How do I get rid of aphids?

Aphids reproduce extremely fast, but so do their predators once they arrive. The usual mistake is spraying something that kills both, which removes the natural control and guarantees a bigger outbreak in a fortnight.

What you'll need

• Hose or spray bottle
• Washing-up liquid (optional)
• Gloves (optional)

Step by step

1. Check the growing tips and leaf undersides.Aphids cluster on soft new growth. That is where to look and where to treat.
2. Squash them by hand where you can.Run finger and thumb up the stem. Unpleasant and highly effective for small outbreaks.
3. Blast them off with a jet of water.Aphids that fall off mostly do not climb back. Repeat every few days and this alone handles most infestations.
4. Make a soap spray if the problem persists.A teaspoon of plain washing-up liquid in a litre of water. Spray the undersides thoroughly — it works by contact, so coverage is everything.
5. Test the soap spray on a few leaves first.Some plants are sensitive. Wait a day and check for scorching before treating the whole plant.
6. Encourage predators rather than eliminating pests.Ladybirds, hoverflies, lacewings and small birds eat aphids in large numbers. Flowers such as marigolds and fennel bring hoverflies in.
7. Deal with ants if they are farming the aphids.Ants protect aphids for their honeydew and drive predators off. A grease band or barrier on the stem breaks that relationship.
8. Cut back badly infested soft growth.On roses and beans, removing the affected tips takes most of the colony with it and the plant regrows quickly.

Tips

• Sooty black mould on leaves grows on aphid honeydew. Treating the aphids stops the mould; washing leaves deals with the appearance.
• Overfed plants produce soft sappy growth that aphids prefer. Excess nitrogen genuinely makes the problem worse.
• Broad-bean blackfly is largely prevented by pinching out the growing tips once the plants are flowering.

Common mistakes

• Using a broad-spectrum insecticide — It kills ladybirds, hoverfly larvae and lacewings along with the aphids, and the aphids recover much faster than the predators.
• Spraying only the tops of leaves — Aphids sit underneath. A contact spray that does not reach them does nothing.
• Treating once and stopping — Aphids reproduce continuously. Repeat every few days for a fortnight to break the cycle.

Questions people ask