Greenfly and Aphids: How to Get Rid of Them

Aphids are easy to control organically as long as you act early and feed the predators. Catch a colony while it is small, knock the numbers back by hand or with water, and let ladybirds and hoverflies do the rest. A spray is almost never the answer.

How to recognise them

Aphids are tiny sap-sucking insects, soft-bodied and pear-shaped, usually clustered on the softest growth — the tips of shoots, flower buds and the undersides of young leaves.

Greenfly are the pale green ones you will see on roses, beans, courgettes and almost everything else. Blackfly are the same kind of pest in black, and they swarm broad beans in particular — see our guide to dealing with blackfly on beans for that crop.

The other tell-tale signs:

• Sticky leaves. Aphids excrete a sugary residue called honeydew that coats the leaves below them.
• Sooty mould. A black, dusty fungus grows on that honeydew, leaving leaves looking grubby.
• Ants running up and down the stems. Ants farm aphids for the honeydew and will even defend them, so a line of busy ants is a good clue.
• Curled, puckered or distorted new growth, and sometimes a slowing of the plant.

A few aphids do no real harm. It is the fast-building colonies on seedlings and soft new shoots that are worth acting on.

Control, ranked

Start at the top and only move down if you need to.

1. Squash them by hand. For a small colony this is the quickest fix of all. Run finger and thumb up the shoot and wipe them off, or pinch out a badly infested growing tip altogether. Do this every couple of days and you will often stay on top of it without anything else.

2. Blast them off with water. For bigger numbers, a sharp jet from the hose or a spray bottle knocks them clean off the plant. Aphids are feeble and most never make it back. Aim under the leaves and repeat every few days. This works brilliantly on sturdy plants like roses and beans; go gentler on soft seedlings.

3. Encourage predators — the real long-term answer. Ladybirds, hoverfly larvae and lacewings eat aphids in enormous numbers; a single ladybird larva can clear hundreds. Bring them in by attracting beneficial insects with flowers and a no-spray garden, and they will police your plants for free, year after year. This is the heart of organic, no-spray growing.

4. Insecticidal soap — last resort only. A soft-soap spray (or a few drops of washing-up liquid in water) coats and kills aphids on contact. Use it only on a stubborn, heavy infestation, spray in the evening, and accept it kills the good bugs too. It is a blunt tool, not a routine.

Why not to spray

Reaching for a pesticide is usually a step backwards. Sprays kill ladybirds, hoverflies and lacewings just as readily as aphids — and the predators are slower to recover, so you end up more dependent on spraying. You also lose the bees and other pollinators caught in the crossfire.

Aphids breed astonishingly fast, so a garden kept spray-free and full of predators settles into a balance that does the job for you. For the full approach, see our guide to natural pest control.

Prevention

A few habits keep aphids from ever building up:

• Grow flowers among the veg. Open, simple flowers like calendula, poached egg plant and the umbellifers (dill, fennel, coriander left to flower) feed hoverflies and ladybirds. Companion planting for this reason genuinely works.
• Go easy on the nitrogen. Over-feeding pushes out a flush of soft, sappy growth that aphids love. Feed sensibly rather than forcing growth.
• Check often, act early. A two-minute look at the shoot tips twice a week means you catch colonies while a squash or a hose still settles it.
• Let a few aphids be. A pristine, aphid-free garden starves its own predators. A little tolerance keeps the balance tipped your way.

Get the predators working and aphids stop being a job at all. They become just another part of a garden that mostly looks after itself — the whole idea behind organic, no-spray growing.

PS — sticky leaves and a few ants are nothing to panic over. Wipe off the worst, plant a few flowers, and let the ladybirds clock in.