Clavicipitales: Beauveria

Beauveria Vuill.

Vegetative growth white or pale, with hyaline trailing hyphae or forming simple loose masses on the host, with whorls or dense clusters of conidiogenous cells forming balls of dry and powdery conidia.

Conidia produced singly and separately, from short globose or flask-shaped conidiogenous cells which have an apical denticulate rhachis with a distinctly zig-zag appearance. Conidia one-celled, hyaline, thin-walled, smooth, globose to ellipsoidal, sometimes with an apiculate base.

Beauveria species are ubiquitous and well-known as insect pathogens, but have been recorded from other sources, mostly of animal origin. They can also be isolated from the soil in which their hosts overwinter. No teleomorphs are known.

There is much early literature on the genus, but more recently it has been discussed by de Hoog (1972) and Samson & Evans (1982). The most up-to-date taxonomic treatment is by Mugnai et al. (1989), who recognized seven species, almost all from diseased arthropods. Brady (1979) has provided descriptions of two of the most important species. Their industrial interest lies in the field of biological control.

Beauveria bassiana (Bals.) Vuill. is the best-known species. It has closely clustered conidiogenous cells and globose to broadly ellipsoidal, occasionally apiculate conidia 2-3 x 2-2.5µm in size. B. bassiana was first recorded as the “white muscardine” disease of silk worms.

Beauveria brongniartii (Sacc.) Fetch is less common, is also referred to as “white muscardine” and is also used in biological control. It often has slightly less closely clustered conidiogenous cells, and conidia (2-) 2.5-4 (-6)µm in length which are always cylindrical or ellipsoidal rather than globose.