Oregano (Origanum vulgare) cultivation is of great economic importance in Peru. Tacna stands out as its main producer. However, the presence of phytopathogenic fungi represents a challenge for its production. This study aimed to characterize both the morphological and molecular levels of the causal agent of crown and root rot in a crop field in the Camilaca district, Candarave, Tacna. To this end, systematic sampling was carried out using the five-gold method, collecting plants with typical symptoms. Fungi were isolated from diseased roots and characterized using macroscopic and microscopic morphological analysis as well as sequencing and multilocus phylogenetic analysis (ITS, 28S, HIS3, TEF1, TUB2). In addition, pathogenicity tests were performed on healthy plants to confirm the infectivity of the isolates. The results demonstrated that root rot was caused by a complex of phytopathogenic fungi through phylogenetic analysis of Dactylonectria torresensis, Fusarium oxysporum, F. iranicum, and F. redolens. These findings represent the first report of these species as causal agents of oregano root rot in Peru, highlighting the need for integrated management strategies that reduce the economic impact of these diseases and contribute to the sustainability of the crop in key producing regions such as Tacna.

High-Andean drylands are environmentally heterogeneous ecosystems, yet soil bacterial communities in southern Peru remain poorly characterized. This exploratory study examined bacterial communities in 23 soil samples collected from five sites in Candarave, Tacna, representing herbaceous–shrubland, succulent shrubland, and agricultural environments that also differed in elevation, soil pH, moisture, and historical aridity descriptors. Bacterial communities were characterized by 16S rRNA gene amplicon sequencing. Actinobacteriota, Chloroflexota, and Proteobacteria predominated across the sampled sites. Alpha diversity differed among sites (Kruskal–Wallis, p ≤ 0.009) and was highest at the two agricultural sites (P4 and P5; Shannon index, 11.33 ± 0.34 and 11.35 ± 0.17) and lowest at the herbaceous–shrubland site P1 (9.52 ± 0.75). ANCOM-BC indicated higher abundances of Azospirillales at both agricultural sites and of Blastococcus and Solirubrobacter mainly at P4, whereas Candidatus Udaeobacter and Conexibacter were more strongly represented at P3, the succulent shrubland site. Unweighted UniFrac analysis showed marked differences in bacterial community composition among the five sampling sites (PERMANOVA, pseudo-F = 4.67, p = 0.001), while multivariate dispersion did not differ significantly (PERMDISP, F = 0.686, p = 0.153). These results provide a descriptive baseline for soil bacterial diversity in an understudied high-Andean region and document substantial community heterogeneity among sites differing simultaneously in environmental conditions, vegetation, and land use.