In 1875, Smith published a paper describing and illustrating the overwintering spores of "Phytophthora infestans", the causal agent of late blight of potatoes, the disease responsible for the Great Famine of Ireland. For this he was awarded the Royal Horticultural Society's Knightian gold medal. The German mycologist Anton de Bary pointed out that Smith had actually described some contaminating spores, but national pride upheld Smith's reputation as a plant pathologist and he was appointed to several governmental commissions on plant diseases, as well as publishing a book on the subject in 1884.