Several species in the Euwallacea fornicatus complex have emerged as important pests of woody plants globally, particularly in habitats where they are invasive aliens. These beetles live in obligate symbioses with fungi in the genus Fusarium. In this study, we identified Euwallacea spp. and their fungal mutualists that have emerged as pests of planted Acacia crassicarpa in Riau, Indonesia. Morphological identification and phylogenetic analyses of the mitochondrial cytochrome oxidase c subunit I (COI) gene confirmed that E. similis and E. perbrevis are the most abundant beetles infesting these trees. Multilocus phylogenetic analyses of their fungal mutualists revealed their nonspecific association with six Fusarium species. These included F. rekanum and five novel Fusarium mutualists within the Fusarium solani species complex (FSSC), four of which reside in the Ambrosia Fusarium Clade (AFC). These new species are described here as F. akasia, F. awan, F. mekan, F. variasi, and F. warna.
Keywords: 5 new taxa; Ambrosia Fusarium Clade (AFC); Ambrosia beetles; Euwallacea symbiosis; Fusarium.