Salt compounds as control agents of late blight and pink rot of potatoes in storage

Each year, potato late blight [Phytophthora erythroseptica] and pink rot [PhytolAthora erythroscptica] are responsible for significant postharvest economic losses. Because of restrictions on the use of synthetic fungicides on food, there is Currently a need for less toxic, disease-controlling compounds for postharvest application. To address this need, the preventative and curative effects, as well as seed piece phytotoxicity, of various salt compounds were tested using live tubers of the potato 'Superior'. Compounds were tested as dips at the concentrations 0.002, 0.02, 0.2 mol/L and compared with a distilled water dip as a control. Tubers were inoculated with sporangia of P infestans or active zoospores of P. erythroseptica either before or after treatment with the various compounds. When concentration data were pooled and grouped means were tested for significant differences (P < 0.05). potassium sorbate, sodium metabisulfite, alum, sodium hypochlorite, copper sulfate pentahydrate, acetic acid, and Penncozeb (R) 75DF applied curatively provided disease inhibition that was significantly greater than that of the control for both late blight and pink rot. When applied as a preventative treatment, all compounds were significantly different (P < 0.05) from the untreated control in the inhibition of pink rot; however, only sodium metabisulfite, sodium hypochlorite, copper sulfate pentahydrate, and Penncozeb 75DF significantly reduced the severity of late blight. Phytotoxicity was observed when sodium hypochlorite, sodium metabisuffite, acetic acid, and copper sulfate pentahydrate were applied as seed piece treatments, at a concentration of 0.2 mol/L. Our studies suggest there is a potential for the use of selected salt compounds for control of postharvest diseases of potato.