Dozens of species attack trees. The most common troublemakers:

• Crapemyrtle aphid — the most common pest on crape myrtles. Produces heavy honeydew and sooty mold.
• Green peach aphid — attacks fruit trees, maples, and ornamentals. One of the most widespread species.
• Woolly apple aphid — produces white cottony masses on bark and roots. Can cause galls.
• Black cherry aphid — targets cherry and plum trees, causing severe leaf curling.
• Tuliptree aphid — feeds on tulip poplars and produces extraordinary amounts of honeydew.
• Giant bark aphid — the largest North American aphid at 1/4 inch, feeds on oaks, sycamores, and pecans.

The IPM decision framework

The standard approach for aphids is Integrated Pest Management (IPM). This isn’t a spray schedule. It’s a decision tree.

Step 1: Confirm it’s actually aphids

Look for small (1/16 to 1/8 inch), pear-shaped insects with two tube-like projections (cornicles) sticking up from their rear end. Colors range from green to black to pink to white. They cluster on the undersides of leaves and on new growth. If you see sticky honeydew, ants marching up the trunk, or black sooty mold, aphids are the likely cause.

Step 2: Check for natural enemies

Before you spray anything, flip over some infested leaves and look for:

• Ladybug larvae — dark, alligator-shaped larvae that eat more aphids than the adults. A single ladybug can consume over 5,000 aphids in its lifetime.
• Aphid mummies — tan or brown swollen aphid bodies with tiny exit holes. These are aphids that were parasitized by tiny wasps. Each wasp parasitizes up to 300 aphids over three weeks.
• Lacewing eggs — tiny oval eggs on hair-thin stalks. The larvae (called “aphid lions”) are voracious predators.
• Syrphid fly larvae — small maggots near aphid colonies. A single larva eats 100-400 aphids during development.

If you see mummies or active predators, stop. The aphid population will likely crash within 1-2 weeks without any intervention from you. Spraying now kills the good guys and lets the aphids rebound worse than before.

Step 3: Assess the damage

Cosmetic damage (wait it out):

• Honeydew dripping on cars and furniture
• Mild leaf curling on new growth
• Sooty mold on leaves (washes off with rain)
• Light yellowing from moderate feeding

Potentially serious (consider treatment):

• Young or newly planted trees showing stress
• Severe defoliation or stunted growth
• Fruit trees with deformed fruit
• Drought-stressed trees with heavy infestations
• No sign of natural enemies after 2 weeks of monitoring

Scout twice per week during late spring when populations grow fastest.

Treatment options (least toxic first)

1. Blast them with water

This is the first line of defense recommended by every extension service I’ve read. A strong spray from a garden hose physically dislodges aphids from foliage. Once knocked off, most cannot climb back up and will die.

How to do it:

• Use a standard garden hose with a jet or shower nozzle. Not a pressure washer.
• Target the undersides of leaves where aphids concentrate.
• Spray early in the day so foliage dries quickly and doesn’t develop fungal problems.
• Repeat every 2-3 days until populations decline.

Water sprays are one of the most effective non-chemical controls. The limitation: it doesn’t reach aphids hiding inside curled leaves, and it’s impractical for very tall trees.

2. Insecticidal soap

Potassium salts of fatty acids disrupt aphid cell membranes on contact, causing rapid dehydration. It’s a contact-only product with zero residual effect, which means it won’t harm beneficial insects that arrive after the spray dries.

Important: Don’t use household dish soap as an insecticide. Modern dish soaps contain fragrances, antibacterial agents, and additives that burn plant foliage. Use commercial insecticidal soap (like Safer Brand) or pure liquid castile soap at 1 tablespoon per quart of water.

Spray must thoroughly coat all leaf surfaces, especially undersides. Reapply every 5-7 days as needed. Insecticidal soap is the best choice for crapemyrtle aphids because it kills aphids without harming the beneficial insects keeping populations in check.

3. Horticultural oil

Works by suffocating insects and eggs. Two types matter:

• Dormant oil — applied in late winter before bud break. Kills overwintering aphid eggs on fruit trees. Timely application of oil leads to fewer miticide and insecticide applications later in the season.
• Summer oil — refined for use on leafed-out plants at 1-2% concentration. Don’t apply when temperatures exceed 90 degrees F.

Horticultural oil is safe for people, pets, and most non-target organisms. It breaks down quickly in the environment.

4. Neem oil

Neem acts as an anti-feedant, repellent, and growth regulator. It disrupts aphid feeding and reproduction but works primarily on immature stages. Mix 1-2 tablespoons per gallon of water and apply every 7-10 days. Don’t apply above 90 degrees F or on drought-stressed plants.

Neem is moderate in effectiveness. It’s better for prevention and suppression than for knocking down a heavy infestation. Use it as part of a rotation with soap and oil, not as your only tool.

5. Systemic insecticides (last resort only)

Imidacloprid (a neonicotinoid) applied as a soil drench gets absorbed by roots and moves through the tree’s vascular system. It takes 2-4 weeks to reach the canopy but provides long-lasting control and kills aphids inside curled leaves that contact sprays miss.

The pollinator problem: Imidacloprid is toxic to bees and other pollinators. It shows up in pollen and nectar. UC IPM and the Xerces Society warn: never apply to trees in bloom or before bloom. Never use on bee-attractive trees like linden, basswood, or fruit trees during flowering season.

Reserve systemic insecticides for situations where other methods have failed, the tree is young or declining, and the damage is clearly threatening tree health.

Cut off the ant pipeline

If you see ants marching up your tree trunk, they’re protecting aphid colonies in exchange for honeydew. Ants fight off ladybugs, lacewings, and parasitic wasps. They physically move aphids to better feeding locations. They even carry diseased aphids away from the colony to keep it healthy.

Eliminating ant access is often enough to crash the aphid population by itself. Once the bodyguards are gone, natural predators move in.

How to stop ants:

• Sticky barriers — wrap a band of Tanglefoot or similar sticky material around the trunk. Put a layer of fabric or masking tape down first to protect the bark. Check and refresh every few weeks.
• Ant bait stations — place around the base of the tree. Workers carry poisoned bait back to the nest, which eliminates the colony over time. More effective than contact sprays.
• Prune branches touching fences, structures, or the ground. Eliminate alternate pathways ants use to bypass trunk barriers.

Prevention: stop aphids before they start

Watch the nitrogen

High levels of nitrogen fertilizer favor aphid reproduction. Excess nitrogen pushes soft, succulent new growth that aphids find irresistible. Use slow-release or organic fertilizers. Apply nitrogen in small portions throughout the season rather than one heavy dump. Check our spring tree care guide for proper fertilizing schedules.

Plant for the predators

Attract beneficial insects by planting flowers that provide nectar and pollen throughout the growing season. The best plants for attracting predators:

• Yarrow, cosmos, and coreopsis for lacewings and syrphid flies
• Dill, fennel, and cilantro for parasitic wasps
• Buckwheat for generalist predators
• Let some herbs bolt and flower rather than cutting them back

These insectary plantings create a standing army of predators that responds to aphid outbreaks before you even notice them.

Choose resistant varieties

For crape myrtles specifically, hybrid cultivars (Lagerstroemia indica x fauriei) like ‘Natchez,’ ‘Muskogee,’ ‘Tuscarora,’ and ‘Acoma’ show moderate aphid resistance. If you’re planting new crape myrtles, start with resistant varieties and save yourself years of fighting.

Trees most likely to get aphids

Some trees attract aphids more than others. If you’re dealing with recurring infestations, your tree species might be part of the problem.

High susceptibility:

• Crape myrtles — the crapemyrtle aphid is nearly universal on this species
• Fruit trees — apple, cherry, plum, peach all have dedicated aphid species
• Tulip poplars — the tuliptree aphid produces extraordinary honeydew
• Birch (especially river birch) — witch hazel gall aphids cause leaf galls
• Flowering plums — UC IPM specifically flags these as reliable aphid hosts

Moderate susceptibility:

• Maples (especially silver maple) — commonly affected by sooty mold. See our maple tree guide for species comparisons and our maple diseases guide for distinguishing aphid damage from actual diseases.
• Elms (Chinese elm) — woolly aphids and sooty mold
• Hollies — sooty mold from aphid honeydew
• Oaks and sycamores — host the giant bark aphid

If your tree has a history of severe aphid problems year after year, the tree may be stressed from other causes. Aphids exploit weak trees. Address underlying issues like compacted soil, poor drainage, or storm damage first.

When to call an arborist

Most aphid problems resolve on their own or with the basic methods above. But call an ISA Certified Arborist when:

• The tree is too tall to treat from the ground (trunk injection or canopy spraying requires specialized equipment)
• The tree is in obvious decline and you’re not sure whether aphids are the cause or a symptom of deeper problems
• You’ve tried cultural controls for 3-4 weeks with no improvement
• You’re considering systemic insecticides and want professional guidance on timing, application, and pollinator safety

An arborist can also assess whether the tree’s overall health is contributing to recurring pest problems. Sometimes the answer isn’t treating the aphids. It’s improving the soil, adjusting watering, or addressing root issues that are stressing the tree.

Frequently asked questions

Will aphids kill my tree? Rarely. Established, healthy trees tolerate aphid feeding and outgrow the damage. Most aphid damage is cosmetic. Young trees, drought-stressed trees, and trees with recurring severe infestations are at higher risk.

Should I buy and release ladybugs? Purchased ladybugs tend to fly away within days. You’re better off attracting native populations by planting insectary flowers and avoiding broad-spectrum pesticides that kill beneficial insects.

Does dish soap work as an insecticide? Don’t use household dish soap on plants. Modern dish soaps contain fragrances, antibacterial agents, and other additives that can burn foliage. Use commercial insecticidal soap or pure liquid castile soap instead.

Why do ants protect aphids? Ants farm aphids for their honeydew (a sugary waste product). In return, ants protect aphid colonies from predators, remove diseased individuals, and even move aphids to better feeding locations. Controlling ants often controls the aphid problem by exposing colonies to natural predators.

When is the best time to spray for aphids? Only spray when natural enemies are absent and the infestation is severe enough to threaten tree health. If you must spray, early morning is best so foliage dries quickly. For dormant oil on fruit trees, apply in late winter before bud break. For insecticidal soap during the growing season, apply every 5-7 days when temperatures are below 90 degrees F.

How do I prevent aphids next year? Reduce nitrogen fertilization (aphids love lush new growth), plant flowers that attract beneficial predatory insects, control ant access to tree canopies, choose resistant cultivars when planting new trees, and maintain overall tree health through proper watering and mulching.