Impact in disease management by predicted climate change
The disease triangle is a graphical representation of a paradigm in plant pathology (Agrios 2005). It illustrates the relationship between three components of plant diseases. These components are the susceptible host, the causative biotic agent and the nature of the environment in which the two exist. If the environment is conducive for the disease causing biotic agent, then the host which is the plant is prone to adverse infection. The disease can be prevented by altering the environment in which the disease causing agent thrives in to one which is unfavorable to the disease causing agent.
The disease causal factors are placed on the vertices (Agrios 2005).
Since plants are immobile and lack the complex immune system present in animals, they are dependent on the condition of the environment for their survival (Campbell & Madden 1990; Duggar 1909). The change of environment can alter the adverse effects to either improve the host’s immunity or catalyze the pathogen virulence. If the environment is conducive for the plant which is the host, the plant might outgrow susceptibility. This though depends on the degree to which the host is affected at the onset of the disease and the changing climate.
The triangle indicates also that the three causative factors must all be present for a disease to be present (Gäumann 1950). If one of the causal factors is eliminated, then the disease ceases to exist. If the climate is conducive for a pathogen that is absent, then the disease will not occur.
A good example of climate change is when corn or maize is planted in a wet area that soon becomes dry and hot. Cercospora zea-Maydis a fungus that cause Grey leaf spot in corn cannot thrive in hot and dry weather and thus cannot cause the disease (Stevens 1960).
Agrios, G, N 2005, Plant pathology, 5th edition, Elsevier-Academic Press, San Diego, CA.
Campbell, C, L & Madden, L, V 1990, Introduction to plant disease epidemiology, Wiley
Interscience, New York.
Duggar, B, M 1909, Fungus diseases of plants, Ginn and Co., New York.
Gäumann, E 1950, Principles of plant infection, Hafner Publ, New York.
Stevens, R, B 1960, ‘Plant pathology, an advanced treatise’, Vol. 3. J.G. Horsfall & Dimond,
A,E, eds, Academic Press, New York.