Postharvest Management of Neoscytalidium dimidiatum Using GRAS Potassium Salts

Abstract

Neoscytalidium dimidiatum is an emerging fungal pathogen of increasing phytosanitary concern due to its wide host range, aggressive postharvest behavior, and expanding geographical distribution, yet comprehensive evaluations of safe, effective control measures such as potassium salts remain limited. This study investigated eight potassium salts-acetate, benzoate, bicarbonate, carbonate, citrate, metabisulfite, phosphate, and sorbate-compared to three commercial fungicides (imazalil, thiophanate-M, and tebuconazole + fluopyram) for their antifungal efficacy against N. dimidiatum in vitro (culture assays) and in vivo (postharvest apple fruit trials). In vitro assessments revealed potassium metabisulfite (EC50 = 4.4 x 10-5 g mL-1) and potassium sorbate (EC50 = 9.0 x 10-5 g mL-1) as the most effective salts, demonstrating antifungal activity comparable to commercial fungicides imazalil, tebuconazole + fluopyram, and thiophanate-M. These two potassium salts consistently inhibited mycelial growth, arthrospore germination, and germ tube elongation even at the lowest tested concentrations, while other potassium salts showed variable and generally lower efficacy. In vivo experiments on apple fruits further confirmed these findings, with potassium metabisulfite providing up to 92.48% lesion reduction in protective applications at 1.0 x 10-2 g mL-1, comparable to thiophanate-M (93.81%) and tebuconazole + fluopyram (98.47%). Notably, potassium metabisulfite outperformed imazalil, which only reached 61.36% protection at its highest concentration. In curative applications, potassium metabisulfite and phosphate achieved approximately 87% lesion reduction at 1.0 x 10-2 g mL-1, matching the performance of commercial fungicides at their recommended concentrations. Interestingly, low concentrations of potassium benzoate and carbonate increased lesion development in both protective and curative applications. These findings suggest potassium metabisulfite as a promising alternative to conventional fungicides for controlling N. dimidiatum infections, with potential applications in sustainable disease management strategies.