The online version contains supplementary material available at 10.1007/s10453-026-09909-w.

Abstract Ambrosia artemisiifolia L. (common ragweed) is an invasive species in Europe that produces highly allergenic pollen with substantial health impacts. Recently, populations showing aberrant floral morphotypes, characterised by bracteate racemes and strongly reduced or absent staminate heads, have been observed, particularly at field margins. The causes of these abnormalities remain unclear, although the involvement of pathogens has been suggested. We hypothesised that aberrant populations differ from typical ones in both the amount of airborne pollen released and the spectrum of other bioparticles, including potential phytopathogens. To test this, spore traps were installed at three heights (0, 50, and 150 cm) above both typical and aberrant populations, and the captured airborne bioparticles were analysed. Pollen concentrations were markedly reduced above aberrant populations, consistent with their feminised floral structures. Differences were also observed in the composition and abundance of airborne fungal spores, with several phytopathogenic taxa, such as Cryptophyllachora, Albugo, and Puccinia, occurring more frequently above aberrant stands. These findings provide the first aerobiological evidence of distinct airborne particle profiles associated with the aberrant morphotype, highlighting possible links with phytopathogens. Further work, including tissue-level pathogen detection, will be required to confirm causal relationships.

Abstract Influenza seasonality is influenced by environmental and ecological conditions as well as evolutionary processes shaping the transmission potential of airborne Influenza A virus (IAV) particles and subsequent infectious disease. Considering fluctuating environmental conditions with absolute humidity as a key driver, we analyzed environmental effects on the infection dynamic in Germany during the influenza seasons between 2010 and 2018. Despite the fact that Germany is a comparably homogenous country with regard to socio-economical, and environmental properties, influenza seasons differed significantly between individual German counties and cities, with a clear gradient in incidence and intensity between the Southeast and Northwest. Thus, the transmission of IAV influenced by slight differences in the predominant weather conditions throughout Germany, emphasizing the importance of air temperature and absolute humidity for airborne flu virus transmission.

Abstract The allergenic nature of ash (Fraxinus sp.), an important element of the dehesas, has been poorly studied in meridional Europe owing to the low concentrations of this pollen type in the atmosphere. However, it has cross-reactivity with Olea L. and other homologous allergens of trees and herbaceous species, leading to earlier and more prolonged respiratory allergenic symptoms. The main aims of this work were to characterize the main pollen season (MPS) of ash from 2011 to 2022, to evaluate the influence of meteorological variables on airborne concentrations of this pollen type and to elaborate a pollen calendar for Fraxinus in Salamanca. The aeropalynological analysis for the eleven years of the study shows that the MPS for Fraxinus begins on 27 th December until 4 th April with an average duration of 100 days, a mean peak value of 57 grains/m3 reached on 22 nd February and a mean annual pollen integral of 567 grains/m3, observing an earlier onset of MPS, an increase in its duration and a decrease in its concentrations, presumably linked to climate change. Regarding the influence of meteorological parameters on pollen concentrations, positive correlations were found for maximum and mean temperatures and insolation, as well as southeast winds and frequency of calms, while negative correlations were reported for precipitation, relative humidity, and wind speed. The analyze of Fraxinus pollen could be used to predict seasonal behavior and warn people who may suffer pollinosis either from ash pollen or from cross-reactivity events.