LIBERATION OF HETEROBASIDION-ANNOSUM CONIDIA BY AIR-FLOW

The effect of speed and humidity of che airflow and the mist sprayed w ith airflow on the liberation of conidia of Heterobasidion annosum fro m pure cultures was studied in a small windtunnel. The conidia were li berated more easily in humid than in dry airflow. Liberation was most abundant when mist was added to the airflow. Threshold speed for the l iberation of conidia was calculated to vary between 1.8 m/s and 3.9 m/ s. According to the results, conidia of H. annosum may be liberated in to the air by wind gusts associated with high humidity or mist and thu s the conidia may have a role in aerial dispersal, although this is pr obably small compared with basidiospores.