Seed Treatments to Overcome Soilborne Pathogen Pressure in Direct-Seeded Fiber Hemp

Hemp (Cannabis sativa L.) is grown for several uses including fiber, grain, and cannabinoids in both greenhouse and field settings. Low germination rates and poor stand establishment due to soilborne pathogens, particularly Pythium spp., can slow crop growth and limit yield under environmental conditions conducive to these pathogens. We tested the efficacy of biochemical seed treatments to prevent Pythium damping-off in a greenhouse experiment and found no significant differences in the percentage of healthy hemp cultivar ‘Vega’ seedlings when treated with copper hydroxide- and phosphite-based fungicides. Field experiments conducted in 2023 and 2024, utilizing ‘Futura 83’ and ‘Fibror 79’ cultivars of fiber hemp in small plot trials, were conducted to evaluate the ability of biochemical and chemical seed treatments to improve stand establishment and study their impact on yield, stem length, and stem diameter at harvest. Copper-based products performed best with significant differences in stand counts observed at early time points. Significant differences were not observed at harvest in stand count, fresh weight, stem length, or stem diameter. Future studies are needed to elucidate the relationship between seed treatments and natural stand thinning in fiber hemp, as well as the efficacy of these fungicide seed treatments on a broader selection of soilborne pathogens.