The purpose of this experiment was to determine the influence of temperature and fungi colonizing fruit plants on Diaporthe , a pathogenic fungus in Poland. The biotic series method was used to test in vitro the effects of the fungi colonizing fruit trees on isolates of Diaporthe . Among the 13 fungal species tested, six inhibited the growth and development of Diaporthe ; while another two species were neutral and the rest showed the lack of limiting impact in relation to the pathogen. Fungi present in the shoots of fruit plants was able to limit the growth and development of Diaporthe spp., both in chemically-protected and non-protected orchards. Studies on the effect of temperature indicated that the optimum temperature for vegetative growth of isolates of Diaporthe ranged from 20°C to 30°C, and for conidial sporulation from 25°C to 30°C. Howev - er, the ability of Diaporthe sp. to survive at extreme temperature (–20°C and +35°C) enables their vegetative growth in climatic conditions worldwide.