Microscopic fungi and other contaminants on airborne pollen grains of ragweed (Ambrosia artemisiifolia L.)

Fungal particles were observed on the pollen grains of ragweed (Ambrosia artemisiifolia L.) in air samples collected in Nyíregyháza, Hungary. Microscopical observations showed the colonization of pollen grains by different fungal taxa. Concentration data were correlated with meteorological factors, day of the year (DOY), PM₁₀, PM_2.5, and spore levels. Pollen grains infected by fungi became common at the end of the pollen season. These particles correlated positively with wind speed and airborne spores, but a negative correlation was found with temperature. Pollen grains were most frequently infected with Cladosporium spp., but other fungi, such as Alternaria, Aspergillus/Penicillium, and yeasts were also found. A source of infected pollen grains was proven to be the plants’ surface, where fungi colonized pollen grains, and subsequently, they were aerosolized by wind. Our results indicate that reaerosolization events can be identified by the closer examination of fungi found on pollen grains.