Cabbage caterpillars

Cabbages and other brassicas are a favourite food source of a number of caterpillars, and can be extensively holed by the end of summer.

Large cabbage white butterfly (Pieris brassicae) on Cabbage (Brassica sp.). Credit: RHS/Science.

Quick facts

Common names Large cabbage white, small cabbage white and cabbage moth
Scientific names Pieris brassicae, Pieris rapae, Mamestra brassicae
Plants affected All brassicas, including cabbage, broccoli and sprouts; some ornamental Cruciferae and nasturtiums
Main symptoms Holes in the leaves and presence of caterpillars
Most active May-October

What are cabbage caterpillars?

Caterpillars are the larval stage of various butterflies and moths. There are several species of caterpillar that feed on cabbages, other brassicas and other plants including turnip, swede, horseradish and nasturtiums.

There are three common caterpillar culprits:

  • Large cabbage white butterfly (Pieris brassicae)
  • Small cabbage white butterfly (Pieris rapae)
  • Cabbage moth (Mamestra brassicae)

All three may be present at the same time. Caterpillars of cabbage moth and small white butterfly can be more damaging as they bore into the hearts of cabbages, whereas the yellow and black caterpillars of the large cabbage white stay mostly on outer leaves.

Symptoms

Holes are eaten in the outer leaves of all brassicas and damage may also be seen on the inner leaves of cabbages when the heart is cut through. Caterpillars and their excrement are often found on the plants.
 

  • Large cabbage white butterfly caterpillars are yellow and black with obvious hairs on their bodies (see picture above)
  • Small cabbage white butterfly are pale green and covered in short, velvet-like hairs
  • Cabbage moth caterpillars are yellowish green or brownish green, with no obvious hairs on their bodies

Control

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.


Non-pesticide control

  • Where possible tolerate populations as cabbage caterpillars are food for many other creatures including social and parasitoid wasps and birds. Large cabbage white caterpillars are often infected with the parasitoid Cotesia glomerata, the larvae of this wasp burst out of the caterpillar and spin yellow cocoons
  • Growing brassicas under fine netting or horticultural fleece can exclude adult butterflies and moths from laying eggs on the crop. Care must be taken to ensure the netting does not touch the plants or the adults can lay eggs through it
  • Inspect plants regularly and pick off the pale yellow butterfly eggs, white spherical moth eggs and caterpillars when seen
  • A biological control is available for caterpillars, this is supplied as a mixture of pathogenic nematodes, (sold as Nemasys Fruit and veg nematodes), suppliers of which can be found in the biological control leaflet available from the downloads section below. The longer the treated caterpillars and foliage stay wet, the greater chance of the treatment being effective, so apply during cool dull/ damp weather

Pesticide control

If treating food plants with pesticides ensure that the crop is listed on the pesticide label and that all instructions are followed, particularly those on harvest interval, spray interval and maximum number of applications.
  • Organic contact insecticides containing natural pyrethrins (e.g. Bug Clear Gun for Fruit & Veg, Neudorff Bug Free Bug and Larvae Killer) can give good control of cabbage caterpillars. These pesticides have a very short persistence and so may require reapplication to keep the insects in check. 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 Bug 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
Plants in flower should not be sprayed due to the danger to 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
 

Downloads

Pesticides for gardeners (link downloads pdf document outlining pesticides available to gardeners)

Biological control suppliers (downloads pdf document)

Biology

  • The adult butterflies and moths lay eggs on brassica leaves. Large white butterflies lay clusters of yellow, skittle-shaped eggs on the top or bottom surface of leaves. Small white butterflies lay yellow eggs singly on the underside of leaves. Cabbage moth lays white spherical eggs in clusters on either surface of leaves
  • The butterflies have two generations during the summer; cabbage moth has two or three overlapping generations
  • Large and small white caterpillars are likely to be seen in June-July and August-September; cabbage moth caterpillars are active in July-September
  • When fully fed, the caterpillars leave the plants to pupate. Cabbage moth pupates and overwinters in the soil and cabbage white butterfly larvae pupate on suitable vertical surfaces above ground level


Gardeners' calendar

Find out what to do this month with our gardeners' calendar

Advice from the RHS

Did you find the advice you needed?

RHS members can get exclusive individual advice from the RHS Gardening Advice team.

Join the RHS now

Get involved

The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.