Tag Archives: potato crop failure

The Irish Potato Famine Pathogen

The first MEMF post of 2015 is dedicated to the potato destoryer: Phytophthora infestans  (phyto = plant, phthora = destroyer) – causal agent of the Irish potato famine.

For me, the past two weeks – from Christmas Eve to New Years – have been a gigantic food parade with roasts, dumplings, cakes and Christmas cookies marching by in endless rows. Hunger is very far away from me these days. And yet, less than 200 years ago Europe was struck with one of its worst famines.

Late Blight disease of potatoes

During the Irish potato famine more than 1 million people died and almost 2 million emigrated from Ireland in a period of just five years. The famine was brought about by two year of potato crop failure due to Late Blight disease caused by the oomycete Phytophthora infestans (pronounced fy-TOF-thor-uh in-FEST-ans). What on earth is an oomycete?, you might wonder now. An oomycete is a microbe, which at first sight resembles a fungus with its filamentous growth and spore production. But oomycetes differ from fungi in many aspects: their cell walls are made of cellulose (like plants and algae) and not chitin (like fungi) and the oomycete spores, called zoospores, can swim. The swimming zoospores are the reason why Late Blight disease becomes epidemic during prolonged wet and cold periods.

The first symptoms of Late Blight disease are small black/brown lesions on potato leaves and stems that appear water-soaked. These lesions soon expand and become necrotic. In humid conditions, Phytophthora produces sporangia that are visible as white growth at the edge of the lesions on the lower leaf surface. Sporangia can be dispersed by air or splashed by raindrops, but generally do not survive long-distance travel. When the temperature drops below 15 °C, the Phytophthora sporangia produce the swimming zoospores that spread infection by moving through water on the potato surface and waterlogged soil to infect plants and tubers. Shallow, brownish or purplish lesions appear on the tuber surface after infection. Secondary infections with other microbes subsequently reduce the tuber to a stinking, rotten potato soup.

The Irish potato famine – starving in the midst of plenty

The European weather in September 1845 was unusually cool and wet and allowed easy distribution of the Late Blight pathogen, which can destroy a potato field in less than two weeks. The disease struck again in the following year, leaving the potatoes rotting in the ground and obliterating the primary food source for millions. All over Europe, the potato yield losses led to the “hungry ‘40s”, but no country was hit as hard as Ireland.

The reason for this was demographics. In Ireland, English lords leased their land to English middlemen, who divided the land in small parcel and rented them to Irish tenants. The tenants paid the high rent in the form of produce: grains and sometimes pigs. To fill their own stomachs, they depended entirely on potatoes. When the potato crop failed in 1845 and 1846, the poor tenants were left with nothing to eat.

Between 1845 and 1860 more than 1 million people died of starvation or disease. The worst thing was that Ireland was perfectly able of producing large quantities of food during these years. Only a single crop – the potato – had failed.

Most tenants continued to grow other crops, but they were caught in an impossible bid – they had to sell these crops to pay their rent or face eviction. While people were starving and dying, Ireland continued to export food virtually unabated.

The dramatist George Bernard Shaw refers to the years of suffering in his play, Man and Superman (1903):

VIOLET. The Famine? 

MALONE [with smouldering passion] No, the starvation. When a country is full o food, and exporting it, there can be no famine. Me father was starved dead; and I was starved out to America in me mother’s arms. English rule drove me and mine out of Ireland.

Private charities and religious organisations like the Society of Friends, or Quakers, from America, tried to provide food, mostly flour, rice, biscuits and set up soup kitchens, which were the most successful relief measure of all, but were to few to stop the hunger.

The Choctaw Donation

The most memorable gift to the Irish tenants was a donation of $170- the equivalent of about $5000 today – by the Choctaw tribe of American Indians in 1847. They had a special affinity with the hungry and those who had lost their homes, since it was only 16 years since their tribe had been made homeless and walked the “Trail of Tears” from Oklahoma to Mississippi, along which many of them died. The amount was small, but this extraordinary gift from a people who were themselves terribly impoverished has never been forgotten.

Emigration to America on the ‘coffin ships’

Many of the starving Irish tried to escape to other countries. Around 2 million people left Ireland – mostly to the east coast of the United States. Ireland has never recovered from this demographic watershed and remains the only country in Europe with a smaller population today than it had in 1840.

The emigrants were regarded as the lucky few, but the journey on the overcrowded ships was dangerous and so many people died that the migration ships were called ‘coffin ships’. In the US, the Irish immigrants were not welcomed with open arms. Cartoons soon circled around that depicted the Irish as brutish, simian, bellicose and always drunk. The immigrants took whatever unskilled jobs they could find, working on the docks, pushing carts, or digging canals and labouring on the railroads. Their lives were hard, mortality rates remained high and many of them turned to crime out of boredom, desperation and anger, which only exacerbated the public perception of them as troublemakers and public scourges. It took many years before the Irish immigrants were fully integrated in the US society and the great-grandson of a farmer from County Wexford, who had left Ireland in 1849, became the 35th President of the United States: John F. Kennedy.



http://botit.botany.wisc.edu/toms_fungi/m2001alt.html, http://www.britannica.com/EBchecked/topic/294137/Irish-Potato-Famine, http://www.dochara.com/the-irish/food-history/the-irish-potato-famine-1846-1850/, http://immigrationinamerica.org/528-great-irish-famine.html