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PestLeaves

Cabbage white caterpillars

The caterpillars of the large and small white butterflies, which can strip a brassica to its midribs in a fortnight. They are conspicuous, easy to find, and almost entirely preventable by keeping the butterflies off the plants.

Caused by: Pieris brassicae and Pieris rapae · also called cabbage worm, cabbage butterfly caterpillars

Described view

A broccoli leaf showing both patterns together: large ragged areas eaten away to the midrib with green-and-yellow cabbage white caterpillars and dark frass pellets still present, and a separate area of the same leaf peppered with the tiny round shot-holes of flea beetle

What brings it on

Adults fly from late spring through summer and lay on the undersides of brassica leaves — the large white in conspicuous yellow batches, the small white singly.

source

Sourced guidancehigh confidence

  • Royal Horticultural Society: Cabbage caterpillars

Checked 2026-08-13

Usually seen: May, June, July, August, September

Preventing it

Ordered by how much difference each measure actually makes, not by how often it is repeated.

  • Cover brassicas with insect-proof mesh before the butterflies are flying, holding it clear of the foliage so eggs cannot be laid through it.
    source

    Sourced guidancehigh confidence

    • Royal Horticultural Society: Cabbage caterpillars — control

    Checked 2026-08-13

  • Check the undersides of leaves weekly through summer. Egg batches removed by hand never become caterpillars.
    source

    Horticultural consensusmoderate confidence

    • UC Statewide Integrated Pest Management Program — University of California Agriculture and Natural Resources: Cole crops — imported cabbageworm monitoring

    Checked 2026-08-13

Dealing with it once it is there

  • Pick caterpillars off by hand. On a garden scale this is genuinely effective, and it is what most growers with a few plants should do.
    source

    Sourced guidancehigh confidence

    • Royal Horticultural Society: Cabbage caterpillars

    Checked 2026-08-13

  • Established plants tolerate a surprising amount of leaf loss. Damage to outer leaves of a heading cabbage rarely affects the head.
    Horticultural consensusDepends on conditionsmoderate confidence

    Applies when: Not true for kale or leafy greens, where the damaged leaves are the crop.

    • UC Statewide Integrated Pest Management Program — University of California Agriculture and Natural Resources: Cole crops — damage thresholds

    Checked 2026-08-13

What it affects

Signs that lead here

Each of these lists the other things that produce the same sign, and how to tell them apart.

On sprays and treatments

GrowingHQ does not tell anyone what to apply, at what rate, or how often. Pesticide approvals differ by country, change without notice, and the product label is legally binding — it is also the document you are holding. What is described here is cultural and physical control, which is what a home grower can act on without a label in front of them.

Plant-specific guides

Where this is one of several causes that look alike on a particular plant, GrowingHQ publishes the differential rather than the general answer.