Caterpillars: damage and safe control

Caterpillars are the larvae of moths and butterflies. In the veggie patch the usual culprit is the cabbage white, whose green caterpillars love brassicas such as cabbage, broccoli, kale and cauliflower.

How to spot them:

1. Ragged holes chewed through leaves, often between the veins.
2. Green or brown grub-like insects on the leaves, frequently on the underside.
3. Small dark droppings (frass) on leaves and on the ground below.
4. White or yellow butterflies fluttering around your brassicas, which are laying the next lot of eggs.

The damage they do: caterpillars can strip young plants fast, chewing leaves, stems and sometimes fruit. Seedlings are especially at risk.

How to manage them, safely:

1. Net your brassicas. Fine insect netting stops the butterflies laying in the first place, and is the single best fix.
2. Pick them off. Check the underside of leaves every few days and remove caterpillars and eggs by hand.
3. Encourage the predators. Birds and small parasitic wasps feed on caterpillars, and a varied, flowering garden (see companion planting) brings them in.
4. Use Bacillus thuringiensis (Bt) if needed. Bt targets caterpillars specifically and is safe on food plants, bees and pets. Neem oil is another garden-safe option.

We do not recommend harsh synthetic insecticides on food crops. Bt and netting handle caterpillars without the collateral damage. For the full picture, see our guide to managing pests safely.

Plan your patch: our free planting calendar shows what to plant now where you live. Ready to grow? Browse our raised garden beds or build your own with the garden bed builder.

Image: CC BY 3.0, via Wikimedia Commons.