The fall armyworm is a polyphagous pest that is indigenous throughout the Americas. Recently, it has been found in Africa too. The caterpillars of fall armyworms feed on the leaves, stems and reproductive parts of more than 100 plant species causing major damage to cultivated grasses, such as maize, rice, sorghum and sugarcane, as well as other crops, including cabbage, beet, peanut, soybean, alfalfa, onion, cotton, pasture grasses, millet, tomato, potato and cotton.
Fall armyworm moths generally disperse in a radius of about 500 km (300 miles) before oviposition, which is sufficient for them to move from seasonally dry habitats to wet habitats in Central America. This makes it possible for fall armyworms to spread over large areas rapidly. Adults fly by night, and are attracted to lights, especially those with a strong ultra-violet component.
Life cycle of the Fall Armyworm
Adult moths are 20 to 25 mm long and have a wingspan of 32-38 mm. They are nocturnal and most active during the warm, humid evenings. Females lay their eggs in clusters of 150-200 and can lay up to 2000 eggs in a lifetime. Eggs are white, pinkish or light green and spherical, and are usually laid on the underside of the leaves. The larvae (caterpillars) are 30-40 mm long. They have six instars that vary in colour from light tan to green to black. They have a distinct white inverted Y-shaped mark on the front of the head and four large spots on the upper surface of the last segment. Pupae are reddish brown and measure 13 to 17 mm in length. The eggs hatch after 3-5 days. Over the next 2 to 3 weeks, the larvae pass through 5-6 stages and the pupal stage takes 9-13 days
The developing larvae eat different parts of the host plant, depending on the crop, the stage of crop development, and the age of the larvae. On maize, young larvae usually feed on leaves, creating a characteristic windowing effect. This damage and moist sawdust-like frass near the funnel and upper leaves can be an easily spotted sign of larval feeding. After feeding, the leaves appear ragged or torn (similar to hailstorm damage in appearance).