f.sp. cannabis and F. oxysporum f.sp. vasinfectum, was first noted in eastern Europe (Russia, the Czech Republic, Poland, and Romania) more than 50 years ago; it also reportedly occurs in western Europe (Italy and France), central Asia (Kazakhstan and Pakistan), and North America (Canada and the United States) (McPartland and Hillig 2004).
F. oxysporum f.sp. cannabis and F. oxysporum f.sp. vasinfectum are morphologically similar in culture, but, according to McPartland and Hillig (2004), the two can be differentiated on the basis of their host range. F. oxysporum f.sp. cannabis is reported to infect only cannabis, whereas the host range of F. oxysporum f.sp. vasinfectum includes (in addition to cannabis) cotton, mungbean, pigeon pea, rubber tree, alfalfa, soybean, coffee, tobacco, and other plants (McPartland and Hillig 2004). The study of genetic variability with DNA polymorphisms may provide an alternative route for identification of these two formae speciales.
F. oxysporum f.sp. cannabis was considered a potential control agent for cannabis as early as the 1970s on the basis of its purported specificity to members of the genus Cannabis, its ability to survive in the soil for extended periods, and the likelihood of infecting new plantings of the crop. Hildebrand and McCain (1978) conducted laboratory experiments to develop a suitable technique for the production of F. oxysporum f.sp. cannabis inoculum consisting of chlamydospores, which are suitable for soil application. Later, McCain and Noviello (1985) explored the feasibility of using F. oxysporum f.sp. cannabis (isolated in Italy) as a biological control agent against C. sativa and claimed that the fungus caused disease only on C. sativa and that it was able to survive in the soil for at least one growing season.
In the late 1990s, Tiourebaev et al. (2001) conducted experiments to test the pathogenicity of F. oxysporum f.sp. cannabis isolates obtained from diseased cannabis plants collected in various regions of Kazakhstan and to determine their virulence, their host range, and the formulation best suited for field application. The findings led them to conclude that the disease caused by F. oxysporum f.sp. cannabis was not severe enough to cause “permanent and lasting control” of cannabis plants and that there was a need for an improved formulation and improved delivery systems to enhance the pathogen’s efficacy as a mycoherbicide (Tiourebaev et al. 2001). The results of those studies are reviewed below in the context of efficacy,