Take-off of Mould Spores in Relation to Wind Speed and Humidity

Using horizontal tube-cultures of various moulds belonging to the genera Thamnidmmt, Phymatotrichum, Trichotheciwm, Ptptocephalis, Trichoderma, Mucor and Mycogone, the take-off of dispersal units (usually spores) under the influence of air currents of various speeds and of different humidities has been studied. It is found that in all the dry-spore forms the number of spores set free increases as the speed of the air stream rises. Further, at any given air-stream rate, the numbers of spores set free are greatest in the first interval of time and rapidly fall off in subsequent intervals. In all species, spores are more readily set free in air streams of relatively low as compared with those of relatively high humidity. Although Trichoderma viride has been regarded as a slime-spore fungus, its conidia can readily be blown from the conidiophores. No spores could be induced to take off from Mucor ramarmianus even at the highest air speeds used.