Demonstration Using Field Collections that Argentina Fall Armyworm Populations Exhibit Strain-specific Host Plant Preferences

Abstract

Spodoptera frugiperda, the fall armyworm, is a major economic pest throughout the Western Hemisphere of corn (maize), cotton, sorghum, and a variety of agricultural grasses and vegetable crops. Studies in the United States, the Caribbean, and Brazil demonstrated the existence of two subpopulations (previously designated "host strains") that differ in their choice of plant host. Specifically, the corn strain is preferentially found in corn and sorghum, while the rice strain is dominant in rice, turf grass, and alfalfa. However, inconsistent results were reported in surveys of fall armyworm in Argentina, with some indicating that the host plant preferences of the two strains might be compromised or even nonexistent. If correct, this would complicate efforts to control this pest by considerably expanding the range of habitats that would have to be considered as potential sources for fall armyworm infestations in specific crops. A reexamination of Argentine fall armyworm, this time with field collections rather than the laboratory colonies used in previous studies, confirmed the existence of the two strains and their host preferences. Specifically, the corn strain was consistently the majority population infesting corn and was usually so in sorghum, while the rice strain was predominant in pasture/turf grasses and alfalfa. The one outlier was a collection from rice, which had a corn strain majority. Overall, the data were generally consistent with strain behaviors observed in other areas of the Western Hemisphere.

Comparative molecular analyses of invasive fall armyworm in Togo reveal strong similarities to populations from the eastern United States and the Greater Antilles

“…The proportions of the two strains differed depending on the marker used, with Tpi giving a substantially higher corn-strain percentage than CO1 (Fig 4). These results indicate that the Togo fall armyworm is displaying a marker pattern consistently found in the Western Hemisphere, namely that the Tpi strain-biased polymorphisms consistently showed a stronger correlation with plant hosts than the CO1 haplotypes [21, 23, 26]. Overall, the data are consistent in indicating that while the rice-strain appears to be present in Africa, it is a minor component of the fall armyworm populating infesting corn in Togo.…”

“…These observations illustrate that the strain-specific associations observed with existing markers are not absolute. Discordances between host plant to molecular markers and between different markers have been observed in multiple locations and can be substantial [11, 22, 25, 26]. The reasons for this variability is unknown, but contributing factors could include incomplete fixation of the markers to the two strains, variability in strain behaviors, or hybridization between strains.…”

Developmental Parameters of Spodoptera frugiperda (Lepidoptera: Noctuidae) Immature Stages Under Controlled and Standardized Conditions

“…However, even when exposed to similar temperature conditions, there are reports of significantly longer larval development periods when S. frugiperda are fed less adequate artificial diet (Clavijo et al, 1991;Murúa et al, 2003), less suitable host plants (e.g., Marques, 1932;Leiderman & Sauer, 1953;Pencoe & Marti, 1981Nieto-Hernández & Llanderal-Cázares, 1982;Pitre & Hogg, 1983;Silveira et al, 1997;Botton et al, 1998;Lopes et al, 2008;Campos et al, 2011), or obtained from different collection locations (Giolo et al, 2002, Busato et al, 2005, 2008Boregas et al, 2013). Under similar conditions of suitable food and temperature, such variations are related to genetic variation from different geographic locations or biotypes related to the host plant (e.g., Giolo et al, 2002;Busato et al, 2005;Vélez-Arango, Arango, Villanueva, Aguilera, & Saldamando, 2008;Murúa et al, 2008, Murúa, Juárez, Prieto, & Willink, 2009, Murúa et al, 2015Salinas-Hernandez & Saldamando-Benjumea, 2011;Nagoshi et al, 2017).…”

“…Among Spodoptera species, at least fifteen are considered key pests of cultivated plants (Tood & Poole, 1980;Pogue, 2002;Angulo, Olivares, & Weigert, 2008). The fall armyworm, Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae), is recognized as one of the most important noctuid moth pests of North and South America (e.g., Chittenden, 1901;Luginbill, 1928;Vickery, 1929;Ashley, Wiseman, Davis, & Andrews, 1989;Pogue, 2002;Casmuz et al, 2010;Murúa et al, 2015). Recently, S. frugiperda has also been detected causing damage in the African continent (Goergen, Kumar, Sankung, Togola, & Tamò, 2016), in India (Sharanabasappa et al, 2018), and there have been interception reports in Europe, with specimens detected in Germany and The Netherlands (CABI, 2017).…”

Host Plants ofSpodoptera frugiperda(Lepidoptera: Noctuidae) in the Americas

“…The fall armyworm, Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae), is recognised as one of the most important noctuid moth pests of North and South America (Chittenden 1901;Luginbill 1928;Vickery 1929;Ashley et al 1989;Pogue 2002;Casmuz et al 2010;Murúa et al 2015). In addition, this pest has recently spread to Africa (Goergen et al 2016) and has been intercepted in Europe, with specimens collected in Germany and the Netherlands (CABI 2017).…”