How to get rid of whiteflies on houseplants
Tiny white insects that lift off the plant in a cloud. How to tell whiteflies from aphids, what actually kills them, and why they come back.
That cloud of tiny white insects lifting off the plant when you move it is whiteflies, sap-sucking insects that live under the leaves. Move the plant away from the others first. Most advice you have read was written for a vegetable garden, and in a heated room with nothing to eat them, the colony does not die back on its own.
Whiteflies, aphids and the other tiny white bugs
The test is the cloud. Move the plant and whiteflies lift off the undersides of the leaves in a white swarm, and the RHS names that as what separates them from aphids. The adults are 1.5 mm long by the RHS's measure, with four powdery white wings. Under the same leaves sit flat, oval, cream-coloured nymphs that neither move nor look like insects. That is the stage most people miss.
White flecks on the top of a leaf are more likely aphid skins, which aphids shed as they grow. Mealybugs are a third insect, wrapped in cottony wax in the leaf joints, and they do not lift off in a cloud. Indoors two species do nearly all of it, Trialeurodes vaporariorum and Bemisia tabaci, and knowing which one you have changes nothing about what you do next.
How to get rid of whiteflies in five steps
The order decides the outcome, and the step people drop is the last one. Each step does less if you skip the one before it, and what tells you it is over is a clean leaf underside at the next check.
Does neem oil kill whiteflies, and what else works on contact
Neem oil kills the insects it lands on and nothing else. UC IPM puts it with insecticidal soap and petroleum oils as products that control only what is sprayed directly, so this is a question of coverage. Whatever the spray missed, it did not treat.
Insecticidal soap is the home remedy for whiteflies on plants that holds up, and it also works only by contact. The colony sits under the leaves, mostly the lowest ones, which UC IPM calls the hardest to reach. Turn the plant over or rinse it in the shower first. Spray it watered and out of direct sun, because soaps and oils can burn a stressed or hot leaf.
The recipes that pile garlic, cinnamon or shampoo on top of a soap solution work, where they work, because of the soap. As for plants that repel whiteflies, the repellent UC IPM describes is a reflective mulch in a vegetable bed, and none of the six sources describes one plant keeping them off another indoors.
Best insecticide for whiteflies: contact, systemic or biological
The answer to what is the best insecticide for whiteflies is on the back of the bottle. It is the product whose label says it reaches the stage you are dealing with, names your plant and allows indoor use, which the Missouri Botanical Garden sets as the condition. Approval differs by country, so the label is the authority and this page is not. This site sells no insecticide.
- Contact. Insecticidal soap, oils and pyrethrins kill what they wet, mostly adults and young nymphs. Eggs and the last nymph stage resist them better, so they need repeating.
- Systemic. A systemic insecticide for whiteflies goes into the compost and reaches the nymphs through the sap. UC IPM warns about its effect on bees and beneficial insects, especially on plants in flower.
- Biological. Parasitic wasps such as Encarsia formosa, released into a greenhouse. For a few pots at home, UC IPM calls biological control impractical.
- The label. It has to name the pest, your plant and indoor use. If a product stops working, switch to a different active substance, because this insect builds resistance.
Whiteflies on plants indoors, and what that changes
Indoors nothing eats them and nothing stops them breeding. Outdoors, predators and parasitoids keep numbers down as the season goes on, according to the University of Maryland. Whiteflies on houseplants have neither, and because a home stays warm all year, they keep reproducing through the winter. The RHS notes that the greenhouse species thrives only in warmth, which is why it is rarely a problem outside.
Nothing rinses the plant, so you have to. Plants also stand closer together indoors than they ever would in a garden, and a colony crosses a shelf through leaves that touch. If you keep several low light houseplants grouped in one corner, check them all at the same time.
A plant hanging on a wall gets treated like any pot, if you can take it down. A wall canvas like the Living Canvas hangs from two eyelets on two screws, so it lifts off and lies flat on a worktop for spraying. Those screws go into two drilled holes, with masonry plugs in brick and cavity plugs in plasterboard, at a height you can reach without a chair.
What whiteflies damage on a plant, and what you notice first
Whiteflies damage a plant through its sap. Adults and nymphs drink from the phloem, so the plant loses part of what it was using to grow. What you notice first is mottled or yellowing leaves and slower growth, and in a large colony, leaves that dry out and drop. If you have yellow leaves and the undersides are clean, the cause is something else.
Honeydew is the sap they cannot use. It drips onto the leaves below and onto the shelf, and sooty mould grows on it, a black fungus that does not attack the leaf but coats it and blocks light. On a begonia set back from the window, lost growth comes back slowly and the damage stays visible after the insects are gone, which does not mean the treatment failed.
UC IPM records that some species carry viruses into certain vegetable crops, and the University of Wisconsin does not treat it as a major concern. On a houseplant, the damage you will see is the lost sap and the honeydew.
Where whiteflies come from and how they stop coming back
Almost always on a plant. The RHS warns that they are often brought in on new plants, and the other route is a plant coming back indoors after a summer outside. That decides the prevention, and most of it happens before a new plant joins the others.
- Check the undersides before you buy. Disturb the leaves and watch for anything flying up, as the University of Maryland suggests.
- Keep a new plant apart. Leave it away from the rest until you have checked it several times and found nothing, so eggs and nymphs have time to show.
- Look under the leaves when you water. The Missouri Botanical Garden suggests it as a habit, because a whitefly infestation is easiest to remove early.
- Leave a yellow trap up as a warning. When it starts catching adults, a plant nearby has a colony you have not spotted yet.
- Decide about the plant that always has them. UC IPM advises getting rid of a plant that keeps hosting large numbers. Before you do, check in the plant care guide whether it gets the light and water it needs, because a healthy plant recovers faster.
Whitefly eggs and larvae: why they come back after treatment
They come back because the treatment reached the adults and the feeding nymphs, and not the eggs. It also missed the last nymph stage, the one that has settled and stopped moving. That is why a plant looks clear and then fills up again. Check the undersides and treat again as soon as you find nymphs or adults, because that second pass is the one that decides it.
Which plants whiteflies go for, and which to check first
They go for soft-leaved plants and flowering plants. The host lists published by the RHS, UC IPM and the University of Wisconsin agree on poinsettia, hibiscus, fuchsia, geranium and gerbera, and on soft-stemmed indoor flowering plants in general.
A snake plant, with its thick stiff leaves, appears on none of those lists. Check the soft-leaved plants first, then new arrivals and anything that spent the summer outside, and leave the thick-leaved ones for last.
Are whiteflies harmful to humans
No. Whiteflies feed on plant sap, and none of the six sources behind this page describes them feeding on anything but plants. What you will notice is the honeydew, which makes leaves and shelves sticky, and the black sooty mould that grows on it.
Do whiteflies bite humans? None of those sources records a bite on a person or a pet. Their needle-like mouthparts are built to pierce a leaf and draw sap from the phloem, which is where UC IPM describes them feeding.
What eats whiteflies
Lacewings, several small lady beetles, bigeyed bugs, minute pirate bugs and parasitic wasps, according to UC IPM. So do ladybugs eat whiteflies? Some small species do, but on a windowsill that answer changes little. UC IPM calls biological control impractical for a few plants at home, and the RHS adds that a release cannot give instant control, so it has to go in before a plant is heavily affected.
- Lacewings. General predators of soft-bodied insects, and part of what keeps garden outbreaks in check.
- Lady beetles. Several small species feed on them, including the Asian multicoloured lady beetle that UC IPM names.
- Bigeyed bugs and minute pirate bugs. Garden predators that UC IPM says disappear where sprays kill them off, which is when outbreaks start.
- Encarsia wasps. They develop inside the nymphs, which turn black. UC IPM recommends them for greenhouses rather than outdoor use.
What we checked about whiteflies
Everything on this page comes from six sources published by university extension services, a botanical garden and the RHS, and no statement rests on a trial of our own.
Conclusion - whiteflies
Move the plant now, turn it over and look under the leaves. A few adults and no scales means a rinse, a sticky trap and another look when you water. Undersides crowded with nymphs, or honeydew already marking the shelf, means isolating it, treating it and treating again every time a check turns something up.
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