ABSTRACT
This chapter focuses on the direct of climate change on the ecological features of the pathogen and their effect on the host, it should be noted that the indirect effect of climate change on pathogens through the response of host plants is also essential. It discusses one of the pathogenic fungi, the genus Rhytisma, which causes tar spot disease on Salix spp. The chapter presents the diversity and ecology of plant pathogenic fungi in the Arctic. It provides the diversity, adaptation, effect on host and ecosystem, and response to climate change of pathogenic fungi on vascular plants. The stress on host plants by environmental factors, and disturbance by biotic factors such as insects or pathogens, also tends to increase infection by pathogens. Estimation for the effect of plant pathogens at the ecosystem level is one of the most important factors to understand and manage arctic ecosystems.
