Caterpillars
Moth and butterfly larvae chew leaves, and some tunnel into fruit and heads. Cabbage white caterpillars strip brassicas in summer; others attack peas, corn, grapes and herbs. Most are easy to pick off once found.
Pests
What it looks like
Droppings are as telling as the holes.
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Chewed holes Irregular holes in leaves, sometimes only veins left. -
Green droppings Small dark green pellets on leaves and in the heart. -
Egg clusters Yellow eggs in clusters under brassica leaves. -
Tunnels Holes into cabbage hearts, cobs and pea pods.
How to confirm it
Look for the culprit.
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Search leaf undersides
Caterpillars and eggs hide under leaves and in the hearts.
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Look for droppings
Fresh droppings mean an active feeder above.
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See butterflies
White butterflies around brassicas mean eggs soon.
What to do
Pick them off and keep butterflies out.
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Hand-pick
Check every few days and pick off caterpillars and egg clusters.
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Net brassicas
Cover with fine netting, supported clear of the leaves, from planting.
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Bt spray
Bacillus thuringiensis targets caterpillars if numbers are high.
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Leave some for wildlife
On herbs like dill, swallowtail caterpillars are welcome visitors.
Prevent it next time
- Net brassicas all summer.
- Encourage birds and parasitic wasps.
- Rotate crops and clear old plants.
What not to do
Do not spray broad-spectrum insecticides on flowering herbs; they kill pollinators and parasitoids.
In the growing guides
Where the guides mention it, with plant-specific advice.
Sources
- Cabbage caterpillars, Royal Horticultural Society
- Imported cabbageworm on vegetables, University of Maryland Extension