As potato cultivation spread around the world, so did the many pests and pathogens that can attack both growing plants and stored tubers. Some of the potatoes that were taken from one country to another carried pests and diseases within their tubers, on the surface of their tubers, and in the soil attached to their tubers. Ships provided a global network for their spread. Saving tubers to plant the next crop exacerbated the problem. Some pests and diseases became major problems globally, others were of more local concern, and yet others of only minor significance; this could change with global warming. Disease-free planting material is essential if potato crops are going to deliver the yield and quality of tubers required of a food security crop. Statutory seed certification schemes for the multiplication of seed tubers and propagation through true potato seed (TPS) are two important ways of achieving this objective. Resistance genes are available and could be more widely deployed for vector-borne viruses and soil-borne nematodes and wart disease (caused by a fungus). However, it is also clear that wherever potatoes are grown and tubers stored, they will be under attack from various pests and diseases.