<Emphasis Type="Italic">Helicocollum</Emphasis>, a new clavicipitalean genus pathogenic to scale insects (Hemiptera) in Thailand

A new genus pathogenic to scale insects (Coccidae, Hemiptera), Helicocollum, is described from Thailand. It includes the three species, H. chanthaburiensis, H. krabiensis and H. surathaniensis. Phylogenetic inferences on the basis of partial sequences of the large subunit of the nuclear ribosomal DNA, translation elongation factor 1-α and RNA polymerase II subunit 1 place the new genus in the Clavicipitaceae, although morphological features of the phialides resemble Hirsutella in the Ophiocordycipitaceae. Within the Clavicipitaceae, Helicocollum is closely related to Aschersonia, Moelleriella, Regiocrella, and Samuelsia, all known as pathogens of scale insects. Helicocollum differs from other scale insect pathogens in having phialides with helical necks and synnematous or sporodochial conidiomata, but pycnidia. Morphological characteristics are evaluated and compared with other asexual morphs producing twisted, undulated phialidic necks or occurring on scale insects.