Black cutworm (Agrotis ipsilon), Lepidoptera

Black cutworm biology & life cycle

Cutworm moths do not over-winter in Ontario but are carried in from the south on strong southerly weather systems. The heaviest immigration occurs from April to May but may occur as early as March. Cutworms are therefore more frequent in fields with green cover early in the spring. There are several generations per year, however, only the first generation causes economic damage in corn. Warm, clear, calm nights in early spring are ideal for moths to lay eggs. Eggs are laid on dense vegetation, low to the ground, and are usually laid before primary tillage in the spring. In fields with vegetation present before planting, larvae will develop on the weeds until the crop has emerged. In this situation, the larvae that move over to the crop will be larger and more difficult to control. Feeding occurs from early May through to mid-June. (source: OMAFRA)

Identifying Black cutworm

Black cutworm: larvae

The black cutworm larvae can range from light gray to nearly black in color, with a brown head capsule and black spiracles. A yellowish stripe runs the length of the back. It is also often referred to as the greasy cutworm. Larvae can grow to a length of 30-45 mm in length when mature. Pupae are brown and 17-22 mm long.

Black cutworm: adult

Black cutworm adult moths are dark, about 38 mm long, with a black dagger-shaped mark near the outer edge of the forewing.

Black cutworm: management

OMAFRA supplies the following management strategies:

Foliar insecticide treatment is most effective when applied to the soil soon after cutworms have hatched. Cutworms are most active in the evening, so insecticides applied at night/evening are more effective. Foliar insecticide application to mature larvae (larger than 2.5 cm or 1 in.) is not recommended since most of the damage has occurred and control may be inadequate.
In no-till corn fields, it is important to remove green vegetation that could attract the moths in early spring. Fall burndown of volunteer crops and weeds is recommended. Fields should be bare for at least 2-3 weeks before planting.