Septoria epambrosiae sp nov on Ambrosia artemisiifolia (common ragweed)

Recently an unidentified Septoria was reported to be pathogenic on Ambrosia artemisiifolia L. (common ragweed) in Hungary and may have potential as a biocontrol agent for this noxious weed. After reviewing the two previously known species of Septoria on Ambrosia (Asteraceae), the Septoria from Hungary is described as a new species, Septoria epambrosiae. A synopsis of the three species of Septoria on Ambrosia is provided. Based on a molecular analyses of the nSSU and complete ITS region of the rDNA, the taxonomic relationships of S. epambrosiae are determined. Septoria epambrosiae clusters with members of the Dothideales with the teleomorph most likely a species of Mycosphaerella.