Root rot is currently the most serious disease facing raspberry producers in Europe. Diseased plants either yield very little or are killed and small areas affected by the disease can rapidly develop into very large patches, thereby rendering production uneconomic. The principal cause of root rot is Phytophthora fragariae var. rubi but other Phytophthora species are sometimes involved. At present, the disease is controlled largely by fungicides but even at relatively high levels, these can be inconsistent in their effect. Other possible control elements include growing plants on ridges and under plastic mulches but the most important element that has been identified is host resistance. Some existing cultivars already have valuable levels of resistance but the majority do not. Combining resistance with the other measures above and with reduced levels of fungicides can give satisfactory control but obtaining the necessary levels of resistance in suitable commercial cultivars will take much time and effort.