Aphid Control: How to Get Rid of Aphids on Plants Without Making Things Worse

You turn over a leaf on your tomatoes, roses or a houseplant and find it crowded with tiny soft insects, maybe with sticky leaves and ants running up the stem. Those are aphids. They are one of the most common plant pests in the country, and also one of the easiest to overreact to. This guide helps you confirm what you have, decide whether it needs action, and pick the gentlest fix that works.

How to identify aphids

Aphids are small (about 1/16 to 1/8 inch long), soft-bodied and shaped like a pear. Look closely at the rear end: most species have two short tubes sticking out backward. These are called cornicles, and they are the best single clue that you are looking at an aphid.

Other features:

• Color varies by species and plant. Green, yellow, black, brown, red and gray are all common. Some species are coated with white wax and look woolly.
• Wingless and winged forms. Most aphids in a colony have no wings. Winged adults show up when a colony gets crowded or when the seasons change in spring and fall, and they fly off to start new colonies.
• Slow movers. Aphids cluster on new shoots, buds and leaf undersides and do not scurry when disturbed.
• Shed skins. Pale, empty skins stuck to leaves are a common sign of a growing colony.

If you see fine webbing and speckled leaves instead of visible clusters, read the spider mite guide.

Signs and damage

A few aphids on a healthy plant are nothing to worry about. Many infestations cause little or no lasting harm. Watch for these signs that a colony is getting large:

• Curled, puckered or yellowing leaves, and stunted new shoots. Some species inject saliva that twists leaves or forms galls.
• Honeydew. Aphids excrete a sticky, sugary liquid that coats leaves, cars and patio furniture under infested trees.
• Sooty mold. A black fungus grows on honeydew. It does not infect the plant, but it blocks light and looks bad.
• Ants on the plant. Ants feed on honeydew and guard aphids from predators. A line of ants climbing a tree trunk often means aphids above.
• Virus symptoms. Some aphids spread plant viruses, such as cucumber mosaic. Mottled, yellowed, curled and stunted plants can result, and the infection can happen before you could have controlled the aphids.

Why aphids show up

Aphids reproduce fast and favor soft, fast-growing plant tissue. Three conditions make outbreaks worse:

• Heavy nitrogen fertilizer. Lush new growth from a big dose of fertilizer feeds aphid reproduction.
• Ants protecting the colony. Ants chase off lady beetles and parasitic wasps.
• Loss of natural enemies, usually after a broad-spectrum insecticide spray.

How to get rid of aphids, step by step

Work through these steps in order. Most home gardens never need to go past step 5. This order follows the integrated pest management approach.

1. Check plants often. During spring and early summer growth, look at shoot tips and leaf undersides at least twice a week. Note whether you see lady beetles, lacewing larvae or “mummies” (see below).
2. Spray them off with water. A strong stream from the hose knocks aphids off sturdy plants, and most cannot climb back. Do it in the morning so leaves dry fast. Repeat every few days as needed. This also rinses off honeydew and sooty mold.
3. Prune the worst spots. Clip and bag heavily infested shoots and curled leaves. Curled leaves shelter aphids from sprays and predators, so removing them does a lot of good.
4. Protect natural enemies. Lady beetles (adults and larvae), green lacewing larvae, syrphid fly larvae and soldier beetles eat aphids. Tiny parasitic wasps lay eggs inside aphids, which turn into swollen, tan or brown, crusty mummies. If you see mummies, the population is likely to crash within a week or two on its own. Buying and releasing lady beetles gives short-lived help at best, since most fly away.
5. Manage ants. If ants are tending the colony, block them. Wrap a band of sticky material around tree and shrub trunks (put a layer of tape or fabric under it on thin bark), prune branches that touch buildings or other plants, and use ant baits rather than sprays. Our ant control guide covers baits in more detail.
6. Go easy on nitrogen. Use slow-release fertilizer in smaller, spaced-out doses instead of one large feeding.
7. Use insecticidal soap or horticultural oil if you still need to. See the next section.

Insecticidal soap and horticultural oil

These are the lowest-risk sprays for aphids. They kill by contact and leave little residue, so they spare most of the predators that arrive after you spray.

• Coverage matters most. They only kill aphids they touch. Wet the undersides of leaves and the shoot tips.
• Expect to repeat. Neither product keeps working after it dries, so new aphids hatching or flying in are not affected.
• Watch for plant injury. Do not spray plants that are water stressed or when temperatures are above about 90°F. Some plants are sensitive, so test a few leaves and wait a day or two before spraying the whole plant.
• Read and follow the label for which plants it is safe on and how to mix it. Use a product sold for plants, not dish detergent.

Skip broad-spectrum insecticides. Products in the organophosphate, carbamate and pyrethroid classes kill lady beetles, lacewings and parasitic wasps along with the aphids. With the predators gone, surviving aphids rebound fast, and repeated use can also breed resistance. The usual result is a bigger aphid problem a few weeks later.

Insecticides that move through the plant

Some insecticides are taken up by roots or leaves and carried inside the plant, so aphids feeding on the sap are killed. Products containing imidacloprid are one example. They can work on serious infestations of trees and shrubs, but they also harm predators, parasitic wasps and pollinators.

• Never apply them to plants in bloom or about to bloom, since bees can be exposed through the flowers.
• Do not use them on vegetables or fruit unless the label allows that crop.
• Check local rules. UC IPM reports that, as of January 2025, these products are available only to licensed pest control professionals in California. Rules differ by state.

Read using pesticides safely before you buy any insecticide, and read and follow the label.

Aphids on houseplants

Indoors, there are no natural enemies to help, so act early. A spray of water knocks aphids off, and you can wipe them from sturdy leaves with a cotton swab dipped in rubbing alcohol. Prune badly infested stems, and throw out a cheap plant that is heavily infested. Insecticidal soap is one of the few sprays labeled for indoor plants, but some plants are sensitive, so read the label. To prevent repeat problems, keep new plants apart from your others for about 30 days and check them often.

When to call a professional

Most aphid problems are a garden chore, not a service call. Consider an arborist or licensed applicator if:

• A large tree is dripping honeydew on cars, decks or walkways every year and you cannot reach the canopy with water or soap.
• A prized tree or shrub keeps losing new growth season after season.
• You think a treatment that moves through the plant is warranted. A professional can judge timing around bloom and local rules.

Aphid questions

Will aphids kill my plant? Rarely. Most infestations cause little or no lasting harm, and extension specialists say treating aphids purely for plant health is usually unnecessary. The bigger risk is an aphid-spread virus in vegetables and flowers.

Why do I keep seeing ants on my plant? They are farming the aphids for honeydew and protecting them from predators. Control the ants and natural enemies can do their job.

Do I need to buy lady beetles? Usually not. Store-bought lady beetles released in daylight tend to fly off right away and leave your yard within days. The ones that show up on their own, along with lacewings and parasitic wasps, do more good. Protect them by skipping broad-spectrum sprays.