The Irish Famine of 1740-1741  in the Kingdom of Ireland, was estimated to have killed between 20% and 38% of the 1740 population of 2.4 million people, the  upper estimate a proportionately greater loss than during the worst years of the Great Famine of 1845-1852. The famine of 1740-41 was due to extremely cold and then rainy weather in successive years, resulting in food losses in three categories: a series of poor grain harvests, a shortage of milk, and frost damage to potatoes. At this time, grains, particularly oats, were more important than potatoes as staples in the diet of most workers. Deaths from mass starvation in 1740-41 were compounded by an outbreak of fatal diseases. The cold and its effects extended across Europe, but mortality was higher in Ireland because both grain and potatoes failed. This is now considered by scholars to be the last serious cold period at the end of the Little Ice Age of about 1400-1800. By the mid-19th century's better-known Great Famine of 1845-1852, potatoes made up a greater portion of the Irish diets, with adverse consequences when the crops failed. This famine differed by "cause, scale and timing:" it was caused by an oomycete infection which destroyed much of the potato crop for several years running. The crisis was exacerbated by insufficient relief and extreme government regulations.
Question: What hurt the potatoes
Answer: oomycete infection