| Geosmithia | |
|---|---|
 | |
| Geosmithia morbida on leaves of black walnut | |
Scientific classification  | |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Sordariomycetes |
| Order: | Hypocreales |
| Family: | Bionectriaceae |
| Genus: | Geosmithia Pitt (1979) |
| Type species | |
| Geosmithia lavendula (Raper & Fennell) Pitt (1979) | |
Geosmithia is a genus of anamorphic fungi of uncertain familial placement in the order Hypocreales. The genus, circumscribed by Australian mycologist John Pitt in 1979, [1] is widely distributed. A 2008 estimate placed ten species in the genus, [2] but several new species have since been described. Thousand cankers disease, which affects economically important black walnut (Juglans nigra) populations in North America, is caused by Geosmithia morbida . [3]
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Species in the genus are generally similar to those in Penicillium , but can be distinguished from them by forming cylindrical conidia from rough-walled phialides. Additionally, the conidia of Geosmithia do not have a green color, in contrast to the characteristic blue-grey or green-grey conidia of Penicillium. Some Geosmithia species have teleomorphic forms that are classified in the genus Talaromyces . However, Geosmithia is a polyphyletic taxon with evolutionary affinities to at least three groups of the euascomycete lineage within the Ascomycota. [4] The generic name Geosmithia honors British mycologist George Smith. [1]
