Pests

Whitefly

Tiny white moth-like insects that rise in a cloud when leaves are brushed.

What you'd see

A puff of small white insects when the plant is touched
Pale, flat, oval scales (nymphs) on leaf undersides
Honeydew, sooty mould and yellowing leaves

Where to look

Undersides of leaves; herbs, hibiscus, fuchsia and pelargoniums indoors are favourites.

How it spreads

Adults fly readily between plants; eggs are laid in circles on undersides.

Is it really this? Look-alikes

Fungus gnats — Gnats are dark and come from the soil; whitefly are white and come from leaves.
Mealybugs — Mealybugs do not fly.

What's going on

Whitefly are sap-sucking relatives of aphids and scale. The nymph stage is stationary on the leaf underside, feeding and coating itself in wax; the adult flies.

They breed continuously in warm rooms — there is no winter pause indoors.

Why?

The flying adult is what you notice; the stationary nymph is what you must treat. That is why sticky traps plus repeated undersides spraying is the pattern.

Grandmother's remedies

What people have always done — with an honest note on each.

The vacuum trick
Early morning when they are sluggish, gently vacuum adults off the plant.
Verdict: Odd but effective at thinning adults. Empty the bag outside.
Soapy underside wipe
Wipe nymphs from undersides with soapy water and a cloth.
Verdict: Effective and necessary; adults alone are only half the population.

Modern remedies

What growers and extension services reach for today.

Yellow sticky cards
Hung just above the plant.
Verdict: Very effective for adults.
Insecticidal soap or horticultural oil
Undersides, every 5–7 days for three or four rounds.
Verdict: Works on nymphs and eggs with good coverage.
Encarsia formosa (parasitic wasp)
Released in greenhouses.
Verdict: Gold standard in glasshouses; not practical for a windowsill.

Honest verdict

Whitefly is manageable but stubborn indoors because breeding never pauses. Persistence over a month is the whole method.

Prevention

Yellow sticky card near susceptible plants
Inspect undersides of herbs and flowering plants
Isolate new arrivals