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 infestations can usually be tolerated.
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.
Where possible tolerate the prescence of cabbage whitefly.
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.
- Organic sprays, such as natural pyrethrum (e.g. Bug Clear Gun for Fruit & Veg, Ecofective Bug Killer), fatty acids (e.g. Solabiol Bug Free, Doff Greenfly & Blackfly Killer) or plant oils (e.g. Vitax Organic 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 insects 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 can 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
- Inclusion of a pesticide product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener
- Do not spray on or near plants in flower due to the danger to pollinating insects
Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)