Plant Pathology’s Perplexing Past – the rest of the story: Potato late blight again influences world history
Robert M. Harveson, Extension Plant Pathologist
Panhandle R&E Center, Scottsbluff
Two of the most commonly used elements for plant disease control over the years have been sulfur and copper. It was long ago observed that they both are toxic to living organisms.
The famous Bordeaux mixture was created after combining both ingredients, a brew composed of three inexpensive, easily obtainable ingredients - copper sulfate, slaked lime, and water. Its usage in the late 1870s-early1880s is credited with saving the wine industry from the downy mildew disease that was destroying vineyards across Europe. By the 1890s it was fully recognized and widely utilized as an effective method for also managing potato late blight.
Disease and World War I
Most people are also likely familiar with the infamous late blight disease of potato as a major cause of the Irish potato famine in the 1840s, and its lasting influences on world and social history. It was a major factor in the influx of Irish immigrants into the United States and Canada throughout the latter half of the 1800s. However, you may not be aware that another late blight epidemic 70 years later played a crucial role in shaping the outcome of World War I.
The Bumper Potato Crop of 1915
In July 1914, the bloodiest war in history to that point broke out in Europe between Serbia and Austria-Hungary. This drew Germany and Russia into the conflict, followed soon after by Great Britain and France as allies of Russia, and it would continue for the next four years.
The 1915 potato crop in Germany was phenomenally productive. Harvested yield was nearly three times what the German people normally needed, and more than could be consumed. This in turn created a large oversupply for feeding livestock. Things looked very promising for the coming winter and beyond indeed, as the expected quantities left over would be additionally available for conversion into alcohol.
However, an unanticipated problem appeared – a lack of sufficient storage facilities. The available warehouse space not filled with war equipment was not nearly enough to house the harvested crop. What were they to do with the tremendous surplus of potatoes?
The public then pitched in, volunteering the warm basements of public buildings and schools for storage. This mistake was quickly realized when tubers began to sprout and then rot. Waste was immense as rotting potatoes were removed and dumped into outside cull piles, setting the stage for the upcoming late blight epidemic.
The Epidemic Strikes Again
The spring of 1916 throughout central and northwestern Europe was very conducive for plant growth. The new potato crop thrived from the warm temperatures and plentiful moisture. Then suddenly the summer turned to cold rain. Cool wet weather favors the development and spread of the late blight disease.
The pathogen had survived at low levels within the masses of tubers discarded the previous year. Disease began again and swept rapidly throughout German potato fields aided by the cool, damp weather that summer.
Copper supplies were needed for military and the ongoing war. Agriculture was forced to take a back seat to the making of artillery shells; thus there was no copper to spare for making the fungicides which could have saved the potato crop.
Potatoes rotted in the fields without being harvested. What little was harvested went to the army. The soldiers were not hungry that year, but their families back home were. An estimated 700,000 German citizens died from starvation in the winter of 1916-17.
The morale and desire for continuing war by the German people plummeted in 1917. After more than three years of fighting a destructive stalemate war against the Allies, they were fatigued and demoralized. Likewise, the military weakened throughout 1917 before finally collapsing in November 1918, ending the war.
The environmental and economic conditions in Germany in 1915-16 were eerily comparable to those of Ireland in the mid-1840s (time of greatest damage from late blight), with similar, catastrophic repercussions. In both situations, farmers produced a bumper crop one year with excessive quantities of unused potatoes carelessly dumped due to lack of storage facilities. The following year was characterized by a warm spring and cool wet summer, triggering widespread crop losses due to the disease that began in the cull piles, finally culminating in famine, starvation, and human misery.
A plant disease again influences world history. Isn’t it remarkable how history repeats itself?
This article is based on the following sources:
Carefoot, G. L. and Sprott, E. R. 1967. Famine on the wind. Man’s battle against plant disease. Rand McNally and Company, 231 pp.
Horsfall, J. G., and Cowling, E. B. 1978. Some epidemics man has known. Pages 17-32 in: Plant disease, an advanced treatise, Volume II, how disease develops in populations. J. G. Horsfall and E. B. Cowling, eds. Academic Press, 436 pp.
Large, E. C. 1940. Advance of the fungi. Jonathan Cape, Ltd., 488 pp.