Cutworms
Agrotis infusa; Agrotis munda; Agrotis ipsilon
Fat soil-dwelling caterpillars that chew through seedling stems at ground level, often overnight.
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Identify from a photoBackground
Cutworms are the larvae of several native and introduced Agrotis moths. They hide in the top few centimetres of soil during the day and come out at night to feed. Their signature damage is young seedlings cut off cleanly at or just above soil level, left to wilt on the surface. A single caterpillar can destroy a whole row of new transplants in one night.
How to identify
- Larvae: plump grey-brown to nearly black caterpillars, 25-40mm when full grown, curl up into a C-shape when disturbed
- Pupae: brown, found in soil
- Adults: brown or grey moths with forewing wingspan 35-45mm (Bogong moth is Agrotis infusa)
- Damage: seedlings felled at soil level, overnight
Life cycle
Eggs laid in soil or on low plants in spring and autumn. Larvae feed for 4-6 weeks before pupating in soil. Adults emerge after 2-3 weeks. Two or more generations per year.
Weather triggers
- Temperature: 10-30°C
- Damage is worst on newly cultivated beds that were previously weedy. Heavy autumn rains bring the next generation to the surface.
Peak season (southern hemisphere)
Red = active season · Dark red outlined = this month
Affected vegetables & crops
Click any crop to see current prices and growing info.
Climate zones at risk
Organic & low-impact control
- Cardboard or plastic collars sunk 2-3cm around seedling stems
- Hand hunting at night with a torch. Caterpillars are easy to spot feeding on seedlings
- Bacillus thuringiensis (Btk) sprayed onto foliage in the evening
- Encourage predatory beetles and birds by keeping some ground cover nearby
Chemical control
- Carbaryl bait pellets are still registered in some states but not recommended for home gardens due to non-target impact
- Spinosad-based sprays are effective and have a lower non-target footprint
Always read product labels. Registrations change.
Prevention
- Keep beds weed-free for 2-3 weeks before planting. Cutworms are often already in the soil
- Plant stronger transplants rather than direct-seeded seedlings where cutworm pressure is high
- Cultivate the top few centimetres of soil at night to expose larvae to birds
Companion planting
No specific companion plant repels cutworms. Dense ground cover actually gives them shelter, so bed preparation matters more than planting mix.
Biosecurity
Native and widespread. No quarantine concern.
Know when Cutworms is actually about
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