ABOUT THE AFRICAN ARMYWORM
The African armyworm, scientifically known as Spodoptera exempta, is a species of moth in the family Noctuidae, whose larvae are known for their destructive feeding habits on a variety of grasses and early stages of cereal crops such as corn, rice, wheat, millet, and sorghum.
These caterpillars are particularly notorious for their marching behaviour as they move in large groups to feeding sites, a characteristic that has earned them the moniker “armyworm.” The larvae exhibit a fascinating form of polyphenism; when raised in isolation, they are green, but those raised in groups turn black, with the latter phase, known as gregaria, being especially harmful to vegetation.
African armyworms are commonly found across the African continent, with a presence also noted in Yemen, some Pacific islands, and parts of Australia. They are migratory pests and can cause significant damage to crops in plague years. The life cycle of the African armyworm is alarmingly rapid, with only about ten days between hatching and pupation. This swift growth and reproduction rate enable them to wreak havoc on agricultural lands in a short period. The larvae are the most damaging stage of the armyworm’s life cycle, voraciously consuming plant material and increasing their feeding rate as they develop over two to three weeks. Outbreaks of African armyworms are a major concern for staple crops and pasture grasses in sub-Saharan Africa, with the majority of incidents reported on the eastern half of the continent, particularly in countries like Tanzania and Kenya. These outbreaks are considered a serious problem almost every year, and in major outbreak years, the armyworms can affect millions of hectares, leading to massive losses not only to staple grain crops but also to pasture and livestock production.
Adult moths play a crucial role in the spread of the pest due to their highly migratory nature. The timing, location, and magnitude of armyworm outbreaks are difficult to predict, much like the infamous desert locust, which adds to the challenge of managing this pest. Adult moths can migrate over long distances, and their ability to fly further with favourable winds makes it even more challenging to control their spread.
The recent outbreaks in southern Africa have been attributed to a combination of the native African armyworm and a new invasive species, the Fall armyworm. The latter is endemic to tropical and subtropical regions of Central and South America and has been causing considerable damage to maize and other crops since its arrival on the African continent. The Fall armyworm’s presence in Africa was first identified in 2016, and it has since spread rapidly across the continent. The infestation of African armyworms is a significant agricultural concern due to their potential to cause food shortages and economic distress for communities dependent on farming.
- Additional information sourced online