A stable concentrated solution of a metam salt and a polysulfide, particularly calcium polysulfide, can be used to treat for soil pathogens, including the pathogen responsible for potato early die. Calcium polysulfide alone in sufficient concentration and dosage provides activity against the same pathogen. It is believed that the high concentrations of the compounds, that is, the high concentration of lime sulfur admixed with a metam, results in lower rates of degradation that result from calcareous soil, increased soil adsorption or retention, and improved distribution of metam or methyl isothiocyanate (MITC) in the soil.