How To Get Rid of Aphids on Plants: Organic Sprays, Ladybugs, and Companion Planting
Quick Reference
- Fastest fix: a firm blast of water from a garden hose knocks most aphids off a leaf and few return.
- Biological control (best long term): ladybird beetles, lacewings, aphid midges, hover flies, and parasitic wasps eat aphids at every stage. Attract them with dill, fennel, and yarrow.
- Organic sprays that work: insecticidal soap, horticultural oil, and pyrethrin. Follow the label; cats and fish are especially sensitive to pyrethrin.
- 4,000+ species worldwide: roughly 250 are crop or ornamental pests. The green peach aphid alone attacks over 500 host plants (University of California Integrated Pest Management).
- Reproduction speed: a single wingless stem mother can birth up to 100 nymphs in a month, all female, all able to reproduce within a week in summer heat.
- What NOT to do: do not apply nitrogen fertilizer during an infestation; nitrogen pushes soft new growth that aphids prefer.
Finding aphids on plants can be alarming, especially when an infestation seems to happen overnight. Do not panic. Aphids generally will not kill mature plants and often affect only a portion of new growth. They can, however, transmit plant viruses that do the killing, which is why we recommend immediate treatment and removal. The suggestions below will help you win the fight against these pests without reaching for harsh chemistry first.
Aphid guidance across this article draws on University of California Integrated Pest Management and the University of Minnesota Extension, both of which favor prevention and biological control over broad-spectrum sprays.
What Are Aphids?
Aphids are small insects, about 1/16 to 1/8 inch in size, with soft bodies. Most are green in color, but hues vary depending on the variety. More than 4,000 species have been identified around the world, with about 250 known as crop and ornamental pests. The most common is the green peach aphid, which is found worldwide on more than 500 host plants, including potato, cherry, and rose.
Aphids are sap suckers, equipped with mouthparts that pierce the tender parts of a plant (stems, leaves, and roots) and draw out fluids. They have antennae, long legs, and cornicles (tubelike appendages located at the hind end that secrete a substance to ward off predators). They are mostly wingless, though some varieties do develop wings.
How To Control and Avoid Aphids
It may be as easy as wiping the bugs off the plant with your hand or a damp cloth. Or it may take more work if, say, an entire row of peas is covered. Knowing the aphid life cycle helps you decide which control fits.
Life Cycle
Aphids have a complex reproductive method, part of which accounts for the sheer number of insects that can infest a plant in a short period of time. In a single growing season, multiple generations may be born, all of which continue to reproduce.
If you think aphids come from eggs laid by a female, you are partly correct. Most species overwinter as eggs (and in some climates as adults) on host plants or in plant debris. But to reach the overwintering egg stage, we need to look at how these insects live and grow during the growing season.
When the eggs hatch, what emerges are wingless females called stem mothers. These aphids do not lay more eggs; instead they give birth to live aphids, called nymphs, which look like tinier versions of an adult. Over the course of about a month, a single stem mother can have up to 100 nymphs. All of the nymphs are female and can mature in a week in summer temperatures and start giving birth to more nymphs.
When the ever-expanding colony on a host plant begins to grow too crowded, females with wings emerge. Those winged females fly off to a new location and begin to colonize that host.
Lower temperatures and shortened days signal aphids to shift strategies. That is when they give birth to not just females but also males, which develop wings and migrate to locations favorable for overwintering. The aphids mate and the females lay the eggs that will overwinter and emerge in spring as the next generation of stem mothers.
Prevention Techniques
Prevention is the first line of defense. First, consider which plants are most attractive to aphids. The three top families are aster, conifer, and rose. The aster family includes more than 23,000 species, with plants such as aster, coneflower, daisy, sunflower, and zinnia. Conifers have about 630 species, from cedar to fir to larch to pine to redwoods, yews, and spruces. The rose family covers 3,000 species that include roses, strawberries, apples, almonds, blackberries, and more. Here are a few habits that shrink the aphid opportunity:
- Remove plant debris in the fall to eliminate overwintering locations.
- Eliminate weeds, especially around seedlings, to stop the transfer of aphids from one location to another.
- Knock the aphids off, by hand or using water sprayed from a regular garden hose. Most will not return to the plant.
- Do not use a nitrogen fertilizer during an aphid infestation; nitrogen pushes soft new growth aphids prefer, and the infestation gets worse.
- Use a lightweight fabric row cover to protect young plants.
- Use reflective silver mulch or mylar. Light reflected on the underside of leaves acts as a repellent. An added benefit is that the increase in light often means an increase in yield. In place of reflective mulch, disposable aluminum pie plates with a hole in the center offer similar aid, as does aluminum foil, matte side against the soil.
Signs to Watch For
Signs of an aphid infestation may show up in a number of ways long before you notice the tiny aphids themselves, which tend to hide on the underside of leaves and in less noticeable locations.
- Sticky, shiny coating on leaves and stems: aphids excrete a sugary water known as honeydew, which coats leaves and stems of an infected plant. In great quantities, it drips off the plant. A side effect: honeydew attracts sugar-loving ants (ants have been known to protect aphids, even carrying them from plant to plant and overwintering their aphids in their own nests).
- Black sooty mold: the honeydew above also promotes growth of a fungus called sooty mold. It appears as black soot on affected leaves and can interfere with photosynthesis.
- White casts: aphids molt and leave behind white casts on leaves and stems.
- Leaf curl, leaf wilting, stunted shoot growth. On certain plants, abnormal plant growths called galls may also be present.
Plant Controls
Companion planting has long been used to ward off garden pests, including aphids. Here are some helpful pairings:
- Marigolds: strong-scented flowers such as marigolds mask the smell of attractive host plants.
- Nasturtiums and okra: these are known as trap plants because they draw aphids toward them and away from the crop you want to protect.
- Alliums: chives and garlic are excellent repellents. Peas and beans dislike garlic and should not be planted nearby.
- Dill, fennel, basil, rosemary, and lavender also tend to repel aphids and, in the case of dill and fennel, attract beneficial insects that eat them.
- Peppermint also works, but given that it is a mint and a perennial, be aware it can spread like wildfire and become a weedy pest.
Other Biological Controls
Sometimes nature itself provides relief from an aphid invasion. These are biological controls, some of which are commercially available. A number of insects prey on aphids, including ladybird beetles (ladybugs), lacewings, aphid midges, hover flies, and parasitic wasps. Some fungi can also infect and kill aphids, and several bird species eat them.
Parasitic wasps, for example, lay their eggs inside the aphid; the wasp larvae then eat the aphid from the inside while the outside hardens, creating what is called a mummy. Inside the mummy, the larva develops, emerging as the adult wasp.
Other insects feed on aphids, such as ladybird beetles and lacewings. Perhaps best known as aphid predators are ladybirds, which are readily available for purchase. Releasing these into a greenhouse setting (rather than outdoors, where they usually fly away) is a recommended use.
Observation is the best way to see if nature is helping control the aphid infestation. The presence of mummy shells where the aphids are shows the wasps are active. The presence of ladybirds and lacewings on plants shows available predators.
Chemical Controls
Chemical controls are another method of management, but be aware there are potential problems with any chemical application, particularly harm to beneficial garden insects, including aphid predators. Chemicals also can damage or kill plants, especially in warm weather when temperatures are high or when plants are in drought. In many situations, the solution is more harmful to the plant than the damage the aphids do.
Some chemical applications that may be useful include (follow all instructions for usage and application, including time of day, susceptible plants, food-crop safety, and vulnerable insects):
- Insecticidal soap
- Horticultural oil
- Pyrethrin
Note: Cats and fish are particularly sensitive to pyrethrin.
Disease Transmission
Aphids transmit diseases when they cut into and feed off a plant. Aphids spread many mosaic viruses, including cucumber mosaic and potato mosaic. The USDA Animal and Plant Health Inspection Service catalogs aphid-vectored pathogens as a top-tier concern for both backyard growers and commercial producers.
The problem is that a plant can be infected even when the number of aphids is minute, usually long before there are visible signs of an infestation or the aphids are spotted by a visual inspection.
That particular fact makes prevention the best way to control aphids and the damage they can cause.
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Frequently Asked Questions
What is the fastest way to get rid of aphids on plants?
A strong blast of water from a garden hose knocks most aphids off a leaf and few return. For heavier infestations, follow up with insecticidal soap or horticultural oil, both of which target soft-bodied insects like aphids with limited harm to beneficial predators.
What kills aphids naturally?
Ladybird beetles (ladybugs), lacewings, aphid midges, hover flies, and parasitic wasps all prey on aphids. Attract them by planting dill, fennel, yarrow, and cosmos nearby. A soap-and-water spray (a teaspoon of dish soap per quart of water) also works against small colonies.
Do aphids kill plants?
Aphids rarely kill mature plants directly. The larger risk is the plant viruses they transmit, including cucumber mosaic and potato mosaic, which can. Small infestations on established plants may not need treatment, but early control matters most on seedlings and vegetables you plan to eat.
Where do aphids come from?
Most aphid species overwinter as eggs on host plants or in plant debris. In spring, wingless female stem mothers hatch and start giving birth to live nymphs (all female, no males needed) that mature and reproduce within a week in summer heat. When a colony crowds a host plant, winged females fly to new plants.
Are ladybugs good for aphids?
Yes. A single ladybird beetle can eat 5,000 aphids in its lifetime. Purchased ladybugs work best when released in a greenhouse or covered garden; outdoor releases often fly away. Attracting resident ladybugs with dill, fennel, and yarrow is more effective long term.
Does soapy water kill aphids?
Yes. A mild spray of dish soap and water (about a teaspoon per quart) breaks down the aphid’s soft outer body and dehydrates it. Commercial insecticidal soap works the same way with a formulation designed not to burn plant leaves. Spray in the cool of the morning or evening to avoid leaf burn.
What plants repel aphids?
Marigolds, alliums (garlic, chives), dill, fennel, basil, rosemary, lavender, and peppermint all repel aphids. Nasturtiums and okra work as trap crops, drawing aphids away from vegetables you want to protect.
Janine Pineo
Janine Pineo has been gardening all her life in Maine and writing about it for more than two decades. More of her writing can be found on her website, GardenMaine.com.
- Janine Pineo
- Janine Pineo
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I ran into a situation this year with my spirea. They developed aphids for the first time and as I was pruning them I noticed orange bugs with no spots. I’m wondering if those orange bugs without spots were lady bugs? I felt terrible that I removed branches with them on it. I placed the branches in an open compost pile as I didn’t know what to do with them. I hope they managed to fly to other plants to feed on.
The directions on the spirea says to prune after blooming to encourage a 2nd rebloom, which I do for the pollinators. But am I risking lady bugs while doing this?
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