Basidiocarp development and spore release by Stereum purpureum in the field

Abstract

A Hirst spore trap was operated for 1 year in the centre of a dying apple tree bearing numerous basidiocarps (sporophores) of Stereum purpureum. Sporophores were produced mainly in autumn and winter on dead branches which were alive the previous spring and summer; they did not develop while branches were still leafing, or on old dead branches. Once produced, individual sporophores shed spores during suitable weather for at least 8 months.

The main climatic factor associated with spore release was rain. Spores were released when the relative humidity rose above approximately 90% after rain, and fell to zero after the relative humidity fell below this level; they were not shed after dew. Significant numbers of spores were caught on 90.6% of the days when rain fell, and on 62.2% of the days the trap was operated. Spores were shed during the day and at night, although more frequently at night. There was little difference in the number of rain and spore-release days in the different seasons. Duration of continuous spore showers ranged from < 1 to 29h.