Potato blight and the Irish famine

Potato blight and the Irish famine

  • In about 1800, the potato, which was introduced in Europe from South and Central America around 1570 a.d., was a well-established crop in Ireland.
  • After strong objections against adopting it because:
    1.  It was new and not mentioned in the Bible.
    2.  It was produced in the ground and, therefore, was unclean.
    3.  Because parts of it were poisonous, the potato was nevertheless adopted and its cultivation spread rapidly.
  • Adoption of potato cultivation came as a result of it producing much more edible food per unit of land than grain crops, mostly wheat and rye, grown until then.
  • It was adopted also because the ground protected it from the pests and diseases that destroyed aboveground crops and from destruction by the soldiers sent by absentee English landlords to collect overdue land rents.
  • At that time, most Irish farmers were extremely poor, owned no land, and lived in small windowless, one-room huts.
  • The farmers rented land from absentee English landlords who lived in England, and planted grain and other crops.
  • The yields were poor and, in any case, large portions of them had to be used for paying the exorbitant rent so as to avoid eviction.
  • The Irish farmers also kept small plots of land, usually as small as a quarter of an acre and basically survived the winter with the food they produced on that land.
  • Potato production was greatly favored by the cool, wet climate of Ireland, and the farmers began growing and eating potatoes to the exclusion of other crops and foodstuffs.
  • Irish farmers, therefore, became dependent on potatoes for their sustenance and survival.
  • Lacking proper warehouses, the farmers stored their potato tubers for the winter in shallow ditches in the ground.
  • Periodically, they would open up part of the ditch and remove as many potatoes as they thought they would need for the next few weeks.
  • The potatoes grew well for many years, free of any serious problems.
  • In the early 1840s, potato crops began to fail to varying extents in several areas of Europe and Ireland.

The late blight of potato and the Irish famine

  • Most of the growing season of 1845 in Ireland was quite favorable for the growth of potato plants and for the formation of tubers.
  • Everything looked as though there would be an excellent yield of potatoes everywhere that year.
  • Then, the weather over northern Europe and Ireland became cloudy, wetter, and cooler and stayed that way for several weeks.
  • The potato crop, which until then looked so promising, began to show blighted leaves and shoots, and whole potato plants became blighted and died.
  • In just a few weeks, the potato fields in northern Europe and in Ireland became masses of blighted and rotting vegetation.
  • The farmers were surprised and worried, especially when they noticed that many of the potatoes still in the ground were rotten and others had rotting areas on their surface.
  • They did what they could to dig up the healthy looking potatoes from the affected fields and put them in the ditches to hold them through the winter.
  • The farmer’s worry became horror when later in the fall and winter they began opening the ditches and looking for the potatoes they had put in them at harvest.
  • Alas, instead of potatoes they found only masses of rotting tubers, totally unfit for consumption by humans or animals.
  • The dependence of Irish farmers on potatoes alone meant that they had nothing else to eat  and neither did any of their neighbors.
  • Hunger was quickly followed by starvation, which resulted in the death of many Irish.
  • The famine was exacerbated by the political situation between England and Ireland.
  • The British refused to intervene and help the starving Irish with food for several months after the blight destroyed the potatoes.
  • Eventually, by February of the next year (1846), food, in the form of corn from the United States, began to be imported and made available to the starving poor who paid for it by working on various government construction projects.
  • Unfortunately, the weather in 1846 was again cool and wet, favoring the potato blight, which again spread into and destroyed the potato plants and tubers.
  • Hunger, dysentery, and typhus spread among the farmers again, and more of the survivors emigrated to North America.
  • It is estimated that one and a half million Irish died from hunger, and about as many left Ireland, emigrating mostly to the United States of America.
  • The cause of the destruction of the potato plants and of the rotting of the potato tubers was, of course, unknown and a mystery to all.
  • The farmers and other simple folk believed it to have been brought about by “the little people,” by the devil himself whom they tried to exorcise and chase away by sprinkling holy water in the fields, by locomotives traveling the countryside at devilish speeds of up to 20 miles per hour and discharging electricity harmful to crops they went by, or to have been sent by God as punishment for some unspecified sin they had committed.

The late blight of potato and the Irish famine

  • The more educated doctors and clergy were so convinced of the truth of the theory of spontaneous generation that even when they saw the mildewy fungus growth on affected leaves and on some stems and tubers, they thought that this growth was produced by the dying plant as a result of the rotting rather than the cause of the death and rotting of the plant.
  • Some of the educated people, however, began to have second thoughts about the situation. Dr. J. Lindley, a professor of botany in London, proposed incorrectly that the plants, during the rains, over absorbed water through their roots and because they could not get rid of the excess water, their tissues became swollen and rotted.
  • The Reverend Dr. Miles Berkeley, however, noticed that the mold covering potato plants about to rot was a fungus (oomycete) similar but not identical to a fungus he observed on a sick onion.
  • The fungus on potato, however, was identical to a fungus recovered from sick potato plants in northern Europe.
  • Berkeley concluded that this fungus was the cause of the potato blight, but when he proposed it in a letter to a newspaper, it was considered as an incredible and bizarre theory unsupported by facts.
  • The puzzle of what caused blight of potato continued unanswered for 16 years after the 1845 destruction of potatoes by the blight.
  • Finally, in 1861, Anton deBary did a simple experiment that proved that the potato blight was caused by a fungus.
  • DeBary simply planted two sets of healthy potatoes, one of which he dusted with spores of the fungus collected from blighted potato plants.
  • When the tubers germinated and began to produce potato plants, the healthy tubers produced healthy plants, whereas the healthy tubers dusted with the spores of the fungus produced plants
    that became blighted and died.
  • No matter how many times deBary repeated the experiment, only tubers treated with the fungus became infected and produced plants that became infected.
  • Therefore, the fungus, which, we know now, is an oomycete was named Phytophthora infestans (“infectious plant destroyer” from phyto = plant, phthora = destruction, infestans = infectious), was the cause of the potato blight.
  • DeBary also showed that the fungus did not just reappear from nowhere the following growing season but instead survived the winter in partially infected potato tubers in the field or storage.
  • In the spring, the fungus infected young plants coming from these partially rotten tubers, produced new spores on these plants, and the spores then spread to other cultivated potato plants that were
    infected and killed.
  • With this experiment deBary actually disproved the theory of spontaneous generation, which stated that microorganisms are produced spontaneously by dying and dead plants and animals, and ushered in the germ theory of disease.
  • The honor for this proof, however, is reserved for Louis Pasteur, who proved the theories while working with bacteria at about the same time, 1861–1863, that deBary published his work with the potato blight fungus.

Potato blight and the Irish famine

 

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