Megacollybia

Megacollybia is a genus of fungi that includes species often found on decaying wood. While primarily saprotrophic, in a horticultural context, it can act as a secondary pathogen, colonizing weakened trees. Its presence often indicates that the tree is already experiencing physiological stress or has damaged structural tissue.

The causal agent is a basidiomycete fungus that secretes specialized enzymes capable of decomposing wood components. It typically initiates infection through existing wounds in the bark, exposed heartwood, or compromised root systems. Once established, it acts as a white-rot pathogen, gradually degrading the tree's structural integrity.

This fungus typically attacks deciduous trees, including broad-leaved species and fruit trees in orchards. Trees suffering from environmental stress, such as severe pruning wounds, frost cracks, or insect infestations, are particularly susceptible to colonization by Megacollybia mycelium.

Diagnostic symptoms include the emergence of fungal fruiting bodies (mushrooms) at the base of the tree or on dead branches. Internally, the wood undergoes discoloration and softening. Advanced decay often leads to mechanical failure, making the affected tree hazardous during storms or high winds.

Effective protection relies on integrated management practices. Key measures include maintaining tree vigor through appropriate fertilization and water management, sanitizing all pruning tools, and immediately sealing large wounds with professional-grade wound dressings. Keeping the orchard floor clean of large woody debris is also essential to reduce local spore pressure.