Hyphoderma praetermissum

Hyphoderma praetermissum is a species of crust fungus in the family Hyphodermataceae. As a wood-decaying organism, it is primarily recognized for causing white rot in woody plant tissues. By degrading lignin and cellulose, the fungus compromises the structural integrity of its hosts, acting as a pathogen that targets weakened or injured trees in orchards, forests, and landscape plantings.

The host range is broad, affecting both broad-leaved trees and conifers. The fungus is particularly opportunistic, seeking entry points such as pruning wounds, frost cracks, sunscalds, or damage caused by pests. Once inside the woody tissue, it colonizes the xylem, gradually spreading throughout the plant's internal structure and reducing its overall vigor over several years.

Key symptoms include the appearance of thin, resupinate (crust-like) basidiocarps on the surface of the bark or deadwood. These fruiting bodies are typically white to creamy-white and have a granular or finely warted texture. Internally, the wood becomes discolored, bleached, and soft. Advanced stages of infection are characterized by a brittle, stringy texture that significantly increases the risk of limb breakage or tree failure.

The development and spread of Hyphoderma praetermissum are heavily dependent on moisture. The fungus thrives in humid, shaded environments where air circulation is restricted. Basidiospores, produced by the fruiting bodies, are dispersed by wind and splashing rain, allowing the pathogen to travel to new host sites, especially during rainy seasons when surfaces remain moist for extended periods.

Management strategies for this fungus focus on sanitation and preventative care to protect woody plants:

• Maintain tree health through proper fertilization and watering to improve natural defenses.
• Apply pruning best practices, making clean cuts and avoiding damage to the branch collar.
• Use protective wound dressings or copper-based fungicides on major cuts or injuries.
• Prune and remove infected or dead wood immediately to reduce the reservoir of fungal spores in the environment.