The toxicity of certain sulphur compounds to Synchytrium endobioticum, the fungus causing wart disease of potatoes

Summary. The toxieities towards the winter sporangia of Synchytrium endobioticum of certain of the simpler sulphur compounds which are at all likely to be formed when sulphur is added to soil were tested and compared with that of sulphuric acid. Sulphuric (H2SO4), sulphurous (H2SO3), dithionic (H2S2O6), trithionic (H2S3O6), tetrathionic (H2S4O6), and pentathionic (H2S5O6) acids were toxic and this toxicity was of the same order in each case at the same hydrogen ion concentration. Their neutral salts were non-toxic. These facts suggest that the toxicities of these acids are mainly due to their hydrogen ion concentrations. Acidified solutions of sodium thiosulphate Na2S2O3, sodium hydrosulphite Na2S2O4 and sodium formaldehyde sulphoxylate were about ten times as toxic as sulphuric acid. Evidence is brought forward which suggests that the toxicity of these acidified solutions, in excess of that accounted for by the hydrogen ion concentration, is due to the thiosulphuric acid present in each of them. In view of the experimental difficulties due to the instability of some of the compounds and the length of time taken by them to exert their toxic action on the fungus investigated, this conclusion must be regarded as tentative. Of the other compounds tested sodium hydroxide was found to be a little more toxic than sulphuric acid and persulphuric acid about ten times as toxic; hydrogen peroxide, calcium polysulphide and sulphuretted hydrogen were only slightly toxic