Mulching and Time of Planting Impact on Southern Blight Disease and Industrial Hemp Production

Southern blight, a disease caused by the soil-borne fungus Sclerotium rolfsii (S. rolfsii), is favored by the hot and humid conditions of the southeastern United States, posing a significant challenge to hemp production in Tennessee. Black plastic mulch (BPM), commonly used for weed control, can exacerbate the disease. There is limited information on the effects of straw mulch (SM), known to moderate soil temperatures and moisture, or planting time in disease management. Field studies were conducted in 2022 and 2023 at Tennessee State University to evaluate the effects of planting time, mulch type, and biofungicide application on disease severity, weed suppression, plant growth, and cannabinoid production in floral hemp. SM significantly reduced southern blight severity and moderated soil temperature, while BPM increased both. Early planting reduced disease severity by 28% in 2022 and by 53% and 34% in 2023 for first and second planting dates. SM lowered soil temperature by 6%, enhanced chlorophyll content by 30%, and increased plant height and biomass by 20% and 25%, respectively. Early planting increased cannabidiol (CBD) concentration by 0.4%, while late planting increased tetrahydrocannabinol (THC) by 0.25%. These findings demonstrate that integrating straw mulch with early planting can reduce disease severity, stabilize soil microclimate, and enhance hemp productivity under warm, humid conditions.