Whitefly
Pest · Commonly affects: Tomatoes, Cucumbers, Aubergines, Fuchsias, Poinsettias, Kale, Brussels sprouts, Cabbages
Whitefly includes glasshouse and brassica whitefly, both common sap-feeding pests in UK gardens. They thrive where plants are crowded or sheltered, especially under glass, but brassica whitefly also persists outdoors. Their feeding weakens foliage and leaves honeydew that can make ornamental and edible plants look grubby and unhealthy.
How to identify it
Disturb a leaf and small white insects, about 1 to 2 mm long, rise in a brief cloud before settling beneath foliage again. Adults resemble tiny white moths, while flattened pale scales or nymphs cling to leaf undersides. Look for sticky honeydew, black sooty mould and yellowing leaves. Glasshouse whitefly is common on tender plants under glass; brassica whitefly is often found in dense colonies on kale, sprouts and other brassicas.
Damage
Whitefly removes sap, leading to yellowing, reduced vigour and premature leaf drop on heavily affected plants. Honeydew coats leaves and supports sooty mould, which reduces their ability to capture light. On edible brassicas, colonies and mould can make harvested leaves unappealing. Infestations spread readily between closely packed plants, especially in a warm glasshouse.
Prevention
Inspect the undersides of leaves before buying or moving plants indoors, and isolate suspect plants from healthy ones. Keep glasshouses ventilated, remove weeds and old leaves, and avoid overcrowding. Space brassicas sufficiently for air movement and clear crop debris after harvest. Use yellow sticky traps under glass to monitor adults early. Encourage hoverflies, lacewings and other beneficial insects outdoors, and choose robust, well-grown plants rather than stressed specimens.
How to manage it
Remove the worst-infested leaves and dispose of them in household waste, then wash honeydew from accessible foliage. Gently tap or vacuum adults from sturdy plants early in the day, repeating often enough to interrupt breeding. Use yellow sticky traps under glass to reduce and monitor flying adults. In enclosed glasshouses, the parasitic wasp Encarsia can provide biological control. Keep checking leaf undersides, as nymphs remain attached after adults have been disturbed.
Whitefly: frequently asked questions
How do I identify whitefly?
Disturb a leaf and small white insects, about 1 to 2 mm long, rise in a brief cloud before settling beneath foliage again.
How do I prevent whitefly?
Inspect the undersides of leaves before buying or moving plants indoors, and isolate suspect plants from healthy ones.
How do I get rid of whitefly?
Remove the worst-infested leaves and dispose of them in household waste, then wash honeydew from accessible foliage.
General guidance for UK home gardens and allotments, focused on prevention and non-chemical control. For a confirmed diagnosis, the RHS or a local garden centre can help. Page updated 19 Sep 2026.