A well-documented case of honey fungus (*Armillaria*) disease in North America occurred in conifer forests of the western United States, where *Armillaria solidipes* (formerly *A. ostoyae*) has caused widespread mortality of Douglas-fir and other species.** —

🌲 Case Study: Armillaria Root Disease in the Western U.S. – **Location:** Northern Idaho and the Pacific Northwest (Oregon, Washington, Idaho, Montana). – **Pathogen:** *Armillaria solidipes*, one of the most damaging root pathogens in North America. – **Impact:** – In Douglas-fir forests, Armillaria root disease has created **large understocked openings** where infected trees die, leaving gaps in the canopy. – The fungus spreads underground through **rhizomorphs**, infecting neighboring trees and causing chronic mortality. – It is considered the **most common forest root disease in western North America**, affecting nearly all conifer species to some degree. —

🌳 Real-Life Example: Black Oak in North Carolina – **Location:** North Carolina, USA. – **Species affected:** Black oak (*Quercus velutina*). – **Pathogen:** *Armillaria solidipes*. – **Details:** A recent finding documented Armillaria root disease killing black oaks in North Carolina. Researchers noted that climate stress (heat and drought) increased susceptibility, and the disease is expected to worsen with climate change. – **Environmental consequence:** Loss of mature oaks reduces canopy cover, wildlife habitat, and forest resilience. —

⚠️ Broader Environmental Consequences in North America – **Forest productivity loss:** Armillaria root disease reduces timber yields and complicates reforestation efforts. – **Biodiversity decline:** Mortality of dominant species like Douglas-fir and oak alters forest composition. – **Climate stress interaction:** Drought and extreme weather increase tree vulnerability, making outbreaks more severe. – **Persistence:** Once established in stumps and roots, Armillaria can survive for decades, making eradication nearly impossible. —

📌 Conclusion Honey fungus (*Armillaria*) disease in North America is not just a garden issue—it is a **major forest health problem**. From Douglas-fir mortality in the Pacific Northwest to black oak decline in North Carolina, Armillaria root disease demonstrates how fungal pathogens can reshape ecosystems, reduce biodiversity, and challenge forest management.

Sources: – U.S. Forest Service Leaflet on Armillaria root disease – USDA Forest Service research on Armillaria in Douglas-fir forests – Recent case study of black oak mortality in North Carolina