Cabbage whitefly can be difficult to control, particularly on allotments where there are likely to be affected plants on nearby plots that will be a source of re-infestation. Fortunately, cabbage whitefly only affects outer leaves and usually causes little real damage to parts of the plant that are consumed, therefore populations can usually be tolerated.
Check susceptible plants frequently from spring onwards so action can be taken before a damaging infestation has developed. When choosing control options you can minimise harm to non-target animals by starting with the methods in the non-pesticide control section. If this is not sufficient to reduce the damage to acceptable levels then you may choose to use pesticides. Within this group the shorter persistence pesticides (that are usually certified for organic growing) are likely to be less damaging to non-target wildlife than those with longer persistence and/or systemic action.
Where possible tolerate the presence of cabbage whitefly, with the exception of Kale it does not normally affect edible parts.
Cabbage whitefly is not attacked by the biological control, Encarsia formosa parasitoid sold for use against glasshouse whitefly (Trialeurodes vaporariorum) but there are some other Encarsia species that occur naturally in Britain that develop as larvae in cabbage whitefly nymphs. They are not commercially available but are sometimes sufficiently numerous to be effective at keeping cabbage whitefly at a low level. The use of relatively persistent pesticides, such as deltamethrin or lambda-cyhalothrin, will be harmful to these parasitoids and may allow a resurgence in the whitefly population that is able to reproduce without its numbers being reduced by these natural enemies.
The immature stages are not very susceptible to insecticides and so several applications may be needed to reduce a heavy infestation. Complete eradication is neither feasible nor necessary as it is only heavy infestations that are likely to cause problems with sooty mould. Brassica leaves are waxy and this makes them difficult to wet with pesticide sprays. Kale is the plant most affected as this insect occurs on young leaves that are going to be eaten. On cabbage, sprouts, cauliflower and broccoli, the edible parts are little affected.
- Organic sprays, such as natural pyrethrum (e.g. Bug Clear Gun for Fruit & Veg, Neudorff Bug Free Bug and Larvae Killer), fatty acids (e.g. Solabiol Bug Free, Doff Greenfly & Blackfly Killer) or plant oils (e.g. Vitax Plant Guard Pest & Disease Control, Bug Clear for Fruit and Veg) can give good control of cabbage whitefly. These pesticides have a very short persistence and so may require reapplication to keep the insect in check. Plant oil and fatty acid products are less likely to affect larger insects such as ladybird adults. The organic pesticides are not restricted in number of applications and could be used up to one day before eating the produce
- More persistent insecticides include the synthetic pyrethroids lambda-cyhalothrin (e.g. Westland Resolva Pest Killer), deltamethrin (e.g. Provanto Ultimate Fruit & Vegetable Bug Killer) and cypermethrin (e.g. Py Bug Killer). Two (in some cases three) applications of cypermethrin, deltamethrin or lambda-cyhalothrin can be used per crop and there is a 7 or 14 day harvest interval
Follow label instructions when using pesticides. On edible plants make sure the food plant is listed on the label and follow instructions on maximum number applications, spray interval and harvest interval
Plants in flower should not be sprayed due to the danger to bees and other pollinating insects
Inclusion of a pesticide product does not indicate a recommendation or endorsement by RHS Gardening Advice. It is a list of products currently available to the home gardener
Pesticides for gardeners