Methods to Sample Air Borne Propagules of Aspergillus flavus

Abstract

Three techniques (cyclone samplers, filter samplers and rotorods) were evaluated for sampling airborne propagules of Aspergillus flavus in a cultivated region of southwest Arizona. Analysis of variance indicated no significant difference between cyclone and filter samplers in quantity of colony forming units caught, but there was a positive correlation between catches of the three separate impaction samplers (r = 0.84–0.99, P>0.05). There was no detectable correlation between impaction sampler catches and cyclone catches (r=0.12–0.33; P>0.05). Cyclone samplers collected a dry sample that was easy to process for quantification of fungal propagules. Size of conidia of A. flavus (combined with filter retention studies) suggests that the predominant propagules caught by the cyclone sampler were conidia, rather than sclerotia or infected vegetative matter. Using a water-soluble coating, rotorods collected viable conidia of A. flavus under controlled environment conditions, but not in the field, although viable propagules of other fungi were caught, including other Aspergilli. In the desert environment the rotorods became overloaded with particles of dust if operated for more than 2 h. Where isolate culture is required, cyclone samplers are ideal for collecting airborne A. flavus propagules in dry climates.