How to get rid of aphids on houseplants without harsh sprays

Aphids are small, soft, sap-sucking insects. Indoors they're active all year (RHS), and they multiply quickly, so the key is to start the moment you spot them and to keep repeating. Washington State University's PestSense puts non-chemical methods first, and the RHS advises avoiding pesticides wherever possible.

How to get rid of aphids

1. Check that they really are aphids.

   

   Look at shoot tips, flower buds and the undersides of young leaves (RHS). Aphids are about 1 to 7 mm long (RHS) and are most often green or black, though some are yellow, pink, white or mottled; a few are covered in white, woolly wax (RHS, University of Maryland Extension).

   Other clues: sticky leaves or surfaces under the plant (honeydew), black sooty mould on that stickiness, curled or distorted leaves, and white cast skins on the leaves (RHS, University of Maryland Extension).

   You should see: soft-bodied insects that squash easily, usually in groups, mostly without wings (WSU).

2. Move the plant away from your other plants.

   

   Aphids spread from plant to plant by crawling or flying (WSU). Put the plant in another room until it's clear, and check its neighbours leaf by leaf. WSU suggests keeping any new or moved plant apart, in a spare room for example, for about a month.

   You should see: the affected plant on its own, with no leaves touching other plants.

3. Snip off the worst shoots, and squash small groups.

   

   WSU suggests pruning out heavily infested leaves and shoots. Bag them and put them in the bin. The RHS says small colonies can simply be squashed between finger and thumb.

   You should see: no tight, curled leaves left on the plant. Aphids hide inside them, where sprays and water can't reach (Colorado State).

4. Rinse the plant in lukewarm water, especially under the leaves.

   

   WSU says to wash plants in the shower or sink with lukewarm water, which removes aphids, honeydew and sooty mould. Use a gentle spray and turn the leaves so the water hits the undersides, where aphids gather. The University of Maryland Extension agrees aphids can be washed off with water.

   Let the pot drain fully before you put it back.

   You should see: clean leaves with no insects and no sticky shine on them.

5. Careful: too much alcohol can harm some plants. Test it on a single leaf first (WSU).

   Wipe off stragglers with a cotton bud dipped in rubbing alcohol.

   

   Rinsing rarely gets every aphid. WSU suggests removing the rest with cotton buds or cotton wool moistened with rubbing alcohol. Check leaf joints and the tips of new shoots. Wipe any remaining sticky residue or sooty mould off the leaves with a damp cloth (RHS).

   You should see: no aphids left anywhere on the plant, and the tested leaf unharmed.

6. Careful: some plants are injured by soap sprays. Test the spray on a small area a day or two before you treat the whole plant (Colorado State). Read the label and check it covers your plant and aphids (University of Maryland Extension). Don't use it on herbs or other plants you eat (WSU).

   If they keep coming back, spray with insecticidal soap.

   

   Use an insecticidal soap labelled for indoor plants (University of Maryland Extension). Soap only kills the aphids it actually wets and leaves nothing behind afterwards (Colorado State), so cover the undersides of the leaves and the shoot tips thoroughly.

   Because it has no lasting effect, repeat sprays every four to seven days may be needed, but keep the number of sprays down to avoid damaging the plant (Colorado State). Follow the label for how often. Don't use washing-up liquid instead: Colorado State says dish soaps can injure plants.

   You should see: dead, shrivelled aphids the next day, and no spotting or scorching on the leaves.

7. Check again every few days, and repeat.

   

   Aphids that drop off during washing climb back up, so WSU says to rinse regularly. Check the undersides of the leaves and new shoots each time. Frequent checks let you act before damage builds up (RHS).

   You should see: fewer aphids each time you look, then none.

Aphids or something else?

The RHS says woolly aphids can be mistaken for scale insects, mealybugs or whitefly. Before you treat, check which you have.

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