Mealy cabbage aphid

Mealy cabbage aphid is common on brassicas. Its presence on established plants can usually be tolerated however, the aphid can make kale inedible and the growth points of young brassica can be severely affected.

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Mealy cabbage aphid

Quick facts

Common name Mealy cabbage aphid
Latin name Brevicoryne brassicae
Plants affected Cabbage, cauliflower, Brussels sprout, swede and other brassicas
Main symptoms Greyish white aphids cluster underneath the leaves and on growing points. Leaves distorted and discoloured on young plants
Caused by A sap-sucking insect
Timing April-October

What is mealy cabbage aphid?

Mealy cabbage aphid is a greenfly with distinct whitish or 'mealy' appearance. They are sap-sucking insects that feed on cabbages and other brassicas.

Symptoms

On first appearances this insect may be confused with cabbage whitefly. However, mealy cabbage aphid does not fly up in a white cloud when disturbed. Other symptoms to look out for include:

  • Dense colonies of greyish-white aphids, up to 2.5 mm long, clustered on the underside of leaves and on the growing points
  • The leaves develop a whitish-yellow discolouration where the aphids are feeding
  • On young plants, the foliage develops in a distorted manner and the growing point may be killed
  • In addition to edible and ornamental brassicas, this aphid can also be found on some related wild plants, such as charlock and shepherd’s purse

Control

Check brassicas frequently from spring onwards so action can be taken before a damaging population has developed, especially more vulnerable young plants. 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 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.

Non-pesticide control

  • Where possible tolerate populations of aphids
  • Use finger and thumb to squash aphid colonies where practical
  • Encourage aphid predators in the garden, such as ladybirds, ground beetles, hoverflies, parasitoid wasps and earwigs. Be aware that in spring aphid populations often build up before natural enemies are active in sufficient numbers and then give good control
  • Dispose of old brassica plants once they have finished cropping to reduce the risk of the next season’s plants becoming affected

Pesticide control

  • 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 aphids. These pesticides have a very short persistence and so may require reapplication to keep aphid numbers in check. Plant oil and fatty acid products are less likely to affect larger insects such as ladybird adults
  • Plant invigorators combine nutrients to stimulate plant growth with surfactants or fatty acids that have a physical mode of action against aphids (e.g. Ecofective Bug Control, RHS Bug and Mildew Control, SB Plant Invigorator and Westland Resolva Natural Power Bug & Mildew). These products contain some synthetic ingredients and so are not considered organic.
  • More persistent contact-action insecticides include the synthetic pyrethroids lambda-cyhalothrin (e.g. Westland Resolva Bug Killer) and deltamethrin (e.g. Provanto Ultimate Fruit & Vegetable Bug Killer, Provanto Sprayday Greenfly Killer).

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 of 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

Download

Pesticides for gardeners (pdf document)

Biology

Mealy cabbage aphid overwinters on its host plants as eggs that are laid on stems in late autumn, although in mild winters active aphids may persist through the winter.

For most of spring and summer, the aphids are present as wingless females that give birth to live young.

Winged forms develop when plants become heavily infested, allowing the aphids to migrate to new host plants.

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