Phytophthora

Phytophthora infestans is a water mold, a fungus-like protist historically misclassified as a true fungus, that causes late blight, a fast-spreading disease of potato and tomato plants that destroys leaves and rots tubers in wet, cool conditions. It was the direct cause of the Irish potato famine of the 1840s, when repeated crop failures triggered mass starvation and emigration, and it remains one of the most economically damaging plant pathogens in the world, continuing to threaten potato production on every continent where the crop is grown today.