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Browsing by Subject "Forest Health"

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    Investigations of Potential Plant Pathogens in Forests and Nurseries in Minnesota and Fungal Diversity studies in the Ecuadorean Amazon
    (2024-07) Rajtar, Nickolas
    Plant pathogens pose significant threats to natural ecosystems and managed landscapes, leading to substantial economic losses and ecological damage. Despite their potential impact, there remains a gap in comprehensive biosurveillance to monitor and understand the distribution and diversity of these pathogens. This dissertation addresses this gap through three biosurveillance projects focusing on detecting and describing canker fungi associated with emerald ash borer in Minnesota, the distribution and diversity of Phytophthora species across environments in Minnesota and the diversity and decay potential of Xylaria species in the Ecuadorian Amazon Rainforest. Chapter 1 investigates the pathogenicity of canker fungi associated with emerald ash borer (EAB)- infested ash trees in Minnesota. The study focuses on seven fungal species isolated from EAB galleries and tests their potential to cause cankers in white ash (Fraxinus americana). The pathogenicity of these fungi was tested using two inoculation methods, and the results demonstrated that several fungi, particularly Diplodia mutila, Cytospora pruinosa, and Diplodia seriata, cause significant canker formation. This research underscores the potential role of these fungi in exacerbating the decline of ash trees affected by EAB. Chapter 2 presents a survey of Phytophthora species in Minnesota, examining their presence across various built and natural environments including nurseries, forest stands, and waterways. This study expanded upon previous Phytophthora surveillance activities which had been limited in geographic scope, and which had predominantly sampled diseased plant material from nurseries. Over four years, soil, plant, and water samples were collected from nurseries, forest stands and urban landscapes. The survey identified 22 distinct Phytophthora species, including 14 previously unreported in Minnesota. The findings highlight the diversity of Phytophthora species in Minnesota and emphasize the need to monitor nurseries as a potential source of entry for new, and potentially hazardous, species to the state. Chapter 3 explores the diversity and decay potential of Xylaria species in the Ecuadorian Amazon Rainforest. Through extensive field collections and laboratory analyses, the study identified numerous Xylaria species, many of which (60 within a one hectare area) were previously undescribed. The decay potential of selected Xylaria species was assessed on various wood types, revealing significant biomass loss and indicating their role in nutrient cycling within the rainforest ecosystem, in particular trees that are high in extractives and regarded as being resistant to decay. This research presents critical new information on the presence and impact of plant pathogens and diverse fungi in Minnesota and the Ecuadorian Amazon. It highlights the importance of biosurveillance for understanding plant pathogens, pests, beneficial organisms and their interactions and implications for forest health and ecosystem dynamics. These findings contribute to the broader field of plant pathology and provide valuable insights for detecting, mitigating and managing the impact of plant pathogens.