Interactions Between Sodium N-Methyldithiocarbamate and Douglas-Fir Heartwood


  • D. B. Miller
  • J. J. Morrell


Fumigants, Douglas-fir, Vapam<sup>®</sup>, decomposition, preservation


Vapam® (NaMDC) is the fumigant most commonly used to arrest and control decay of utility poles. While volatile fungitoxins are detectable only 1 to 2 years after treatment, poles treated with Vapam® remain free of decay fungi for 6 to 17 years. Vapam® decomposes to produce volatile fungicides as well as a number of nonvolatile products that may provide long-term protection. The degree and rate of decomposition of NaMDC were evaluated by using a gas chromatograph and a high-performance liquid chromatograph to analyze extracts from Vapam® mixtures with wood, cellulose, vanillin, starch and glass.

Compounds similar to those produced from Vapam®-soil mixtures were found in the mixtures tested. Of the materials identified, sulfur was the most abundant nonvolatile product in wood mixtures and may play a role in long-term wood protection. Sulfur was present only at low levels in cellulose mixtures. These results, coupled with the low levels of volatile MIT produced in the cellulose mixtures, suggest that lignin is an important site for Vapam® decomposition reactions. Further studies are suggested to determine the role of nonvolatile decomposition products in arresting decay away from the point of application.


Agrios, G. M. 1969. Plant pathology. Academic Press, New York, NY.nBenghiat, I., J. B. Bowers, G. E. Lukes, and S. Giolito. 1958. U.S. Patent 2,863,803.nElson, J. E. 1966. Fungitoxicity of sodium N-methyldithiocarbamate (Vapam) and its decomposition products. M.A. thesis, Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR.nGoodell, B. S., and R. D. Graham. 1983. A survey of methods used to detect and control fungal decay of wood poles in service. Int. J. Wood Preserv. 3(2):61-63.nHelsing, G. G., J. Morrel, and R. D. Graham. 1984. Evaluations of fumigants for control of internal decay in pressure-treated Douglas-fir poles and piles. Holzforschung 38(5):277-280.nMorrell, J. J., and M. E. Corden. 1986. Controlling wood deterioration with fumigants: A review. For. Prod. J. 36(10):26-34.nSmelt, J. H., and M. Leistra. 1974. Conversion of Metham-sodium to methylisothiocyanate and basic data on the behavior of methylisothiocyanate in soil. Pestic. Sci. 5:401-407.nThorn, G. D., and R. A. Ludwig. 1962. The dithiocarbamates and related compounds. Elsevier Publishing Co., New York, NY.nTurner, N. J., and M. E. Corden. 1963. Decomposition of sodium N-methyldithiocarbamate in soil. Phytopathology 53:1388-1394.nZahora, A. R. 1987. Interactions of the fumigant methylisothiocyanate with Douglas-fir wood and their influence on fumigant effectiveness. Ph.D. dissertation, Oregon State University, Corvallis, OR.n






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