This summer, as every summer, my neighbors do battle with Phytophthora infestans, the potato blight fungus. I see them walking their ridges, a tank of fungicide on their backs, sprayers in hand. It's touch-and-go as to who will win -- the gardener or the invisible invader.
In the 19th century, Phytophthora infestans directly or indirectly caused the death of a million Irish people and sent millions more on a great diaspora to Britain, Australia, New Zealand and America. How did it happen?
The potato originated in the Andes highlands of South America, and was introduced into Ireland by the English. It flourished in the cool, moist Irish air, and adapted readily to the poor soils of Western Ireland where a large part of the native population had been driven by English colonizers. The potato required no more than a spade for its cultivation and a pot for its consumption, and was therefore eminently suitable for a people rendered abjectly poor by British conquest and perfidy.
The fungus that caused the Great Irish Famine, like the potato itself, was a New World import. It is believed to have originated in Mexico, and somehow made its way to the United States, where it found an ideal host -- the domesticated potato. It crossed the Atlantic in a ship's stores, arriving in June 1845 in southern Britain. By August, blight had destroyed crops in every European country.
The effects of the fungus were more severe in parts of Ireland than elsewhere because of the almost exclusive dependence upon the potato as food, and because crowding and impoverishment made Irish people easy victims of cholera, typhus, and other diseases that followed in the wake of famine.
It was not until the 1920s that the invention of effective fungicides finally brought Phytophthora infestans under control. So why did massive famine not recur in Ireland during the long decades between the mid-1800s and the invention of fungicides?
Part of the answer is visible from my window, out there across Dingle Bay. In 1858, the first Atlantic telegraph cable was brought ashore at Valentia Island, and suddenly the world became a smaller place. News crossed the oceans in seconds, not weeks, and the consequences of British policy in Ireland would henceforth be monitored by the world, and particularly by the increasingly influential Irish diaspora. The situation was not unlike the way FaceBook and YouTube changed the dynamic of the recent upheavals in Iran.