Floccularia

Floccularia is a genus of fungi that includes species responsible for causing severe root and butt rot in various woody plants. Acting as a necrotrophic pathogen, it invades the root system, eventually compromising the tree's structural integrity and its ability to transport nutrients and water from the soil to the canopy.

This disease primarily targets conifers and several deciduous species. The pathogen propagates through soil-borne mycelium and rhizomorphs, which act as underground transport systems, allowing the fungus to spread efficiently from infected stumps or roots to the root systems of healthy neighboring trees.

Early symptoms are often subtle and include crown thinning, needle discoloration, and reduced annual growth. As the root rot progresses, the tree exhibits rapid decline. A definitive diagnostic feature is the presence of white, fan-shaped mycelial mats under the bark near the root collar, often accompanied by the emergence of mushrooms at the base of the infected plant.

Environmental factors such as poor drainage, soil compaction, and site history play a significant role in the spread of Floccularia. High humidity and favorable temperature conditions accelerate the growth of rhizomorphs, making waterlogged areas particularly susceptible to widespread outbreaks of the disease.

Managing Floccularia requires a proactive approach centered on sanitation and environmental control. Key steps include removing infected trees along with their entire root systems to eliminate inoculum sources, ensuring adequate soil aeration, and applying chemical or biological fungicides to protect high-value specimens in the landscape.