AbstractThe optimum conditions for growth ofRhizosphaera kalkhoffiiisolated from dead needles of Norway spruce trees affected by “top‐dying” were studied. The optimum temperature for diameter growth on malt extract, diamalt and potato dextrose agar was found to be 18°C and the fungus practically ceased growth at 24°C. Growth at 0°C was better than that at 24°C. Light had no effect on diameter growth on malt extract and diamalt agar. On malt extract agar, acidity ranging from 3.7–6.8 (after autoelaving) had no significant effect on diameter growth. Abundant pleurogenous blastospores were produced rapidly on malt extract and pycnidia as the culture aged. Pycnidia were the main sporulation type on d