Hirsutella

Definition

A genus of anamorphic fungi (asexual morphs) in the family Ophiocordycipitaceae, characterized by slow-growing, often pale colonies with slender, tapering phialides that produce solitary, adhesive conidia. Species are obligate or facultative pathogens of insects, mites, and nematodes, penetrating hosts via adhesive conidia that germinate and form infection pegs. The teleomorphs (sexual stages) are classified in Ophiocordyceps. Several species, notably H. thompsonii and H. citriformis, have been investigated or commercialized as microbial biocontrol agents against mites and insects.

Etymology

From Latin hirsutus (hairy, bristly), referring to the hair-like or bristly appearance of the conidiophores.

Example

Hirsutella thompsonii, originally isolated from the citrus rust mite Phyllocoptruta oleivora, produces dense synnemata on infected mites and has been developed as a commercial mycoacaricide; H. citriformis infects lepidopteran larvae and is recognized by its distinctive citron-shaped conidia.

Related Terms

• Ophiocordyceps
• anamorph
• teleomorph
• entomopathogenic fungus
• Biological control
• mycoacaricide
• conidium
• phialide

Usage Notes

In formal taxonomic usage, Hirsutella refers specifically to the asexual morph; the corresponding sexual morph is placed in Ophiocordyceps following the one fungus, one name principle. The name has been applied to unrelated brachiopod and foraminiferan genera (homonyms), but in entomological and mycological contexts it refers exclusively to the fungal genus described by Patouillard. Identification to species requires microscopic examination of conidial shape and phialide morphology; H. thompsonii and H. rhossiliensis are among the most commonly encountered species in agricultural and ecological studies.