A reevaluation of the host range and geographical distribution of Claviceps species in the United States

A listing of host and state reports and distribution maps for 11 taxa of Claviceps occurring in the United States, including C. africana, C. cinerea, C. grohii, C nigricans, C. paspali, C pusilla, C. purpurea var. purpurea and var. spartinae, C tripsaci, C yanagawensis, and C zizaniae, was prepared based on literature citations and examination of specimens from herbaria. The occurrence of C ranunculoides is questioned based on examination of conidia and sclerotia from archived specimens. Collections of C purpurea var. purpurea from grasses in the Panicoideae were referred to other Claviceps spp. based on occurrence of macroconidia and microconidia. C purpurea var. purpurea was found on 165 grass species within the continental United States and Alaska. The size of conidia of C purpurea var. purpurea was found to be relatively stable across host and geographical regions. However, conidia of C purpurea var. purpurea from hosts in the Aveneae and Meliceae (generally associated with wet habitats) were more variable in size and generally larger than those from other tribes in the Pooideae. Claviceps spp. in the continental United States occurred in diverse habitats, including temperate grasslands of the middle to northern latitudes (C purpurea var. purpurea, C nigricans) to the middle to southern latitudes (C pusilla), coastal habitats (C purpurea var. spartinae, C zizaniae), northern wetlands (C grohii), southern temperate to subtropical grasslands (C africana, C paspali, C. tripsaci, C. yanagawensis), and and southwestern grasslands (C cinerea).