What Caused The Potato Blight In Ireland. Although scientists have known that a funguslike organism caused the potato blight that triggered the great famine in ireland in the 1840s, they didn't know. However, in the 1840s, a plant infection — potato blight, caused by the fungus phytopthera infestans — showed us how an environmental catastrophe in a vulnerable community.

The causative agent of late blight is the water mold phytophthora. Although scientists have known that a funguslike organism caused the potato blight that triggered the great famine in ireland in the 1840s, they didn’t know.