Efficacy of chemical and biological spray seed treatments in preventing garlic dry rot

Garlic dry rot caused by Fusarium proliferatum is an emerging postharvest disease that has resulted in severe economic losses, necessitating design and implementation of efficient disease control strategies. Sanitation of planting cloves is critical for preventing garlic dry rot. This study evaluated the efficacy of commercial chemicals and biocontrol agents, applied at planting as spray treatments, for reducing disease severity and the occurrence of Fusarium spp. in garlic, from the field stage then through 9 months of postharvest storage. Tebuconazole was the most effective for reducing disease severity, giving 26.5% reduction of basal plate rots and 44% reduction of bulb rots, and 33.4% reduction in visible symptoms on cloves relative to the untreated controls. Comparable results were obtained by applying B. subtilis and S. griseoviridis. However, none of the active ingredients tested in this study reduced the incidence of F. oxysporum and F. proliferatum on basal plates, although tebuconazole reduced the postharvest incidence of F. proliferatum on cloves by nearly 50%. Incidence of F. proliferatum increased by 37% in bulbs transferred from storage to room temperature (25°C) for 15 days, simulating storage in consumers’ homes. These results demonstrate that spray seed clove treatments have inhibitory effects on postharvest garlic dry rot, although further research is required to determine the persistence of these treatments during prolonged storage, especially without low temperatures.