The Noctuid moth fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) is a native of the Western Hemisphere where it is a major pest of corn and can cause significant economic damage to a number of other crops. FAW has several traits that complicate efforts to mitigate infestations that include the capacity for long-distance flight, a large and diverse host range, and a demonstrated ability to evolve resistance to pesticides, including a subset of Bt proteins. In 2016, FAW was found to have become established in western Africa with infestations subsequently discovered in eastern Africa, the Indian subcontinent, southeastern Asia, and Australia by 2020. How and when FAW invaded the Old World remains an open question and is still an important one to assess the risk of future introductions of resistance phenotypes or strains with different host preferences that could complicate hemispheric control efforts. Here I present global comparisons of sequence variants in a Z-chromosome genetic marker (Tpi) that provide new insights into the possible Western Hemisphere source of the African FAW invasion and the approximate original entry point into the African continent.
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