Whitefly: identify, prevent, control

Updated June 2026

Worst in warm weather and under glass, peaking spring through autumn, September to April.

Whiteflies are tiny white sap-sucking insects that rise in a cloud when disturbed. They cluster on leaf undersides of tomatoes, beans and brassicas, weaken plants, spread viruses and coat leaves in honeydew and sooty mould.

How to identify it

• Clouds of tiny white insects flying up when you brush the plant
• Tiny white insects and pale scale-like nymphs on leaf undersides
• Yellowing, weakened leaves and stunted growth
• Sticky honeydew and black sooty mould on lower leaves

How to prevent it

• Inspect and isolate new seedlings, a common way whitefly arrives
• Avoid heavy nitrogen feeding that fuels the soft growth they prefer
• Hang yellow sticky traps early to monitor and catch adults
• Encourage lacewings and tiny parasitic wasps by keeping flowering plants nearby

Organic control, step by step

• Vacuum or hose adults off in the cool of the morning when they are sluggish
• Spray eco-oil or soap spray onto leaf undersides where they gather
• Repeat sprays every 5 to 7 days to catch newly hatched nymphs
• Use eco-neem for heavier infestations to disrupt breeding
• Hang yellow sticky traps among plants to trap flying adults
• Remove and bin badly infested lower leaves

Plants it attacks