Honey fungus

Honey fungus (Latin Armillaria mellea) is a dangerous fungal phytopathogen belonging to the kingdom Fungi, genus Armillaria. This basidiomycete is a facultative parasite capable of switching from a saprotrophic lifestyle on dead wood to an aggressive parasitic behavior on living plants, causing white rot of roots and wood.

This pathogen affects a wide range of plants, including fruit, berry, ornamental, and forest trees. The disease it causes is widely known as honey fungus root rot. The fungus penetrates the root system, gradually advancing toward the root collar, leading to branch dieback, leaf yellowing, and eventually the total collapse and death of the host plant.

The biology of the fungus is characterized by the formation of rhizomorphs — black, cord-like strands of mycelium that spread through the soil and facilitate the infection of healthy roots upon contact. The life cycle includes a vegetative stage (mycelium and rhizomorphs) and a reproductive stage, where clusters of characteristic mushrooms appear on infested wood. The fungus can persist in soil and stumps for decades.

The development of Armillaria mellea is favored by high soil moisture, tree stress caused by adverse weather conditions, pest infestations, or mechanical injuries. The fungus spreads most actively in heavy, poorly aerated soils where waterlogging occurs, as well as in plantings where stumps — the primary reservoirs of infection — are not removed in a timely manner.

The damage caused by the fungus involves the rapid death of the cambium and the destruction of root conductive tissues, rendering the plant non-viable within one to three seasons. Control measures require a comprehensive approach: removing diseased trees including their roots, stump extraction, digging isolation trenches around infected areas, applying Trichoderma-based biofungicides, and maintaining optimal horticultural practices to improve plant immunity.