In 2008, there was a caveat to “How the humble potato could feed the world”. Reliance on a single crop for food security is dangerous if widespread crop failures can occur and result in famine, as happened in Ireland with the late blight epidemics of 1845, 1846, 1848 and 1849. Grain and potatoes need to complement one another for food security, and we need to prevent crop failures while also recognizing political issues. Phytophthora infestans (Mont.) de Bary, the cause of late blight, is an oomycete with two mating types and the potential for exponential production of pathogenic spores. Effective control requires an understanding of its biology, epidemiology and ability to evolve. Weather conditions suitable for blight need to be forecast. Fungicides with different chemistries need to be used in spraying regimes to prevent the spread of blight strains with insensitivity to particular modes of action. Cultivars with different broad-spectrum resistance genes are required to delay the evolution of virulent blight strains. Blight outbreaks need to be analysed for knowledge of the prevailing pathogen populations. Good farm hygiene is important because diseased tubers left lying around and volunteer plants from diseased tubers left in the ground are sources of inoculum.