CHAPTER 2: Modes of Action of Fungicides

The mode of action of a fungicide describes how the active ingredient affects the fungal pathogen. Depending on the fungicide, mode of action may be described at several different physiological levels including morphological changes, affected cellular components or biochemical processes, and sites of molecular activity. The extent of our understanding of mode of action varies with different active ingredients. Where knowledge is limited, such as with the dicarboximide fungicides (iprodione and vinclozolin), mode of action is most often described in terms of the observed changes in fungal morphology and growth in laboratory cultures. In other cases, such as the benzimidazole fungicides (thiophanate-methyl), research has uncovered the exact molecular site of activity. Because mode of action is related to other issues (especially fungicide resistance), researchers continue to explore the fundamentals of how fungicides affect target pathogens. A more thorough understanding of fungicide mode of action will help prepare turf managers to deal with issues such as efficacy against new or emerging diseases and complications brought on by the development of fungicide-resistant strains in pathogen populations.