The potato famine was caused by the potato blight, a disease caused by the fungus-like microorganism Phytophthora infestans, which destroyed potato crops in Ireland starting in 1845. This blight devastated crops due to Ireland's heavy reliance on a single food source and was exacerbated by socio-political factors, such as the British government's laissez-faire policies and the continued export of other food from Ireland.

Immediate cause:

Potato blight: A devastating disease, known as late blight, was caused by the microorganism Phytophthora infestans.

Rapid spread: The blight spread rapidly through Ireland, destroying potato crops from 1845 to 1849, and continued to plague crops in subsequent years.

Crop failure: The blight caused potatoes to rot both in the ground and in storage, destroying a large portion of the crop and leading to widespread starvation.

Contributing factors:

Over-reliance on potatoes: A significant portion of the Irish population, especially tenant farmers, depended almost exclusively on potatoes for food, making them extremely vulnerable to a crop failure.

British government policy: The British government's adherence to laissez-faire economic policies meant they were slow and insufficient in their response.

Food exports: Despite the famine, other food products, such as grain, cattle, and dairy, continued to be exported from Ireland to Britain.