In recent years perennial grasses such as the native tallgrass prairie plant Panicum virgatum
(switchgrass) have taken on a new role in the North American landscape as a plant-based
source of renewable energy. Because switchgrass is a native plant, it has been suggested
that disease problems will be minimal, but little research in this area has been conducted.
Recently, outbreaks of switchgrass anthracnose disease have been reported from the
northeastern United States. Incidences of switchgrass anthracnose are known in North
America since 1886 through herbarium specimens and disease reports, but the causal
agent of this disease has never been experimentally determined or taxonomically evaluated.
In the present work, we evaluate the causal agent of switchgrass anthracnose,
a new species we describe as Colletotrichum navitas (navitas ¼ Latin for energy). Multilocus
molecular phylogenetics and morphological characters show C. navitas is a novel species
in the falcate-spored graminicolous group of the genus Colletotrichum; it is most closely related
to the corn anthracnose pathogen Colletotrichum graminicola. We present a formal description
and illustrations for C. navitas and provide experimental confirmation that this
organism is responsible for switchgrass anthracnose disease.