Biological Control of Infestations of Ditchweed (Cannabis sativa) with Fusarium oxysporum f.sp. Cannabis in Kazakhstan

Ditchweed (Cannabis sativa L.) is widely distributed in the Chu Valley of southeast Kazakhstan and is difficult to control using conventional chemical or mechanical control. Thus, plant pathogens were investigated as potential biocontrol agents. Fusarium oxysporum was isolated from symptomatic C. sativa plants from this area. Twenty-five of the isolated strains of F. oxysporum were pathogenic and host-specific to C. sativa in greenhouse studies. These strains of F. oxysporum f. sp. cannabis were further evaluated as mycoherbicides for control of ditchweed in natural field infestations. Twelve strains showed field control of C. sativa, and the most virulent strain elicited wilt symptoms within 2 weeks of inoculation of field plants. Three different mycoherbicide formulations were evaluated. A birch sawdust formulation was the most effective carrier in the field. Food based formulations were heavily predated by birds, rodents and insects.