The Botanical Review

, Volume 15, Issue 9, pp 629–643

The nature of the fungicidal action of copper and sulfur

  • S. E. A. McCallan
Article

DOI: 10.1007/BF02861716

Cite this article as:
McCallan, S.E.A. Bot. Rev (1949) 15: 629. doi:10.1007/BF02861716
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Conclusions

In summarizing available information on the mechanism of the fungicidal action of copper it appears most likely that exudates, such as hydroxy and amino acids, produced from fungus spores react with the “insoluble” copper fungicides to form soluble toxic copper complexes. These copper complexes exert the direct fungicidal action and vary in composition, depending on the original fungicide and probably also the fungus. While this is the primary fungicidal action, it is supplemented by the copper brought into solution by atmospheric agencies and host plant exudates. These two agencies, however, likely play the most important role in phytotoxicity or host plant injury. Finally cumulative action is also a supplementary factor, though perhaps indistinguishable from and a part of the action by spore secretions or exudates.

In the case of the sulfur fungicides the various theories of mechanism of action are more or less mutually exclusive. The evidence favors action at a distance by means of the vapor, and that the vapor can react with the spore or other plant tissue to produce hydrogen sulfide, the active toxic agent. Hydrogen sulfide produced by action of the plant is probably of importance only in phytotoxicity.

The dosage-response curve is a valuable tool in the interpretation of the nature of fungicidal action and should aid in a better understanding of this intricate mechanism.

Copyright information

© The New York Botanical Garden 1949

Authors and Affiliations

  • S. E. A. McCallan
    • 1
  1. 1.Boyce Thompson Institute for Plant Research, Inc.N. Y.

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