What does it look like?
Tropical armyworm caterpillar grow to 45 mm long. The colour varies from pale green to dark green to brown as they develop. Mature larvae have three yellow longitudinal stripes with triangular black markings. The caterpillar head of the tropical armyworm has a white 'V'. Caterpillars feed on the foliage of a wide range of plants and crops. The eggs are laid on upper surfaces of the leaves. That distinguishes them from Cosmopolitan armyworm that lay eggs among the stalks of the plants. The wasp, Meteorus pulchricornis lays its eggs in the armyworm and the resulting larvae feed off it as parasites.
Why is it a problem?
Moist, humid and warmer than average temperatures can lead to outbreaks with high numbers of armyworm caterpillars consuming large quantities of pasture and maize crops. Climatic conditions, such as high rainfall/flooding in January and February can disrupt the parasitoid life-cycle (that is, there are fewer of the wasps to feed on the armyworm), reducing their impact on armyworm populations.
Avoid grazing pasture recently infested by armyworm, until the caterpillar feeding cycle has run its course. Armyworm can be controlled using a range of registered insecticides – both synthethic pyrethroid and broad spectrum, if necessary.