The soybean stem fly, Melanagromyza sojae, an Asian native insect, has successfully established in Brazil, Argentina, Paraguay and Bolivia. These countries are among the lead global soybean producing nations, being collectively known as the soybean belt of South America. Infestation levels of M. sojae grow by the year, facilitated by the lack of efficient management strategies. Previous studies have revealed a high number of maternal lineages in M. sojae populations from Southern Brazil and Paraguay, but a comprehensive survey on genetic diversity combining samples from all countries within the South American soybean belt remains absent. We used the mitochondrial DNA cytochrome oxidase I partial gene (mtCOI) to characterize specimens of M. sojae collected in fourteen Brazilian sites and one Argentine site, and then combined our mtCOI data with previously published data from Australia, Bolivia, Paraguay, and other Brazilian sites, to investigate genetic diversity in this invasive agricultural pest species. Based on the molecular characterisation of the mtCOI gene, haplotypes Msoj-COI-01 and Msoj-COI-02 have the highest frequencies in the continent. The

This is the first scientific record of Melanagromyza sojae in Bolivia, confirmed through molecular characterization of the mtDNA COI gene. Commonly known as the soybean stem fly, M. sojae belongs to the family Agromyzidae and is a highly polyphagous pest, attacking several plant species of the Fabaceae family, such as soybeans and other beans. Previously reported in Brazil and Paraguay, the soybean stem fly presence was confirmed in soybean fields of the municipalities of Fernández Alonso, Cuatro Cañadas, Santa Cruz de la Sierra, Yapacani and Santa Rosa del Sara, which are located in Santa Cruz Department, Bolivia. This soybean stem fly detection in Bolivia will affect soybean crop practices in South America.