Tropical Armyworm Moth (Spodoptera litura) — identification, habitat & look-alikes

The tropical armyworm is a moth whose caterpillars are among Asia's most destructive crop pests, feeding on more than 100 kinds of plants. In the US it is recorded only from Hawaii, and the US is one of many countries that list it as a . It is also called the tobacco cutworm or cotton leafworm.

Appearance

Appearance: A gray-brown moth with a wingspan of about 1.2–1.6 in (30–40 mm). The forewings are busily patterned in gray to reddish brown, with pale streaks along the veins; the hindwings are grayish white with gray edges.

Look-alikes

Egyptian cotton leafwormSpodoptera littoralis

Adults and caterpillars look almost the same. The tropical armyworm usually has darker, contrasting veins on the hindwing, but a reliable ID needs an expert to examine the genitalia under a microscope.

Why they get mixed upA close relative from Africa, the Middle East, and southern Europe that eats the same wide range of crops.

Where it lives

Typical habitats: farm fields
vegetable gardens
greenhouses
Range: South, Southeast, and East Asia, Australia, New Zealand, and many Pacific islands. In the US it is recorded only from Hawaii.
Preferred conditions: It can't survive freezing winters, which helps keep it out of colder regions.

Behavior

Diet: Caterpillars eat leaves of tobacco, cotton, soybeans, cabbage and other brassicas, peppers, sweet potatoes, peanuts, and many ornamentals.
Activity: Caterpillars feed at night and hide in the soil by day. In warm tropical climates there can be 8 to 12 generations a year.

Life cycle

Reproduction: Females lay several hundred eggs in a clump and cover them with hairlike scales. Caterpillars pupate in the soil near the base of the plant.
Larva: Caterpillars grow to about 1.6–1.8 in (40–45 mm) and range from dark green to reddish brown or blackish gray, with a pair of dark half-moon spots on each abdominal segment.