A new invasive alien pest southern armyworm, Spodoptera eridania (Stoll)—has been discovered in four countries in Africa
Farmers in Edo State experienced an outbreak of caterpillars that caused severe defoliation on cassava in a 450-hectare field near Ubiaja in south-eastern Nigeria in mid-December 2016. Alcohol-preserved samples of immatures (larvae) were sent for diagnosis to the Biodiversity Center at the IITA Station in Bénin. They did not match the morphological characteristics of FAW caterpillars. The species appeared to have related origins and closely resembled the African cotton leafworm (Spodoptera littoralis [Boisduval]). In the absence of adult moths it was concluded that the latter species, widespread in tropical Africa and known to feed on various kinds of food, must have attacked some sweet varieties of cassava that are less toxic to potential insect pests. Similar observations were made in early 2017 when farmers submitted alcoholstored samples of immatures for identification following complaints about dense caterpillar colonies in their cassava fields in the areas surrounding Dasso, southern Bénin. Moths were finally obtained from tomato fields attacked in Yaoundé, Cameroon, and samples of adults from the University of Masuku in Franceville, Gabon. The examination of the outer features of the moths together with the genitalia of both sexes allowed an unambiguous identification of the southern armyworm (SAW) Spodoptera eridania (Stoll). As a further means of control, larval and adult samples collected from all present sites were sent to the Germplasm Health, Virology, and Diagnostics Unit at the IITA headquarters in Ibadan for DNA barcode analysis. Results confirmed the findings.