Stictis stellata

Stictis stellata is a species of fungus in the order Ostropales that acts as a pathogen causing lesions on the bark of various woody plants. While it often functions as a saprotroph, under conditions of plant physiological stress, it behaves as a facultative parasite, colonizing the bark and cambium of weakened trees.

The host range of this pathogen includes various broad-leaved trees, particularly species of Populus (poplar), Salix (willow), and Populus tremula (aspen). It is frequently found in nurseries and managed forest stands where trees are prone to stress factors such as frost cracks, sunscald, or mechanical injury.

The primary symptom of infection is the emergence of distinctive apothecia—the fruit bodies of the fungus. These appear as small, star-shaped structures that erupt through the epidermis of the bark. These apothecia often feature a white, lobed margin surrounding a darker central disc, which is the key identification feature for this fungal disease.

The spread and development of the disease are highly dependent on environmental moisture levels. High humidity, heavy precipitation, and prolonged wet periods create an ideal environment for spore germination and colonization. Fungal spores are dispersed by rain splash and wind, effectively infecting vulnerable areas of the bark where protective layers have been compromised.

The impact of Stictis stellata on tree health manifests as tissue necrosis, leading to branch dieback and, in severe cases, the decline of the entire tree. To prevent the spread of this pathogen, it is critical to implement sanitation measures, including the pruning of infected branches and ensuring optimal tree health to increase natural resistance to infection.