Plant Diseases in Changing Northern Climatic Conditions

Climate change has recently been discussed widely. According to the IPCC Panel documents, the changes in temperatures are expected to be greatest in northern latitudes. Expected changes in temperatures and rainfall will make it more likely than now for some diseases to spread and survive over the winter season in northern areas. In Finland, the growing season varies between 120 and 180 days. Strawberry is the main berry crop and it is cultivated in nearly all parts of the country. It is affected by fluctuating winter temperatures, which cause root damage and plant losses. Climate change is expected to increase the importance of powdery mildews, Phytophthora species and bacterial pathogens. Colletotrichum species may also increase with changing host cultivation, and viruses can benefit from new vector populations. Phytophthora diseases, especially P. cactorum, have spread widely with plant trade. Increased use of frigo and waiting bed plants has brought more infected plants to farms and, consequently, increased fungicide use to avoid plant losses. To be able to avoid disease problems, plant resistance to P. cactorum has been evaluated of the cultivars introduced for cultivation in Finland since 1993. To estimate the risk of Colletotrichum acutatum spread and the potential for its survival in production fields, some alternate hosts have been investigated for their ability to transfer infection to strawberry in Finnish conditions. With increasing plant trade, the risk for these diseases capable of surviving in Nordic conditions has increased.