STUDIES ON THE MECHANISM OF FUNGICIDAL ACTION OF METALLIC ETHYLENEBISDITHIOCARBAMATES

Abstract

The titration reactions between zinc, manganese, and iron sulphates and nabam were studied. Except for possibly those with manganese, they were found to involve more than simple precipitations. Manganese ethylenebisdithiocarbamate was found to be relatively water soluble and easily converted to ethylenethiuram monosulphide (E.T.M.) on aeration. The corresponding-pure zinc salt was highly insoluble in water. Aqueous suspensions were relatively non-fungicidal and failed to yield E.T.M. on aeration. Corresponding suspensions in dilute alkali, however, showed increased solubility and fungicidal activity. They converted readily on aeration to a yellow fungicidal product containing E.T.M. The conversion of E.T.M. to an isothiocyanate was demonstrated. It is concluded that the mode of fungicidal action of the zinc and manganese salts is the same as that of the parent nabam. The same mechanism is probably involved with the iron salts. The practical implications of the work and its bearing on the recent isothiocyanate theory are discussed.