ASCOSPORE PRODUCTION PERIOD OF PHACIDIUM INFESTANS, A SNOW BLIGHT FUNGUS ON PINUS-SYLVESTRIS

Ascospore production of Phacidium infestans was monitored during two a utumns in 1971 and 1974. Monitoring was done using recording spore tra ps, with excised branches of Scots pine that had been naturally infect ed during the previous winter as the spore source. Spore production be gan in September and continued until the snow covered the spore source in November or spore production capacity was exhausted in December. T he highest spore counts were obtained in October. Relative humidity, t emperature and precipitation hours correlated positively, and direct s olar radiation hours negatively, with the number of spores. In regress ion analysis, however, the daily average relative humidity was the onl y significant independent variable explaining the daily number of spor es.