Scientific name: Spodoptera exempta (Walker)
Common name: African Armyworm
Synonyms: Laphygma exempta (Wlk.)
Ethiopian name: Temch
Main hosts: Grasses, Maize, Sorghum, Tef, Rice
Alternative hosts: Many species of cereals and wild grasses
IMPORTANCE IN ETHIOPIA:
During outbreaks a major pest of: Barley, Maize, Sorghum, Tef, Wheat
DISTRIBUTION IN ETHIOPIA:
Outbreaks usually start during May in the southern provinces. During the main growing season they move northwards.
The caterpillars feed on the leaves eating them down to the midrib.
INSECT BIOLOGY & RECOGNITION:
Egg: The eggs are laid in groups of 100-400. A female lays several egg masses until a total of up to 1000 eggs. The eggs are laid in single or multi layers on the leaves. They are covered with black hair scales. When they are laid, the colour of the eggs is yellowish. Just before hatching they turn black. The diameter of the eggs is about 0.5 mm. Hatching takes place after 2-4 days.
Pupa: The mature caterpillars burrow into the soil. They pupate in chambers 2 3 cm below the surface. The pupa is brown or black in colour. It is about 17 mm long. The pupal period takes 7 12 days.
Adult: The adult is a grey brown night flying moth. The wingspan is 20 35 mm for males and 22 37 mm for females. The hind wings are pale white with dark veins. The forewings are dull grey brown. They have two spots. The inner (orbicular) spot is elongate and pale. The outer (reniform) spot is kidney shaped and more clearly visible in males than in females. The moths are attracted by lights at night.
A related species, Spodoptera exigua (Lesser Armyworm) feeds not only on Gramineae but also on many other crops, including cotton, tobacco, tomato, groundnut and beans. Unlike S. exempta, this species does not migrate over long distances, but the caterpillars are gregarious and move in swarms. The grey brown adult moth is 12 15 mm long and has a wingspan of about 25 mm. The hind wings are white with grey brown margins.