The highlands of central Mexico are considered by many to be the centre of origin of P. infestans, although others have proposed its origin to be in the Andes, which is also the origin of potatoes. The first record of "Black Potato" was made in 1751. In September 1845 a blight struck the potato crop in Ireland. It is thought that the disease travelled to Europe on trade ships from the US where it struck in 1843 and 1844. It first spread to England and then to the South east of Ireland. Blight caused the potato foliage to wither and the potatoes went black and rotted in the ground. Between one-third and half of the potato crop was destroyed. The price of potatoes more than doubled over the winter: a hundredweight (50kg) of potatoes rose in price from 16p to 36p. The 1846 harvest failed completely and this destroyed the main crop and also the seed potatoes needed for the planting in 1847. In 1847, the harvest was somewhat better due to slightly drier weather. In 1848 and 1849 blight again struck badly causing a second period of famine. In 1850 the harvest was better and blight after this never happened on the same scale. It was not until 1882, almost 40 years after the famine, that scientists discovered a cure for Phytophthora Infestans: a solution of copper sulphate sprayed before the fungus had taken hold.
