Using genetic comparisons of populations from Arizona, Mexico, and Texas to investigate fall armyworm migration in the American southwest

Authors: Nagoshi, Rodney; TESSNOW, ASHLEY - Texas A&M University; CARRIERE, YVES - University Of Arizona; BRADSHAW, JEFF - University Of Nebraska; HARRINGTON, KYLE - University Of Arizona; SWORD, GREGORY - Texas A&M University; Meagher, Robert - Rob

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/13/2023
Publication Date: 11/17/2024
Citation: Nagoshi, R.N., Tessnow, A.E., Carriere, Y., Bradshaw, J., Harrington, K., Sword, G.A., Meagher Jr, R.L. 2024. Using genetic comparisons of populations from Arizona, Mexico, and Texas to investigate fall armyworm migration in the American southwest. PLOS ONE. 18(11). Article e0289060. https://doi.org/10.1371/journal.pone.0289060.
DOI: https://doi.org/10.1371/journal.pone.0289060

Interpretive Summary: Fall armyworm is a significant agricultural pest native to the Western Hemisphere that has become a global problem with its discovery in most of the Eastern Hemisphere. It causes substantial economic losses in corn and can be a significant problem in many other crops. The inability of fall armyworms to survive freezing winters limits permanent populations to areas south of 30°N latitude, with known overwintering locations that include southern Florida, southern Texas, and portions of Mexico. Fall armyworm infestations are routinely found in agricultural areas as far west as southern Arizona. Climate suitability analyses indicate that these western infestations most likely arise from annual migrations whose source(s) have yet to be identified. In this study, scientists from USDA-ARS, Center for Medical, Agricultural and Veterinary Entomology in Gainesville FL, in collaboration with scientists from other ARS locations and three universities used genetic techniques to identify possible migratory pathways in the American southwest. The results show genetic similarities between the fall armyworms from Arizona with those from Texas and Sinaloa, Mexico consistent with migration, while also indicating significant barriers to migration within Mexico. The results are a significant contribution to identifying the source of infestations in the American southwest by this important agricultural pest and provide greater insights into barriers for effective pest management strategies.

Technical Abstract: Fall armyworm (FAW) is a significant agricultural pest native to the Western Hemisphere that has become a global problem with its discovery in most of the Eastern Hemisphere. It causes substantial economic losses in corn and can be a significant problem in many other crops. Complicating efforts to control this pest is its ability for long distance flights. These have best been characterized in the central and eastern sections of the United States where it dramatically expands its range annually from the Mexico border to Canada during the growing season. The inability of FAW to survive freezing winters limits permanent populations to areas south of 30°N latitude, with known overwintering locations that include southern Florida, southern Texas, and portions of Mexico. FAW infestations are routinely found in agricultural areas as far west as southern Arizona and California, though these have not been genetically characterized. Climate suitability analyses indicate that neither state can consistently support permanent FAW populations, indicating that these western infestations most likely arise from annual migrations whose source(s) have yet to be identified. In this study the FAW from Arizona and representative specimens from a selection of permanent and migratory FAW populations were genetically characterized with mitochondrial and Z-linked markers frequently used in FAW field studies. Comparisons were made to describe the relationships between these populations and identify possible migratory pathways in the American southwest. The results show genetic similarities between the FAW from Arizona with those from Texas and Sinaloa, Mexico consistent with significant interactions between these populations suggestive of migratory interactions. The data also suggest significant barriers to migration within Mexico. Evidence was found that two genetically-distinct FAW subpopulations known as “host strains” have a differential distribution in the southwest that may indicate significant differences in migration behavior.