Aphids
Aphids are small, soft-bodied sap-sucking insects (green, black, brown, or pink) that cluster on the softest, fastest-growing parts of a tree — new shoot…
Aphids at a glance
| Also known as | Greenfly, blackfly, plant lice |
|---|---|
| Affected parts | New shoots, buds, leaf undersides |
| Most at risk | Soft new growth on most species; flowering/fruiting trees and tender tropicals |
| Main cause | Sap-sucking aphids colonising tender new growth |
| Severity | Usually mild–moderate; weakens growth and spreads virus/sooty mold |
| Reversible? | Yes — easily controlled |
What to look for
- Leaves: New leaves curled, puckered, or distorted; clusters of soft insects on the undersides and growing tips; a sticky, shiny coating (honeydew) on leaves below; later, black sooty mold on the honeydew. White cast skins shed by the colony.
- Whole tree: Ants running up the trunk (farming the aphids); buds and shoot tips swarming with the insects; stunted, twisted new growth.
Overview
Aphids are small, soft-bodied sap-sucking insects (green, black, brown, or pink) that cluster on the softest, fastest-growing parts of a tree — new shoot tips, flower buds, and leaf undersides. They reproduce very quickly, distort new growth, and excrete sticky honeydew that draws ants and grows black sooty mold. Common but among the easiest pests to control.
Causes
Soft, lush new growth (often after high-nitrogen feeding); warm spring/summer conditions; migration from nearby plants; and ants protecting colonies from predators.
Commonly confused with
Whitefly and scale also produce honeydew/sooty mold — but aphids are larger, soft, and clustered on tips (whitefly are tiny white flies that scatter when disturbed; scale are fixed bumps). Distorted growth can also be mite or weevil damage; aphids are visible to the naked eye.
Which species are affected
Almost all species, on soft new growth; especially flowering/fruiting trees (crabapple, ume, roses-family), elms, maples, and tender tropicals.
Treatment
Knock them off with a jet of water; squash small colonies by hand; spray insecticidal soap, neem, or horticultural oil, repeating after ~1 week. Control ants, which protect aphids. Encourage/allow ladybirds and lacewings outdoors. Heavy or persistent cases: a systemic insecticide.
Prevention
Don't over-feed nitrogen (which drives soft, aphid-prone growth); inspect new shoots in spring; quarantine new plants; keep predators around outdoors.