Cyttariales

Cyttariales is an order of ascomycetous fungi that are highly specialized parasites of trees within the genus Nothofagus (Southern beech). These fungi are distinct due to their complex fruiting bodies and their specific evolutionary relationship with their host trees in the Southern Hemisphere.

The disease is caused by fungi belonging to the family Cyttariaceae. It is characterized as a gall-forming disease where the fungus induces abnormal tissue growth in the host. The pathogen infects living branches, altering the host's hormonal balance and resulting in significant structural damage to the woody tissues.

The primary hosts are species of Nothofagus. While these trees are adapted to their native environments, infection by Cyttariales can significantly affect their health, especially when localized in dense forests where transmission rates are naturally higher due to proximity.

The most visible symptom of the infection is the development of distinct, often honeycombed, globular stromata (fruiting bodies) that emerge through the tree's bark. These structures are often large and can cause significant swelling or distortion of the branch, eventually leading to the necrosis of the affected tissue and branch mortality.

Development and spread are facilitated by cool, temperate, and moist climates, which favor the production and release of fungal spores. Spore dispersal is primarily achieved through wind and rain, which transport the pathogens to healthy tissues on neighboring trees. Management strategies currently focus on forest hygiene, including the monitoring of tree health and the removal of heavily infested branches to reduce the overall inoculum levels in the ecosystem.