The action of nabam, metham-sodium and other sulphur compounds on Heterodera schachtii cysts

When used in tests against eggs of Heterodera schachtii, sodium ethylenebisdithiocarbamate (nabam) solutions break down to give a number of compounds, some being hatch-inhibiting and others hatch-stimulating. The compound mainly responsible for the hatch-stimulating activity of nabam solutions is ethylenethiuram monosulphide. Stored solutions of sodium ethylenebisdithiocarbamate lose activity because the ethylenethiuram monosulphide disappears. Zinc and manganese ethylenebisdithiocarbamates were more active hatching agents than equimolar mixtures of zinc or manganese sulphates with nabam. Hatch stimulation was least with a zinc sulphate/nabam mixture of mole ratio 1.5:1, in which the dithiocarbamate ion became largely replaced by the sparingly soluble zinc dithiocarbamate. Increasing the zinc concentration in the mixture increased hatching because of the hatching activity of the zinc ion. Nabam solutions containing manganese sulphate were inactivated because the manganese ion catalysed decomposition to the hatch-inhibiting carbon disulphide. Sodium N-methyldithiocarbamate (metham-sodium, Vapam), which readily decomposed in aqueous solution, was toxic to, and prevented the hatching of, H. schachtii. Methylisothiocyanate, the major decomposition product, was toxic to H. schachtii at concentrations greater than 0.1 mM.