Kramer-Collins volumetric spore samplers were used to measure concentrations ofPuccinia graminis, P. recondita, Erysiphe graminis, Cladosporium, andAlternariaspores and fungal hyphal fragments within the canopy and at 1, 3, 6 and 14 m above ground level over wheat fields near Manhattan, Kansas, USA. The largest numbers of spores of each of the named fungi and hyphal fragments were trapped during hours when free moisture was not present on host leaf surfaces. As wind velocity increased, the number of spores and hyphal fragments trapped at all heights increased. Airspora trapped at the various sampling heights under all combinations of biometeorological conditions were calculated as ratios. Location and severity of infection or frequency of occurrence of the parent fungi greatly affected the percentage of propagules released in the canopy and escaped into the atmosphere. Less than 40 ofP. reconditaurediniospores released from tillering plants in the fall and trapped at 20#x2013;25 cm were trapped at 1 m, while only 6 of those trapped at 10 cm were trapped at 1 m. Ratios for the average number of spores trapped at 3 m: 1 m during the entire sampling period were similar forP. recondita(0.54),Alternaria(0.57), andE. graminis(0.48). However, the higher ratios that occurred with spores ofP. graminis(0.72) andCladosporium(0.76), and hyphal fragments (0.77) indicate considerable mixing of locally released airspora with airspora from exogenous sources.
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