Hypsostroma

Hypsostroma is a genus of ascomycetous fungi recognized as a pathogen responsible for specific bark and wood diseases in various woody plants. These fungi primarily attack the cambium layer and the cortical tissues, leading to localized necrosis and compromising the structural and physiological integrity of the affected host plant.

The host range of this pathogen includes a variety of deciduous trees and ornamental shrubs. Infection typically occurs through physical wounds, pruning cuts, or frost cracks, where the fungal spores can easily gain access to the interior tissues. Once established, the fungus begins a process of colonization that interferes with the plant’s nutrient transport systems.

Symptoms of Hypsostroma infection manifest as distorted, sunken, or blackened areas on the bark. The most distinct sign is the presence of stroma—dense fungal clusters—that erupt through the outer layer of the bark. These appear as small black bumps or pustules scattered along the infected stem, signifying the fungal reproductive stage and the potential for further dispersal.

The development and spread of the disease are highly dependent on environmental conditions. High humidity levels and moderate temperatures significantly accelerate the growth of the mycelium and the production of new spores. Furthermore, the tree’s physiological state plays a crucial role; stressed, nutrient-deficient, or poorly maintained trees are significantly more susceptible to successful colonization by the fungus.

Effective control strategies require a rigorous sanitation program. This involves the prompt removal and destruction of all infected wood to prevent spore dissemination. Preventive measures include regular sterilization of pruning tools, the application of protective wound sealants to major cuts, and ensuring overall tree health through proper fertilization and irrigation, which strengthens the tree’s innate defenses against fungal invaders.