Suppression of Fusarium crown and root rot of asparagus with sodium chloride

The application of sodium chloride on asparagus beds, an old practice that has been abandoned, suppressed Fusarium crown and root rot caused by Fusarium oxysporum and F. proliferatum. Spring applications of NaCl (560-1,120 kg/ha) suppressed the disease under various field conditions and were superior to KCl, KNO3, NH4NO3, or Ca(NO3)2 in retarding asparagus decline and increasing marketable yields. In the greenhouse, applications of NaCl solutions to asparagus resulted in significant increases in fresh weight and suppressed the fraction of diseased roots as well as the number of colony-forming units of F. oxysporum and F. proliferatum recovered per centimeter of root (cfu/cm). There were positive correlations between the fraction of diseased roots, cfu/cm, and the ratio of K+ to Cl- concentrations in plants that were grown in noninfested soils. Chloride uptake was negatively correlated with the fraction of diseased roots. Uptake of Na+ was restricted and not as correlated with disease suppression as was Cl- uptake. Fern analyses of field grown plants treated with NaCl confirmed the strong association between yield increases, suppression of Fusarium crown and root rot, Cl- uptake, and a K:Cl ratio in the tissue of less than 3. These applications of NaCl were not herbicidal to weed species or fungicidal to soil populations of Fusarium spp., but they did result in significant reductions of rhizosphere populations in treated plants when compared with untreated plants. Sodium chloride may suppress Fusarium crown and root rot through a fungistatic effect and/or through manipulation of host resistance