Cabbage caterpillars

Cabbages and other brassicas can be extensively holed by caterpillar feeding 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 Brussels sprout, some ornamental plants in the Cruciferae family, 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. Large cabbage white butterfly caterpillars are yellow and black with obvious hairs on their bodies (see picture above). Those of 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.

    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.

    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 are 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.

    Control

    Non-chemical control

    • Inspect plants regularly and pick off the pale yellow butterfly eggs, white spherical moth eggs and caterpillars when seen
    • 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.
    • A biological control is available for caterpillars, this is supplied as a mixture of pathogenic nematodes, (sold as Fruit and Vegetable Protection), 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

    Chemical control

    • On food plants 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
    • A wide range of brassicas can be sprayed with the contact pyrethroid insecticides deltamethrin (e.g. Bayer Provado Ultimate Fruit & Vegetable Bug Killer), lambda-cyhalothrin (e.g. Westland Resolva Bug Killer), cypermethrin (e.g. Py Bug Killer) or pyrethrum (considered organic e.g. Bug Clear Gun for Fruit & Veg, Ecofective Bug Killer (also contains fatty acids))
    • 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. The organic pesticide pyrethrum is not restricted in number of applications and could be used up to one day before eating the produce
    • 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 the RHS. It is a list of products currently available to the home gardener

    Downloads

    Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)

    Biological control suppliers (Adobe Acrobat pdf document listing biological controls available to gardeners).

    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

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