How to identify and manage cabbage whitefly

UK seasonality and monitoring

Cabbage whitefly is most noticeable in warm summer weather.

During this period inspect Kale, cabbage, sprouts and other brassicas, concentrating on the crop stage and plant parts described above. Note when and where fresh injury appears; old feeding marks can remain after the pest has moved on.

Crops and plants affected

The recorded hosts are Kale, cabbage, sprouts and other brassicas. This list identifies plants worth checking; it does not mean every crop is equally vulnerable. Start with the listed plants and inspect the tissue where this pest feeds.

Check affected crops for these signs: Sap loss, sticky honeydew and sooty mould on older leaves. Match the symptom to a live pest, larva, egg or characteristic feeding sign before deciding that treatment is needed.

Damage and likely consequences

Sap loss, sticky honeydew and sooty mould on older leaves. A small amount of old damage on a vigorous plant may be cosmetic. Continued feeding on roots, seedlings, growing points or edible parts can reduce establishment or yield.

On Kale, cabbage, sprouts and other brassicas, judge severity by checking whether injury is fresh and spreading, whether the plant is still growing, and whether the edible part is affected. Avoid removing a crop based on one ambiguous mark.

Prevention

Check the undersides of brassica leaves for adults and waxy nymphs, and encourage hoverflies and parasitic wasps.

Control and integrated management

Wash small colonies from leaves and judge the plant’s vigour before removing foliage.

Natural predators and wildlife-conscious choices

Tolerate light infestations where plants remain vigorous.

For cabbage whitefly on Kale, cabbage, sprouts and other brassicas, use a barrier or hand removal only where it fits the crop and life stage. Keep any cover taut, inspect it for trapped wildlife, and remove it when protection is no longer needed.

Long-term management

Monitor brassicas in warm weather and leave natural enemies undisturbed where damage remains light.

For cabbage whitefly on Kale, cabbage, sprouts and other brassicas, record the bed, crop stage and date when fresh damage first appears. Those notes help time protection and monitoring before the same crop stage is vulnerable next season.

Common mistakes

A symptom alone is not a diagnosis. Tiny white adults flutter from brassica leaves when disturbed; flat, pale nymphs and waxy deposits remain underneath. It is usually a nuisance on older leaves rather than a reason to remove a healthy plant. Look for a matching live pest or fresh feeding sign before intervening.

Cabbage whitefly is not the same as greenhouse whitefly; consider the host and growing conditions.

If damage continues

Recheck Kale, cabbage, sprouts and other brassicas where new injury is appearing, including the hidden feeding site: roots, folded leaves, leaf undersides, flowers or fruit as appropriate. If identification remains uncertain, photograph a live specimen alongside the damage and ask an allotment association or horticultural adviser.

If the recommended control (Wash colonies from leaves and remove heavily infested foliage.) has not helped, confirm that it was fitted or applied at the right crop stage and that fresh damage is still occurring. Old marks do not heal when the pest has gone.

Frequently asked questions