Diatrype stigma

Diatrype stigma is a species of ascomycete fungus that functions primarily as a saprotroph, though it can act as a weak opportunistic parasite on weakened woody plants. It belongs to the Diatrypaceae family and is commonly found on various dead or stressed deciduous trees across temperate regions.

The primary hosts of this fungus include species such as birch, beech, hornbeam, and alder. The fungus typically colonizes trees that have been compromised by environmental stress, such as severe droughts, frost damage, or physical injuries to the bark caused by heavy machinery or pests.

The symptoms of the infection are characterized by the development of thin, flat stromata that erupt through the tree bark. As these structures emerge, they tear the bark, creating a distinctive rough, black, or crusty texture that resembles a stamp or brand, which is how the species earned its common descriptor.

The development of the fungus is highly dependent on humidity and temperature. Spores are released in moist conditions and disseminated via wind or rain splash. Once they reach a wound or a cracked section of the bark, the fungus begins to colonize the inner tissues, eventually leading to localized necrosis of the cambium.

While often considered a secondary pathogen, its presence indicates poor tree health and can accelerate the decay of branches, ultimately shortening the lifespan of the host. Prevention focuses on integrated forest health management: maintaining tree vigor through proper irrigation, preventing mechanical bark damage, and conducting timely removal of infected debris to limit the buildup of inoculum.