Aphids on houseplants: how to identify and treat them

Aphids — the fastest multipliers

Aphids are small, soft-bodied insects that look like tiny pear-shaped droplets. They are often found in large clusters, because they prefer the tender new growth of stems, leaves and flower buds. They feed by sucking sap from the plant, which weakens it and distorts new growth.

What to look out for

Clusters of small insects — Look for groups of green, white, black, or pinkish insects gathered on new stems, flower buds, or the undersides of leaves. Aphids often concentrate near the centre of the plant, where new leaves are unfurling, hiding in tight crevices for protection.
Curled or distorted leaves — As aphids feed on developing leaves, the new growth may come in twisted, puckered, or stunted.
Sticky residue (honeydew) — Like other sap-sucking pests, aphids excrete sticky honeydew. Leaves may look shiny or feel tacky to the touch.
White flakes — As aphids grow they shed their outer skins. You may notice tiny white flakes — ghost-like shells — on the leaves below the infestation.

Examples of aphids in real homes

Aphids clustered on the underside of a leaf — A cluster on the leaf underside

Green aphids gathered on new plant growth — Gathered on the tender new growth

Dense aphid colony along a stem — A dense colony along the stem

Aphids concentrated near unfurling leaves — Concentrated where new leaves unfurl

Aphids hiding in tight crevices of a plant — Hiding in the tight crevices

Curled, distorted leaf from aphid feeding — Curled growth from feeding damage

Shed aphid skins scattered on a leaf — Shed skins — the tell-tale white flakes

Aphids on a flower bud — On the flower buds

Widespread aphid infestation on a houseplant — A widespread infestation

Why they’re difficult to eliminate

Aphids reproduce extremely quickly — many species can reproduce without mating, which means a few aphids can multiply into a large colony within a very short period of time.

How to treat them

Isolate immediately — Move the affected plant to a separate room to stop the infestation spreading to other plants.
Rinse the plant — Take it to the sink or shower and use a steady stream of water. Because aphids are soft-bodied and do not cling tightly to plants, a strong rinse removes large numbers of them. A mild soap solution helps dislodge the rest.
Prune heavily infested areas — Remove heavily infested leaves or stems with clean scissors and dispose of them immediately.
Use an insecticide — Apply an insecticide thoroughly across the entire plant, including the stems and the undersides of leaves — paying close attention to the centre of the plant where new growth is emerging. Repeat weekly for about 5 weeks to break the pest life cycle.
Introduce a biological control — Beneficial insects such as ladybugs or lacewings naturally feed on aphids and can help reduce infestations, especially in larger plant collections.
Eliminate ants — Ants "farm" aphids for the honeydew they produce and will protect them from predators. If ants are present they must be eliminated too — or the aphid infestation will likely return.