Bidens pilosa and B. subalternans are highly noxious herbaceous neotropical asteraceous weeds. A survey of fungal pathogens associated with these two species was undertaken in Brazil, aimed at finding natural enemies in order to establish the potential for introducing novel specific pathogens from other regions of the world, as classical biological control agents. Ten fungal species were found associated with both B. pilosa and B. subalternans, namely: Cercospora bidentis, C. maculicola, Entyloma bidentis, E. compositarum, E. guaraniticum, Neoerysiphe cumminsiana, Plasmopara halstedii, Podosphaera xanthii, Uromyces bidentis, and U. bidenticola. Three other species were found solely associated only with B. subalternans: Colletotrichum bidentis, Pseudocercosporella bidentis and Sphaceloma bidentis. Pseudocercosporella bidentis is described herein as new to science.