On September 9, 1845, Irish newspapers reported for the first time that there was a famine in Ireland. At that time, the population of Ireland was 8,295,000. By 1851, there were fewer than six million people remaining there. From the time of the Dublin Evening Post's first report of a "disease in the potato crop," until recovery was established, more than one and a half million people died of starvation and disease, while hundreds of thousands of others had emigrated to Canada and America.
It was in the late summer of 1845 that a fungus from North America (Phytophthora infestans) infested the potato crop of Ireland, destroying forty percent of the crop. The following year, the fungus destroyed one hundred percent of the crop.
This period in Irish history has been referred to, particularly by the British, as "The Great Hunger" or "The Great Famine." The more acceptable revisionist (and apologist) viewpoint is that the starvation resulted from the weather, the fungus, overpopulation, and a colonial system that made the Irish dependent on the potato.
The World Book Encyclopedia has the following entry for "The Potato Famine":