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Cutworms: how to recognise and treat it

Pest

Cutworms — Photo: Neil Phillips from uk, CC BY 2.0, Wikimedia Commons

Symptoms

Seedlings and young plants cut off or girdled at or just below soil level, usually overnight.
Holes chewed at night in the leaves of low-growing plants; roots of lettuce, potato tubers and other root vegetables may be eaten.
A plant suddenly wilts and a greyish-brown, sometimes greenish or creamy, caterpillar up to 4 cm long is found curled in a C-shape in the soil beneath it.

Organic treatment

Hand-pick caterpillars at night with a torch, and remove any you find in the soil beneath damaged plants.
Protect seedlings with collars of cardboard or screen around the stems, or with fleece or fine insect mesh.
For larger plants, spray Bacillus thuringiensis (Bt) or water a nematode biocontrol for caterpillars into moist soil at 12–20 °C.

Chemical treatment

Chemical insecticides are not very effective against cutworms and are not recommended for home gardens; where needed, spray spinosad on larger plants and follow the label.

Reference information, not a guarantee. Read and follow the label of any product: dose, safety and the days to wait before harvest.

Prevention

Destroy crop residues and keep the garden free of weeds over winter.
Watch closely in new beds dug from turf or in weedy, overgrown areas, where the moths prefer to lay eggs.
Keep vegetable beds well watered in summer; young caterpillars are very vulnerable to rain and irrigation.
Sow a few more seeds than needed and plant sturdy transplants to allow for some losses.

Sources

Figures checked against these sources.