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How to identify it
- Aphids are 1/16 to 1/8 inch (2 to 4 mm) long, with soft, pear-shaped bodies and long legs and antennae. Depending on species and host plant they may be green, yellow, brown, red, gray or black.[4][1]
- Look for a pair of tubelike cornicles, like tiny tailpipes, pointing backward from the rear of the body. UC IPM says they set aphids apart from all other insects.[1][4][7]
- Most adults are wingless, but winged forms appear when colonies get crowded, when the host plant declines, or in spring and fall.[1][6]
- They often feed in dense groups and, unlike leafhoppers, most don't move quickly when disturbed.[1]
- Growing aphids shed their skins, and the white cast skins are often left on leaves or stuck in honeydew.[4]
- The green peach aphid, a pest worldwide, has red eyes and three dark lines down its back.[2][7]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Woolly aphids | A few aphid species look waxy or woolly because they cover themselves with white or gray wax threads; aphids that curl leaves or live on roots are often wax-covered.[1][6] |
| Spider mites | Eight-legged arachnids, not insects, that leave fine silk webbing on infested leaves; aphids don't make webbing.[3][5] |
Where it lives
Aphids occur on plants almost everywhere; the green peach aphid is a pest worldwide, in greenhouses, landscapes, gardens and field crops.[1][2]
Biology and life cycle
For most of the year, females give birth to live young without mating, several a day.[1][6][4]
Young aphids are called nymphs. They molt about four times on the way to adulthood; there is no pupal stage.[1]
Crowding or a declining host plant triggers winged forms that move to new plants. They are poor fliers, but the wind can carry them for miles.[4][6]
In fall many species produce males and egg-laying females, and the eggs survive the winter on the plant, typically in crevices around buds or on stems. Some species alternate between a woody winter host and a different summer host.[4][6]
In the northern United States green peach aphids overwinter as eggs on Prunus trees, while in the Southeast no eggs are laid and up to 30 generations occur a year; a complete life cycle may take as little as 12 days.[2]
Many species do the most damage in late spring, when temperatures are warm but not hot, roughly 65 to 80 degrees F. Summer heat knocks many species back, heavy rain dislodges them, and fungal diseases can wipe out colonies in humid weather.[1][7][4]
Damage and signs
- Low to moderate numbers seldom harm plants. Large colonies can yellow leaves and stunt shoots; some species inject a toxin that curls and distorts leaves, and a few form galls.[1][4]
- They excrete sticky honeydew that often turns black with sooty mold and attracts ants and yellowjackets. Honeydew can drip onto car windshields and lawn furniture under infested trees.[1][4][6]
- Aphids spread plant viruses, including cucumber mosaic virus, on crops such as squash, cucumber, melon, beans, potato and lettuce. Spraying aphids does little to prevent this, because infection happens even when aphids are few and it takes only a few minutes for an aphid to pass on a virus.[1][4]
- Common landscape targets include flowering plums, roses, tulip trees, crape myrtles, apples and many vegetables. In Minnesota the most common landscape aphids are on roses, spirea, poplars, willows, oaks, maples, white pine, lindens and fruit trees.[1][4]
Health risk
Aphids feed only on plants; their harm is feeding damage, honeydew, sooty mold and virus spread. Minnesota says the sooty mold is not harmful to trees and honeydew does not harm plants.[1][4][2]
Control
Prevention
Avoid heavy nitrogen fertilizer, which favors aphid reproduction; use slow-release forms in small amounts through the season.[1]
Protect seedlings with covers, and use silver reflective mulches to repel aphids and cut virus spread in squash and melons.[1]
Sanitation
Pull weeds such as sowthistle and mustard that build up aphids near the garden. On perennials that die back, such as columbine, lupines and perennial asters, remove the old top growth that carries aphid eggs before new shoots come up in spring.[1][4][6]
Traps and physical control
Knock aphids off sturdy plants with a strong spray of water; most dislodged aphids can't climb back. Prune out curled leaves or shoots where colonies are concentrated.[1][4][6]
Biological control
Lady beetles, lacewing and syrphid fly larvae, soldier beetles, parasitic wasps and fungal diseases all kill aphids; crusty golden-brown or black mummies mean wasps are at work. Flowering plants that bloom at different times help keep natural enemies around.[1][6][4][2]
Keep ants off infested plants with sticky trunk bands on a wrap or with ant baits, because ants defend aphids from their natural enemies.[1]
Pesticides
If treatment is needed, insecticidal soaps and oils, including neem and horticultural oils, are the best choices. They kill only the aphids they touch, so cover leaf undersides thoroughly and repeat as needed.[1][2][6][4]
On fruit trees and many shrubs, horticultural oil applied in the dormant season, before bud break, kills overwintering aphid eggs.[1][6]
Longer-lasting sprays such as malathion, permethrin and acephate kill natural enemies and are linked to bee kills; Minnesota warns they can make aphid problems worse. The green peach aphid resists many insecticides, including pyrethroids, and a 2014 review counts at least seven separate resistance mechanisms in it.[1][4][6][2][8]
Systemic insecticides such as imidacloprid can reach aphids hidden in curled leaves, but they are very toxic to pollinators: don't apply them to plants in bloom or about to bloom.[1][4][6]
When to leave aphids alone
Most larger plants tolerate light to moderate aphid numbers with little harm, and populations often crash on their own once natural enemies build up or hot weather arrives.[1][4]
Check plants at least twice a week during rapid growth, looking under leaves and along the upwind edge of the garden.[1]
Because aphids multiply so fast, natural enemies take some time to catch up and bring numbers down.[4][1]
Where sources disagree
How fast colonies grow: UC IPM says females often bear as many as 12 young a day and a newborn can be reproducing in seven to eight days in warm weather; Colorado State says three to five young a day and about 10 to 14 days to full size.[1][6]
Cornicles: UC IPM says most species have them; Minnesota says all aphids do, though on some they are small and hard to see.[1][4]
Green peach aphid color: NC State calls it light to dark green or pink; Wisconsin and Minnesota call it yellowish green.[2][7][4]
Who can buy systemic products: UC IPM says that, as of January 2025, they are available only to licensed pest control professionals; Colorado State says imidacloprid is sold through licensed pesticide dealers, which include many garden centers. Rules differ by state.[1][6]
Common questions
- Why are ants crawling all over my plants?
- Ants collect the sweet honeydew aphids produce and protect the aphids from predators, so a stream of ants up a trunk often means aphids are feeding above.[1][4]
- Do ladybugs bought at the store control aphids?
- Released convergent lady beetles give only temporary control, because most fly away within a few days.[1]
- Will soap sprays kill aphids inside curled leaves?
- No. Contact sprays only kill aphids they touch, so prune out curled leaves where aphids are hidden.[1][6]
- Will aphids kill my plant?
- Rarely. In most cases they cause little or no damage; severe feeding can twist and yellow leaves and stunt or kill shoots.[4][1]
- How do I get aphid honeydew off my car or patio furniture?
- Scrub with dish detergent or a tar remover. Heavy-duty detergents and tar removers can damage paint and clear coat, so test a small spot first.[4]
Sources
- University of California Statewide IPM Program, “Aphids (Pest Notes, Home and Landscape).” ipm.ucanr.edu/home-and-landscape/aphids/ (accessed 2026-11-11)
- NC State Extension, “Green Peach Aphid (PDIC Factsheet, reviewed May 6, 2023).” content.ces.ncsu.edu/green-peach-aphid (accessed 2026-11-11)
- University of California Statewide IPM Program, “Spider Mites (Pest Notes, Home and Landscape).” ipm.ucanr.edu/home-and-landscape/spider-mites/ (accessed 2026-11-11)
- University of Minnesota Extension, “Aphids in home yards and gardens.” extension.umn.edu/yard-and-garden-insects/aphids (accessed 2026-11-11)
- University of Minnesota Extension, “Twospotted spider mites in home gardens.” extension.umn.edu/yard-and-garden-insects/spider-mites (accessed 2026-11-11)
- Colorado State University Extension, “Aphids on Shade Trees and Ornamentals (Fact Sheet 5.511).” extension.colostate.edu/topic-areas/insects/aphids-on-shade-trees-and-ornamentals-5-511/ (accessed 2026-11-11)
- University of Wisconsin-Madison Extension (Wisconsin Horticulture), “Aphids.” hort.extension.wisc.edu/articles/aphids/ (accessed 2026-11-11)
- Insect Biochemistry and Molecular Biology, via PubMed, “The evolution of insecticide resistance in the peach potato aphid, Myzus persicae (Bass et al. 2014).” pubmed.ncbi.nlm.nih.gov/24855024/ (accessed 2026-11-11)
- iNaturalist, “Myzus persicae taxon page (order and family).” www.inaturalist.org/taxa/243745 (accessed 2026-11-11)