20 August 1845: Phytophthora infestans, a fungal infection that rots the tubers of potatoes, was recorded in Ireland on this day. David Moore, curator of the Botanic Gardens in Dublin noted that leaves of some of the potato plants in the institution were showing signs of blight. His was the first known scientific observation in Ireland of this fungus.

‘Phytophthora infestans (pronounced fy-TOF-thor-uh in-FEST-ans) is a rather common pathogen of potatoes wherever they are grown, but it is usually not a problem unless the weather is unusually cool and wet. The water is necessary for the spores to swim to infect the leaves of the potatoes; the tubers and roots of the potato are more resistant to the pathogen. The name, meaning "infesting plant destroyer" is especially appropriate, because under the right conditions and with the correct susceptibility genes in the host, Phytophthora can kill off a field of potatoes in just a few days!

Phytophthora infestans is so virulent in wet weather because it produces enormous numbers of swimming spores called zoospores in zoosporangia. The zoosporangia crack open and release dozens of zoospores. These zoospores have two flagella; a whiplash flagellum faces the back and pushes the spore through the water and a tinsel flagellum points forward and pulls the spores through the water.’

http://botit.botany.wisc.edu/toms_fungi/m2001alt.html

From such mundane sequences in the life of a fungi did the fate of a People hang in the late summer of 1845. Perhaps 30% + of the population relied on potatoes for 90% of their diet & had no ready access to any other food source. Any upset in the supply was bound to result in Calamity to a lesser or greater extent. Within weeks the Blight had swept the land and millions of Irish men women and children knew that at least a year of hardship lay ahead of them. In fact the Blight was to come back each year until 1849 and in its wake leave at least a Million dead from starvation and disease and another Million forced to flee abroad.

“The Sketch of a Woman and Children represents Bridget O’Donnel. Her story is briefly this:– ‘. . .we were put out last November; we owed some rent. I was at this time lying in fever. . . they commenced knocking down the house, and had half of it knocked down when two neighbours, women, Nell Spellesley and Kate How, carried me out. . . I was carried into a cabin, and lay there for eight days, when I had the creature (the child) born dead. I lay for three weeks after that. The whole of my family got the fever, and one boy thirteen years old died with want and with hunger while we were lying sick.'”

THE ILLUSTRATED LONDON NEWS. [Dec. 15, 1849.]

(From our own Correspondent.)

https://viewsofthefamine.wordpress.com/illustrated-london-news/condition-of-ireland/