Impact of Pathogenic Fungi on Leaf Surface Wettability: A Case Study of <i>Erysiphe castaneigena</i>

Leaf surface wettability significantly influences rainfall interception and the overall water balance within forest ecosystems. However, the effects of biological factors, particularly fungi, on this critical property have not been extensively documented. In this study, we assessed the impact of Erysiphe castaneigena, a powdery mildew fungus, on the wettability of leaves from Japanese chestnut trees. We compared the wettability of infected and uninfected leaves by measuring the contact angles of water droplets on their surfaces. Our analysis revealed that leaves infected with the powdery mildew fungus displayed significantly higher hydrophobicity compared with uninfected leaves. This increased hydrophobicity correlated with the densification of the mycelium as the fungal coverage of the leaf surface expanded. These findings emphasize the substantial influence of phyllosphere microorganisms such as powdery mildew fungi on leaf wettability. Our results also enhance our understanding of the ecohydrological implications of microbial interactions on leaf surfaces, highlighting the need for further research into how these processes impact broader ecological and hydrological systems.