Genetic studies of fall armyworm indicate a new introduction into Africa and identify limits to its migratory behavior

Authors: Nagoshi, Rodney; GOERGEN, GEORG - International Institute Of Tropical Agriculture (IITA); KOFFI, DJIMA - University Of Lome; AGBOKA, KOMI - University Of Lome; ADKEVO, ANANI - University Of Lome; DU PLEISSIS, HANNALENE - North-West University; VAN DEN BERG, JOHNNIE - North-West University; TEPA-YOTTO, GHISLAIN - International Institute Of Tropical Agriculture (IITA); WINSOU, JEANNETTE - Norwegian University Of Life Sciences; Meagher, Robert - Rob; BREVAULT, THIERRY - Cirad, France

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2022
Publication Date: 2/4/2022
Citation: Nagoshi, R.N., Goergen, G., Koffi, D., Agboka, K., Adkevo, A., Du Pleissis, H., Van Den Berg, J., Tepa-Yotto, G., Winsou, J., Meagher Jr, R.L., Brevault, T. 2022. Genetic studies of fall armyworm indicate a new introduction into Africa and identify limits to its migratory behavior. Scientific Reports. 12, Article No. 1941. https://doi.org/10.1038/s41598-022-05781-z.
DOI: https://doi.org/10.1038/s41598-022-05781-z

Interpretive Summary: The fall armyworm is major insect pest of corn and other crops. Originally found in South America and in portions of the southeastern United States fall armyworm has spread across the globe with severe outbreaks reported throughout sub-Saharan Africa, posing a significant threat to African agriculture. Scientists from USDA-ARS, Gainesville, FL, collaborated with African researchers to genetically analyze fall armyworm populations from 22 sub-Saharan African nations. The results show that a second entry of fall armyworm likely occurred in west Africa from a source different than that of the original introduction. These findings indicate that west Africa continues to be at high risk of future introductions of fall armyworm, which could complicate mitigation efforts.

Technical Abstract: The fall armyworm, Spodoptera frugiperda (J.E. Smith) is native to the Americas and a major pest of corn and several other crops of economic importance. The species has characteristics that make it of particular concern as an invasive pest, including broad host range, long-distance migration behavior, and a propensity for field-evolved pesticide resistance. The discovery of fall armyworm in west Africa in 2016 was followed by what was apparently a remarkably rapid spread throughout sub-Saharan Africa by 2018, causing economic damage estimated in the tens of billions USD and threatening the food security of the continent. Understanding the history of the fall armyworm invasion of Africa and the genetic composition of the African populations is critical to assessing the risk posed to different crop types, the development of effective mitigation strategies, and to make Africa less susceptible to future invasions of migratory moth pests. This paper tested and expanded on previous studies by combining data from 22 sub-Saharan nations during the period from 2016-2019. The results support initial descriptions of the fall armyworm invasion, including the near absence of the strain that prefers rice, millet, and pasture grasses, while providing additional evidence that the magnitude and extent of FAW natural migration on the continent is more limited than expected. The results also show that a second entry of fall armyworm likely occurred in west Africa from a source different than that of the original introduction. These findings indicate that west Africa continues to be at high risk of future introductions of FAW, which could complicate mitigation efforts.