Agriculture Reference
In-Depth Information
CHAPTER 17
POTATO LATE BLIGHT
EDUARDO S.G. MIZUBUTI AND WILLIAM E. FRY
17.1 INTRODUCTION
Potato late blight caused by the oomycete
Phytophthora infestans
(Mont.) de Bary
may be the best known, longest studied, and still among the most destructive of all
plant diseases. Devastation caused by this plant pathogen in the late 1840s in
Europe, led to food shortages throughout Europe, but the effect in Ireland led to the
Irish potato famine. The enormity of the famine initiated by this plant disease
stimulated much investigation on plant diseases and led to the development of plant
pathology as a distinct discipline. However, these studies had much broader impact.
Inoculation experiments by de Bary provided evidence for the causal role of this
pathogen in the disease and contributed to the later acceptance of Pasteur's more
general germ theory of disease.
Late blight impacts humans because the foliar phase limits production of tubers;
infections on tubers destroy a potential food source and tremendous effort and
resources are employed to prevent both of these phases. The human suffering
resulting from the dramatic epidemics in the 1840s was exacerbated by the shortage
of potatoes. Early 19
th
century Ireland had developed a 'potato economy' in which a
large, poor population depended almost exclusively on potatoes for their subsistence
for most of the year (Bourke, 1993). The high productivity of potatoes permitted a
population explosion in Ireland and some have estimated that the Irish population
nearly tripled during the 60 years prior to 1840 (Woodham-Smith, 1962). The
starvation that resulted from the food shortages caused by the blight epidemics led to
the deaths and emigration of an estimated three million people (Large, 1940). A
second famine caused by late blight was experienced in Germany during 1916 and
1917. The shortage of copper, the basic constituent of Bordeaux mixture, was
caused by the demanding armour industry. Because late blight control was not
properly carried out, potato availability for the families of soldiers was short. Many
died and this affected the morale of the German troops. Some historians speculate
this could have led to the defeat of the Germans in World War I (Horsfall and
Cowling, 1978).
Knowledge of the etiology and epidemiology of the disease and discovery and use
of fungicides, enabled improved suppression of late blight during the 160 years
following the Irish potato famine. However, despite the improved disease suppression,
the financial impact remained burdensome. Economists at the International Potato
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