late blight of potato is caused by the fungus

1. fusarium udum
2. phytophthora infestans
3. plasmopara viticola
4. alternaria solani

Late blight is the disease that triggered the Irish potato famine of the 1840s. It also was the first plant disease for which a microorganism was proved to be the causal agent, leading to the birth of plant pathology as a science.
PATHOGEN: Phytophthora infestans