Polypore fungi

Polypore fungi (family Polyporaceae) are wood-decaying organisms that cause severe internal damage to the trunks and branches of trees. They act as pathogens, breaking down complex organic compounds like lignin and cellulose, which ultimately leads to the structural collapse of the host plant.

These fungi primarily target woody species, with fruit trees like apples, pears, and stone fruits being particularly susceptible. Infection usually begins when fungal spores enter through wounds, cracks in the bark, sunscalds, or improper pruning cuts where the tissue remains exposed to moisture and pathogens.

The primary clinical signs of a polypore infection are the woody, bracket-like, or hoof-shaped fruiting bodies protruding from the bark. Additional symptoms include:

• darkening or softening of the wood tissue;
• reduced crown vigor and leaf chlorosis;
• premature breakage of heavy, infected limbs;
• visible internal decay upon examining hollows or knots.

Environmental conditions such as high humidity and cool temperatures favor the growth of these fungi. Once established, the mycelium spreads throughout the heartwood or sapwood. The spread is facilitated by wind-borne spores, which can travel long distances to land on nearby trees, creating a risk for entire orchard blocks.

The harmfulness of Polyporaceae is significant, often leading to the irreversible death of the tree. Management relies on strictly preventative practices: avoid causing unnecessary wounds, maintain optimal tree health through proper fertilization, and sanitize tools regularly. If an infection is found, the affected area must be excised down to healthy wood, disinfected, and sealed to prevent further decay.