For example, Duggar (4) wrote in 1909: ". The disease triangle drawing most likely was first published by Stevens in 1960 (6), although earlier plant pathologists certainly recognized the interaction among plant, pathogen, and environment. Finally, the predominance in phytopathology of fungi, which are also highly dependent on environment, may have contributed to the development of this paradigm.
The sophisticated immune system found in mammals is absent in plants, and this places an emphasis on the host's genetic constitution. This triangular relationship is unique to phytopathology in comparison to veterinary and medical sciences because terrestrial plants possess little thermal storage capacity and their immobility precludes escape from an inhospitable environment. The three necessary causal factors of disease are positioned at the vertices. The equilateral plant disease triangle after Stevens (6). Conversely, plant disease is prevented upon elimination of any one of these three causal components.įigure 1. Thus, the figure illustrates one of the paradigms in plant pathology that is, the existence of a disease caused by a biotic agent absolutely requires the interaction of a susceptible host, a virulent pathogen, and an environment favorable for disease development (1,6). The disease triangle ( Figure 1) is one of the first concepts encountered by college students in an introductory plant pathology course (1) and often may be re-encountered in higher level classes as a fundamental principle of the factors involved in disease causation. The Disease Triangle: A plant pathological paradigm revisited. Francl Department of Plant Pathologyįrancl, L.J.
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