New species () from the USA and Taiwan associated with ambrosia beetles and plant hosts.

() is a genus of more than 20 ophiostomatoid fungi commonly occurring in symbioses with wood-boring ambrosia beetles. We examined ambrosia beetles and plant hosts in the USA and Taiwan for the presence of these mycosymbionts and found 22 isolates representing known and undescribed lineages in . From 28S rDNA and β-tubulin sequences, we generated a molecular phylogeny of and observed morphological features of seven cultures representing undescribed lineages in . From these analyses, we describe five new species in .: , , , , and spp. nov. Our analyses also identified two plant-pathogenic species of associated with previously undocumented beetle hosts: (1) , the causative agent of Japanese oak wilt, from and in Taiwan, and (2) , the pathogen responsible for laurel wilt, from in Florida. The results of this study show that and associated ophiostomatoid fungi have been poorly sampled and that future investigations on ambrosia beetle mycosymbionts should reveal a substantially increased diversity.