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​​​The Irish Potato Famine and the Birth of Plant Pathology

An Illustrated chapter
from Plant Diseases: Their Biology and Social Impact
by Gail L. Schumann


In the early summer of 1845, the days were sunny and the potato crop was growing well. There was no warning of the disaster that would strike, causing misery, suffering, and death. Then, the weather turned overcast and rainy for weeks, and the potato plants rotted as the Irish peasants watched helplessly. The horrors of the Irish potato famine are still remembered--one more wedge between the English and Irish, contributing to political conflicts that continue to this day.

The story of this disaster is an important one. It introduces many of the ideas to be presented in this text, including the political aspects of food supply, the risks of genetic uniformity and dependence on only a few food crops, and the distribution of new crops from their origins throughout the world. But these same concepts could be derived from nearly any agricultural failure. The Irish potato famine is of specific importance because the debate surrounding the study of the stinking mass of rotted potatoes gave birth to the science of plant pathology. Infectious microorganisms were finally to be accepted as causes of disease rather than its result, predating even Pasteur's work with bacteria. The theory of spontaneous generation of microorganisms from decaying tissues was soon to be replaced with the germ theory.

This idea is so commonly accepted today that we assume that a disease is caused by "germs" unless proven otherwise. Today's mysterious problem diseases are those that do not appear to be caused by bacteria, fungi, viruses, and other less familiar pathogens. In the mid-1800s, however, most people viewed disease, whether in plants, animals, or people, as the result of bad weather, or punishment from God, or perhaps just bad luck.

The Arrival of the Potato in Europe

The Potato Plant

The Components of the Epidemic

The Birth of Plant Pathology

Protecting Potatoes from the Blight

Lessons from the Potato Famine

Selected Readings