IN VITRO EFFECTIVENESS OF DISINFECTANTS ON GEOTRICHUM CITRI-AURANTII SPORE VIABILITY

Sour rot caused by Geotrichum citri-aurantii is an important citrus postharvest disease in Uruguay. Disease management is currently achieved using sodium ortho-phenylphenate (SOPP) and 9-Aza-1,17-diguanidinoetadecane (Guazatina), however, these fungicides leave residue on fruit at levels generally unacceptable for international markets. Alternative control methods are necessary and here we explored the effect of various disinfectants on Geotrichum spore viability in vitro in comparison with SOPP. Disinfectants tested were: 200 ppm sodium hypochlorite, 100 ppm stabilized chlorine dioxide at pH 6 and 6.5, 5000 ppm N-chloro tosylamide (sodium salt), 1600 ppm didecyl dimethyl ammonium chloride/alkyl amido propyl chloride dimethyl benzyl ammonium chloride, 120 ppm didecyl dimethyl ammonium chloride and 20000 ppm SOPP. Suspensions of 1×106 spores/ml were immersed in solutions of each treatment for 1, 2 or 4 min. The most efficient treatments were quaternary ammonium derivatives and chlorine dioxide at pH 6, compounds that killed 100% of the spores for the three exposure times. Sodium hypochlorite killed 97 and 100% of the spores at 2 and 4 min, respectively. Chlorine dioxide at pH 6.5 killed 99.8 and 100% at 2 and 4 min exposure, respectively. SOPP did not provide a satisfactory control when used under these conditions.