The genus Fusarium is surely known by everyone who looks at moulds associated with plants and soil, especially with its characteristic hyaline, multiseptate, slightly curved macroconidia. Nevertheless, it still seems a daunting task identifying isolates to species. The complexity of the genus is reflected in the number of ascomycete genera such as Nectria, Calonectria and Gibberella, which have Fusarium as the anamorph state. On the other hand many species of Fusarium have no known teleomorph. Colin Booth, President of the BMS in 1977, produced an invaluable monograph on the genus (Booth, 1971) and later, reviews by Nelson et al. (1983) and Gerlach & Nirenberg (1982) also help to make the genus more accessible.