Trunk rot caused by Hexagonia hydnoides

The causative agent of this disease is the wood-decay fungus Hexagonia hydnoides, which belongs to the Basidiomycota phylum. It functions as a saprotroph and a facultative parasite, primarily causing white rot. The pathogen typically gains entry into the tree through wounds, sunscald cracks, or improper pruning cuts where the inner wood is exposed to the environment.

This fungus is known to affect various tropical and subtropical tree species, with significant economic impact on mango orchards (Mangifera indica). It can thrive both on dead wood and weakened living trees, effectively utilizing the cellulose and lignin components of the wood, which leads to structural failure of the affected tree trunks.

Symptoms of the infection include the appearance of dense, hirsute to strigose sporocarps (fruiting bodies) on the surface of the bark, typically brown in color. Internally, the wood undergoes degradation, turning soft, spongy, and pale in appearance. This loss of vascular integrity prevents the tree from transporting water and nutrients efficiently from the roots to the canopy.

Environmental conditions that favor the development of Hexagonia hydnoides include high humidity and warm temperatures, which are characteristic of tropical orchards. The dissemination of spores is facilitated by wind, rainfall, and contaminated tools. Poor orchard hygiene, such as leaving pruning debris on the ground, creates a reservoir for the pathogen to spread to healthy trees.

Effective prevention and control require a comprehensive approach focusing on sanitation. Important measures include:

• Prompt removal and destruction of infected limbs or entire dead trees.
• Sterilization of pruning tools using alcohol or bleach solutions between trees.
• Application of wound dressings to large pruning cuts to prevent fungal colonization.
• Maintaining optimal tree health through balanced fertilization and stress mitigation.