A blight is a plant disease, particularly one caused by a fungus. If conditions are cold and wet, they release spores that enter the plant. Shortly after farmers would dig up the potatoes, they would begin to rot and decay. These were rotten potatoes, inedible and unable to feed the starving Irish. In the first year of the famine, about a third of the potato crop was lost. About three-quarters of the potato crop was lost in both of the following two years. Scientists discovered that the same potato disease that had affected Ireland also affected Canada in 1844 and the United States of America in 1843 and 1844. “The disease is thought to have traveled to Europe on merchant ships and spread spread to England and finally to Ireland, first affecting the south-east (Abbot,