Thelephora terrestris

Thelephora terrestris is a basidiomycete fungus commonly known as the earth fan or fringed earth fan. While it is often considered a saprotroph that decomposes organic matter, it can act as a significant pathogen in forest nurseries, particularly affecting the health and survival of young conifer seedlings.

The host range of this fungus primarily includes various species of conifers, such as Pinus, Picea, and Larix. It is frequently observed in nurseries where young plants are grown in dense beds, providing the necessary moisture and organic substrate for the fungus to thrive and establish its colonies.

The primary symptom of infection is the formation of leathery, brown fruiting bodies that can grow directly over the root collar of the seedling. This structure physically binds the stem to the soil surface, impeding stem development, limiting gas exchange, and potentially leading to the death of the seedling due to asphyxiation or secondary fungal pathogens.

The development and spread of Thelephora terrestris are strongly correlated with environmental factors such as high humidity, poor soil drainage, and significant accumulation of organic debris. The spores are primarily dispersed via wind and rain splash, allowing the fungus to colonize adjacent areas within a nursery rapidly if conditions remain stagnant.

• Maintain proper irrigation levels to avoid soil surface saturation.
• Ensure adequate spacing between seedlings to promote air circulation.
• Remove weeds and organic debris from the nursery beds regularly.
• Apply registered fungicides during peak humidity periods if an outbreak occurs.
• Use sterilized growing media to minimize initial inoculum levels.

Effective management relies on a combination of cultural practices that disrupt the fungus's lifecycle. By maintaining dry soil surfaces and minimizing organic matter accumulation, nursery managers can significantly reduce the risk of infection and ensure the production of healthy, high-quality conifer planting stock.