Research

Research projects

The Phyllosphere Mycobiome of Horse Chesnut: Herbivory, Fungal Pathogen Dynamics, and Trees´ Resilience in Urban Ecosystems  

Horse chestnut (Aesculus hippocastanum) is an essential tree species that is currently facing considerable ecological pressures. This study conducted a large-scale transect across major European urban centers to reassess the long-standing assumption that a single fungal pathogen, Guignardia aesculi, predominantly causes widespread foliar necrosis (leaf blotching). Using the “tree health assessment” approach, we systematically recorded and analysed foliar symptoms across 700 individual trees growing under contrasting urban environmental conditions.

Research projects

How Host Switching and Drought Stress Empower a Latent Tip Blight Fungus in European Forests

Diplodia tip blight, caused by the ascomycete Diplodia sapinea, represents one of the most significant emerging threats to pine species in Europe, with particular impact on Scots pine (Pinus sylvestris), a species of high ecological and economic relevance. This research demonstrates that pathogenic characterization of this fungus is based on its function, with transitions between endophytic to pathogenic lifestyles determined by environmental stressors and host-related factors.

Research projects

The Urban Stem Cancer: Emerging and Host-Shifting Fungal Pathogens of Necrosis in Central European Urban Trees  

Stem cankers and necroses represent a disease complex in urban trees. The present research project addresses a significant knowledge scarcity concerning the emergence and spread of novel and expanding fungal pathogens that infect broadleaf (deciduous) tree species in Central European cities. The results indicate an intensifying phytosanitary problem in urban forests, caused by opportunistic fungi that take advantage of abiotic and biotic stressors characteristic of urban environments.  

Research projects

New fungal pathogens of Aesculus hippocastanum in Europe and the deterioration of its condition due to the correlation with Cameraria ohridella

The horse chestnut (Aesculus hippocastanum) is widespread in Europe, but is increasingly suffering from climate change. Fungal pathogens and infestation by the leaf miner moth (Cameraria ohridella) are severely affecting the trees. To investigate the effects of climate change, we conducted a study along a south-west to north-east European transect covering six countries and ten urban forest areas. Around 700 trees and 750 symptomatic leaves were examined.

Research projects

New pathogens in urban areas in Germany increase the safety risk posed by trunk and branch cancer

Urban trees are increasingly threatened by rising temperatures, drought and extreme weather events. These stress factors force trees to expend their energy on adapting to unfavourable conditions, weakening them and making them more susceptible to pest infestation and disease. At the same time, heat-loving insects and microorganisms are spreading in our regions, as they find ideal habitats in the changing climatic conditions.

Research projects

Investigation of invasive fungal pests in sequoia trees under drought stress

The giant sequoia (Sequoiadendron giganteum) is one of the most impressive tree species in the world and is also commonly found in urban areas in Germany, such as Freiburg. However, climate change is putting this majestic tree species under increasing pressure. Rising temperatures and changing precipitation patterns are leading to drought stress, which weakens the trees and makes them more susceptible to infection by invasive fungal pests.

Research projects

Investigating Fungal Diversity and Potential Pathogens in Symptomatic and Asymptomatic Giant Sequoias (Sequoiadendron giganteum)

Giant sequoias (Sequoiadendron giganteum) are among the largest and longest-lived organisms on Earth. Their resilience to emerging diseases, especially tip blight, is increasingly recognized as linked to their associated microbial communities, especially the mycobiome. This study represents one of the first systematic investigations of the mycobiome of S. giganteum to examine how fungal community composition and diversity relate to tree health and disease resistance.

Research projects

Assessing the Threat of Generalist and Specialist Fungi to Non‑Native Pine Diversity in European Cities

Urban environments are increasingly recognised as essential refugia for plant diversity, harbouring a broad range of non-native Pinus species planted for their tolerance of urban stressors. However, these geographically diverse Pinus assemblages can act as epidemiological hubs, where resident European fungal pathogens may readily expand their host range to colonise pine species. This tri-national survey, encompassing Germany, France, and Switzerland, evaluated the threat of the main fungal pathogens to 58 non-native pine species.

Research projects

The Mycobiome of European Mistletoe (Viscum album): Detection of the Emerging Pathogen Sphaeropsis visci on Coniferous Hosts

European mistletoe (Viscum album) is a hemiparasitic angiosperm that colonises a range of economically and ecologically significant tree species, including Scots pine (Pinus sylvestris). This project emphasises the parasite itself, with particular attention to the structure and function of its associated fungal communities (the mycobiome).

Research projects

Investigating Diversity and Spread of Phytophthora Species in Urban and Forest Ecosystems of Germany and Neighbouring Countries

Phytophthora is a genus of oomycetes (water moulds) that comprises some of the most destructive plant pathogens worldwide, responsible for diseases such as sudden oak death, root rot, and extensive tree mortality in both forested and urban environments. 

Research projects

FORESCALE: A Transcontinental Assessment of Host–Microbiome–Pathogen Interactions in Pine and Fir Forests Using Integrated Genomics and Remote Sensing

This project, a part of the broader FORESCALE initiative, seeks to transform current approaches to monitoring and forecasting disease outbreaks in coniferous forest ecosystems. This project focuses on pine and fir species in Germany and Canada to understand the global drivers of coniferous health.