The fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera, Noctuidae), is a well-known agricultural pest in its native range, North and South America, and has become a major invasive pest around the globe in the past decade. In this review, we provide an overview to update what is known about S. frugiperda in its native geographic ranges. This is followed by discussion of studies from the invaded areas to gain insights into S. frugiperda's ecology, specifically its reproductive biology, host plant use, status of insecticide resistance alleles, and biocontrol methods in native and invasive regions. We show that reference to host strains is uninformative in the invasive populations because multidirectional introduction events likely underpinned its recent rapid spread. Given that recent genomic analyses show that FAW is much more diverse than was previously assumed, and natural selection forces likely differ geographically, region-specific approaches will be needed to control this global pest.

The recent discovery of fall armyworm (Spodoptera frugiperda, J.E. Smith) in Africa presents a significant threat to that continent’s food security. The species exhibits several traits in the Western Hemisphere that if transferred to Africa would significantly complicate control efforts. These include a broad host range, long-distance migratory behavior, and resistance to multiple pesticides that varies by regional population. Therefore, determining which fall armyworm subpopulations are present in Africa could have important implications for risk assessments and mitigation efforts. The current study is an extension of earlier surveys that together combine the collections from 11 nations to produce the first genetic description of fall armyworm populations spanning the sub-Saharan region. Comparisons of haplotype frequencies indicate significant differences between geographically distant populations. The haplotype profile from all locations continue to identify Florida and the Caribbean regions as the most likely Western Hemisphere origins of the African infestations. The current data confirm the uncertainty of fall armyworm strain identification in Africa by genetic methods, with the possibility discussed that the African infestation may represent a novel interstrain hybrid population of potentially uncertain behavioral characteristics.

A critical component for sustaining adequate food production is the protection of local agriculture from invasive pest insects. Essential to this goal is the ability to accurately distinguish foreign from closely related domestic species, a process that has traditionally required identification using diagnostic morphological "keys" that can be both subtle and labor-intensive. This is the case for the Lepidopteran group of insects represented by Spodoptera, a genus of Noctuidae "armyworm" moths that includes several important agricultural pests. Two of the most destructive species, Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) and S. litura (F.) are not yet established in North America. To facilitate the monitoring for these pests, the feasibility of using DNA barcoding methodology for distinguishing between domestic and foreign Spodoptera species was tested. A DNA barcoding database was derived for a subset of Spodoptera species native to Florida, with an emphasis on those attracted to pheromone blends developed for S. litura or S. littoralis. These were then compared to the barcode sequences of S. litura collected from Taiwan and S. littoralis from Portugal. Consistent discrimination of the different species was obtained with phenetic relationships produced that were generally in agreement with phylogenetic studies using morphological characteristics. The data presented here indicate that DNA barcoding has the potential to be an efficient and accurate supplement to morphological methods for the identification of invasive Spodoptera pests in North America.

The fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is an invasive insect pest attacking maize in Ghana and sub-Saharan Africa countries. Biological control will need to be an important management strategy, and a first step was to identify potential natural enemies. Sampling was conducted in different localities of the 10 regions of Ghana from May to Nov 2017. A total of 1,062 larvae were collected from 106 maize farms, and the presence of natural enemies was recorded in 18 (17.0%) farms. Among natural enemies recorded, 7 species were parasitoids: Chelonus bifoveolatus Szpligeti, Coccygidium luteum (Brull), Cotesia icipe Fernandez, Meteoridea testacea (Granger), and Bracon sp. (all Hymenoptera: Braconidae), Anatrichus erinaceus Loew (Diptera: Chloropidae), and an undetermined tachinid fly (Diptera: Tachinidae). The parasitism rate was 3.58%. Three predator species were collected: Pheidole megacephala (F.) (Hymenoptera: Formicidae), Haematochares obscuripennis Stål, and Peprius nodulipes (Signoret) (both Heteroptera: Reduviidae). The 2 most abundant parasitoids were C. bifoveolatus and C. luteum with a relative abundance of 29.0% and 23.7%, respectively, and a parasitism rate of 1.04% and 0.85%, respectively. However, C. bifoveolatus was the most dispersed parasitoid, found in 6.6% of the inspected sites within all the agroecological zones of Ghana. This species is a good candidate as a biological control agent for fall armyworm in Africa. The predator that was most abundant (46.0%) and dispersed (3.8% of the farms) was P. megacephala.

The invasion of the Western Hemisphere native fall armyworm (Spodoptera frugiperda; J. E. Smith) (Lepidoptera: Noctuidae) into the Eastern Hemisphere has been notable for the rapidity and geographical breadth of new detections. In the year following the first discovery in western sub-Saharan Africa in 2016, infestations have been documented in most sub-Saharan maize growing regions and has now expanded beyond Africa with populations recently reported in India. These observations could indicate a remarkable capacity for rapid establishment and long-distance dissemination. However, while fall armyworm does exhibit extended migration in North America where it annually traverses thousands of kilometers, this behavior is known to be dependent on highly favorable wind patterns and so can’t be assumed to occur in all locations. An alternative possibility is that the species has long been present in Africa, and perhaps the rest of the hemisphere, but was undetected until the enhanced monitoring that resulted after its initial discovery. Determining whether the fall armyworm in the Eastern Hemisphere is newly arrived or long pre-existing is important for assessing the risks of significant economic impacts, as the former indicates a change in pest composition while the latter does not. This study examined this issue by comparing collections from two geographically distant locations, South Africa and India. Sequence comparisons were used to quantify differences between the South Africa and India collections, assess the likelihood of their sharing a common source population, and their possible relationship with previously characterized fall armyworm from other regions of Africa. The results indicate genetic homogeneity between the South African and Indian fall armyworm populations tested and substantial similarities between these and collections from eastern Africa. The implications of these findings on fall armyworm population behavior and composition are discussed.

The fall armyworm Spodoptera frugiperda (J. E. Smith) invaded several West African countries in 2016 causing severe injury to maize plants and economic damage. This study assesses variations in the occurrence of this species in different Agro-Ecological Zones (AEZs) in Togo and Ghana during the 3 yr following its discovery. The surveys were conducted on 120 farms in Togo and 94 farms in Ghana by collecting larvae from 200 maize plants per hectare. Infestation levels were 68.46% in 2016, 55.82% in 2017, and 17.76% in 2018. The number of larvae recorded per hectare and infestation levels were higher in Togo than in Ghana. The lowest number of collected larvae and infestation levels of S. frugiperda were in 2018, compared to the other 2 yr. Larvae per hectare and the infestation level varied regionally inside the two countries. The southern part of Togo (AEZ five) contained higher numbers of larvae and higher infestation levels during the 2 yr following the invasion of the pest. We concluded that infestation levels of S. frugiperda are much lower in 2018 than the two previous years and it is therefore necessary to determine the factors that affect the population dynamics of S. frugiperda in the field, which is a perquisite for developing management interventions.