Cutworm

The cut

The name “cutworm” describes exactly what the larva does — it severs plant stems at or just below the soil surface during the night, then retreats underground by day. A cutworm attack is distinctive: the seedling simply falls over, neatly cut, with no other visible damage. The larva has moved on, often to the next plant.

A single larva can destroy a dozen seedlings in one night. In market gardens and field crops, cutworm outbreaks cause economically significant losses.

The species

Many species of noctuid moth produce larvae called cutworms. The most common in Europe are the turnip moth (Agrotis segetum) and the heart and dart moth (Agrotis exclamationis). In North America, the black cutworm (Agrotis ipsilon) is a major corn pest. The adult moths are the classic “brown moth” — well-camouflaged, nocturnal, commonly attracted to light.

Finding them

Because cutworms feed at night and shelter underground by day, they’re rarely seen in the act. Finding them requires digging around the severed plant — the fat, greasy, grey-brown larva will be found curled in a C-shape 3–5 cm below the surface.

Control

• Physical barriers — cardboard collars placed around transplant stems at planting deter surface-feeding species
• Parasitic nematodes (Steinernema carpocapsae) — effective biological control applied to moist soil
• Digging before planting — exposes larvae to birds; a determined robin will follow the spade