During the mid-1800s, an event called the Great Famine occurred in Ireland. This event was caused by the organism phytophthora infestans, commonly known as potato late blight, which infected the farmer's potatoes, rendering them inedible. During this time, P. infestans left many people suffering or even dead due to lack of food. This article will cover various topics about the famine, such as how it came to Ireland, the potato, the effects of the famine on the Irish people, and the people's dependence on potatoes. The Great Famine was a national tragedy for Ireland and caused mass devastation in the country. Many researchers believe that the first major movement of P. infestans occurred in the 1840s. There were reports of infected potatoes in Philadelphia starting in 1843. Potato blight spread to the northeastern United States, the Midwest, and Canada by 1845. In June 1845, a new disease was observed occurring on farmer's potatoes in Belgium. Already in October 1845 P. infestans had spread to Germany and even Ireland. The researchers believe there are two possible ways the protist traveled from North America to Europe. It is speculated that it came from Mexico to Europe or began in Mexico, moved to the United States, and finally made its way to Europe. There is a high possibility that the disease has spread worldwide through the international trade of potatoes from the European region. Most of the infected potatoes were easily detected, but some were not. Potatoes grown in cool regions of Europe were less likely to contract the virus unlike potatoes grown in areas such as Africa, ...... middle of paper ......, SB, Dyer, AT , Matuszak, J.M., Drenth, A., Tooley, P.W., et al. (1993). Historical and recent migrations of Phytophthora infestans: chronology, pathways and implications. Mann, C. C. (2011, November). How the potato changed the world. Retrieved January 8, 2014, from Smithsonian: http://www.smithsonianmag.com/history-archaeology/How-the-Potato-Changed-the-World.htmlMintz, S., & McNeil, S. (2013). The Irish Potato Famine. Retrieved January 8, 2014, from Digital History: http://www.digitalhistory.uh.edu/historyonline/irish_potato_famine.cfmPurcell, T. (1996, May 10). Irish potato famine and trade (history). Retrieved January 13, 2014, from American.edu: http://www1.american.edu/ted/POTATO.HTMStork, E. (n.d.). British policies during the Great Famine. Retrieved January 13, 2014, from mtholyoke.edu: http://www.mtholyoke.edu/~ebstork/famine.html#anchor2748030