Army cutworm (Euxoa auxiliaris), Lepidoptera

Army cutworm biology & life cycle

Adult moths emerge in June and take shelter to escape summer heat. They re-emerge in September and lay eggs in or on the soil during fall afternoons. Eggs hatch when fall moisture conditions are favourable. The larvae do little damage in the fall and overwinter in soil. Larvae resume feeding in spring and this is when damage occurs. Feeding is done entirely above ground and after the leaves are removed from one plant, the larvae will move to adjacent plants. Feeding is usually done late afternoon or early evening. Outbreaks are correlated with a dry July and wet fall.

One generation per year.

Identifying Army cutworm

Army cutworm: larvae

Larvae are pale green-gray to brown in color with the back pale striped and finely mottled with white and brown. The head is light brown with small dark spots. Full-grown larvae may reach 1.5 inches.

Army cutworm: Pupae

Pupae are found in the soil, are dark brown in color and are indistinguishable from those of other cutworms.

Army cutworm: adult

Adult moths are 0.8 inches long with a wingspan of 1.5-1.75 mm. They are gray-brown "miller" moths with two prominent spots on the forewing.

Army cutworm: management

Scout fields, especially in early spring prior to green-up, and look for these larvae in the soil. In fields where stands are thin and poorly tillered, 1 or 2 army cutworms per square foot may justify treatment. With vigorous wheat stands, treatment is usually not necessary until populations average 4 to 5 worms per square foot. It is important to detect and control army cutworms while they are small, before they cause significant crop losses.

Manage preventatively with seed treatment insecticides registered for cutworm. Foliar insecticide treatments may be warranted if economic thresholds are exceeded.