Exploring How Crop Pests Move Between North and South America

Jenn Hoskins
5th March, 2025

Exploring How Crop Pests Move Between North and South America

This figure demonstrates that COIB CSh haplotype frequencies of fall armyworm (Spodoptera frugiperda) show pronounced spatial and temporal heterogeneity among individual Mexican collections but relative stability in Texas, while pooled profiles from Mexico and Texas are similar, supporting the study’s conclusion that Mexico is characterized by localized, transient population structure rather than sustained mass migration.

Image adapted from: Nagoshi et al. / CC0 1.0 (Source)

Key Findings

  • A USDA study in Mexico found that fall armyworm populations rarely mix with those from North and South America
  • In Mexico, fall armyworms tend to stay in local areas instead of migrating long distances
  • This localized movement allows farmers to target specific regions for more effective pest control
The fall armyworm, Spodoptera frugiperda, is a significant threat to agriculture, particularly affecting corn and various other crops. Native to the Western Hemisphere, this pest has become a global concern since its arrival in Africa in 2016 and subsequent spread to Asia and Australia. One of the most challenging aspects of managing fall armyworm is its ability to migrate long distances, which facilitates the rapid spread of traits such as pesticide resistance, posing increased risks to agricultural productivity worldwide. A recent study conducted by the United States Department of Agriculture[1] investigates whether the Mexico-Central America land bridge serves as a pathway for gene flow between fall armyworm populations in North and South America. Understanding the movement patterns of fall armyworm is crucial for developing effective management strategies and mitigating the spread of harmful traits across continents. Previous research in Mexico suggested that geographical or meteorological barriers might limit the mass movement of fall armyworm populations[2]. Building on these findings, the current study analyzed genetic variation in fall armyworm collected from different regions in Mexico. By examining genetic patterns, the researchers aimed to determine whether there is significant gene flow between populations in North and South America through the Central America land bridge. The study employed several methods to achieve its objectives. Genetic analysis was conducted on fall armyworm samples to identify patterns of genetic diversity and structure. These genetic findings were then correlated with models of climate suitability, major corn production areas, and wind-dependent dispersal projections. Climate suitability models help predict regions where environmental conditions are favorable for fall armyworm persistence, while wind dispersion models estimate potential migration paths based on prevailing wind patterns. The results revealed a significant but transient genetic structure within Mexican fall armyworm populations. This structure aligns with the climate suitability and air transport projections, indicating that the movement of fall armyworm in Mexico is largely localized rather than involving long-distance migrations. Unlike the United States, where mass migratory populations are observed, the movement through Mexico does not support extensive gene flow between North and South American populations. This suggests that the Central America land bridge acts as a partial barrier, limiting the exchange and spread of fall armyworm across the two continents. These findings are consistent with earlier studies that highlighted the genetic variability within fall armyworm populations[2][3]. For instance, research has shown that most genetic variability in fall armyworm is found within populations rather than between them, indicating minor gene flow and suggesting that populations are largely interbreeding within localized areas[2]. Additionally, population genomics studies have identified a panmictic population structure with minor reductions in gene flow between overwintering populations[4]. The current study builds on this knowledge by demonstrating that geographical and climatic factors in Mexico further restrict large-scale gene flow between American populations. Understanding the limited gene flow through Mexico has important implications for managing fall armyworm populations. It suggests that interventions can be more localized, focusing on specific regions rather than assuming widespread migration. This localized dispersal behavior can help in designing targeted pest management strategies, potentially reducing the spread of pesticide resistance and other harmful traits[5]. Moreover, the study's integration of genetic data with climate and wind dispersion models provides a comprehensive approach to predicting fall armyworm movement. By identifying areas with optimal climate conditions for fall armyworm persistence, such as eastern and central Africa[5], and understanding how these areas can act as hotspots for migration, researchers can better anticipate and respond to potential infestations. This approach ensures that pest management efforts are informed by a combination of genetic insights and environmental factors, enhancing their effectiveness. The findings also highlight the importance of continuous monitoring and genetic analysis of fall armyworm populations. As fall armyworm continues to spread to new regions, understanding the genetic structure and movement patterns will be essential for predicting future invasions and mitigating their impact on agriculture. The study underscores the need for international collaboration and data sharing to track and manage the global spread of this pest effectively. In conclusion, the research by the United States Department of Agriculture provides valuable insights into the movement and genetic structure of fall armyworm populations in Mexico. By demonstrating that the Mexico-Central America land bridge does not facilitate extensive gene flow between North and South American populations, the study highlights the importance of localized pest management strategies. These findings, combined with previous research on genetic variability and population genomics, offer a robust framework for understanding and combating the global threat posed by fall armyworm.

AgricultureEcologyAnimal Science

References

Main Study

1) Assessing the potential for fall armyworm exchanges between the two American continents across the Mexico-Central America land bridge

Published 3rd March, 2025

https://doi.org/10.1371/journal.pone.0308501

Related Studies

2) Population variation of the fall armyworm, Spodoptera frugiperda, in the Western Hemisphere.

https://doi.org/10.1673/031.007.0501

3) Modeling seasonal migration of fall armyworm moths.

https://doi.org/10.1007/s00484-015-1022-x

4) Whole genome comparisons reveal panmixia among fall armyworm (Spodoptera frugiperda) from diverse locations.

https://doi.org/10.1186/s12864-021-07492-7

5) Potential distribution of fall armyworm in Africa and beyond, considering climate change and irrigation patterns.

https://doi.org/10.1038/s41598-021-04369-3


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