Control of Bacterial Soft Rot in Potato Tubers with Hypochlorite and Certain Organic Acids

Abstract

The severity of bacterial soft rot in potato tubers after 96 h in a mist chamber at 20C was reduced by 86% when freshly-harvested tubers were submerged in an aqueous suspension of Erwinia carotovora pv carotovora (5 × 106 cfu/ml) for 5 min, removed, submerged in a 1% solution of citric acid for 5 min and then air-dried prior to incubation. Other organic acids that significantly reduced disease severity in similar tests included malonic, ascorbic, and acetic. Salts of these acids either had no effect or much less effect on soft rot severity than did the parent acid. Sodium cinnamate provided as much control as did citric acid. Treatment with hypochlorite at concentrations up to 10,000 ppm Cl2 equivalents reduced disease severity up to 99%, whereas 250 to 1000 ppm reduced the severity up to 90%. Both the acids and hypochlorite were much less effective when bacteria had been infiltrated into lenticels. Soft rot severity usually was increased when treatment solutions were infiltrated into lenticels. The level of control provided by treatment with hypochlorite at 1000 ppm was less than that provided by treatment with an experimental compound (CIBA GEIGY No. 78039) that is highly toxic to soft rot Erwinia spp (minimum inhibitory concentration = 1 ppm).KeywordsCitric AcidOrganic AcidPlant PathologyMinimum Inhibitory ConcentrationPathogenic BacteriumThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.