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 plants can be severely affected.
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
What is mealy cabbage aphid?
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
- On most brassicas these insects can be tolerated and are a food source for many aphid predators, which can wipe out aphid colonies. On kale and young plants palatability and growth can however be affected.
Check brassicas frequently from spring onwards so action can be taken before a damaging population has developed, especially on more vulnerable young plants and kale. On older established plants this aphid can usually be tolerated and is a food source for many other invertebrates. 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.
- Where possible tolerate populations of aphids they form an important part of many food chains and can be part of a healthy garden ecosystem
- 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 controlThe RHS believes that avoiding pests, diseases and weeds by good practice in cultivation methods, cultivar selection, garden hygiene and encouraging or introducing natural enemies, should be the first line of control. If chemical controls are used, they should be used only in a minimal and highly targeted manner.
- 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. 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), deltamethrin (e.g. Provanto Ultimate Fruit & Vegetable Bug Killer, Provanto Sprayday Greenfly Killer) and cypermethrin (e.g. Py Bug Killer)
- A systemic containing the active ingredient Flupyradifurone (Provanto Smart Bug Killer) is available for use on ornamentals and selected edibles
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
Pesticides for gardeners (pdf document)
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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