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Aphids: how to recognise and treat it

Pest

Aphids — Photo: Alvesgaspar, CC BY-SA 4.0, Wikimedia Commons

Symptoms

Colonies of small soft-bodied insects — green, black, yellow, pink or grey — on shoot tips, flower buds and the undersides of young leaves.
Curled, distorted young leaves and stunted shoots; white cast skins on the leaves.
Sticky honeydew on leaves, often with black sooty mould and ants climbing the plant.

Organic treatment

Squash small colonies with finger and thumb, or knock them off with a strong spray of water early in the day; repeat as needed.
Spray insecticidal soap (potassium salts of fatty acids) or a plant oil such as neem, wetting leaf undersides; it kills only the aphids it hits, so repeat. Do not spray drought-stressed plants or in hot weather.
Cut off heavily infested shoots and curled leaves where sprays cannot reach.

Chemical treatment

Insecticide with pyrethrins (often mixed with insecticidal soap) — it breaks down quickly; spray in the evening away from open flowers to protect bees and follow the label dose and pre-harvest interval.

Reference information, not a guarantee. Read and follow the label of any product: dose, safety and the days to wait before harvest.

Prevention

Check shoot tips and leaf undersides often; in spring give ladybirds, hoverflies and lacewings time to catch up before acting.
Do not overfeed with nitrogen — use slow-release fertiliser in small doses; soft lush growth favours aphids.
Grow flowering plants nearby that give nectar and pollen to the aphids' natural enemies.

Sources

Figures checked against these sources.