Dermea canker

Dermea canker is a fungal disease caused by the ascomycete Dermea pseudotsugae. It is a pathogen known to cause localized necroses and cankers on the bark, cambium, and phloem of susceptible conifer species, significantly affecting their physiological state.

The primary host for this pathogen is the Douglas Fir (Pseudotsuga menziesii). While it can affect trees of various ages, it is particularly problematic in stands where trees are already stressed by environmental factors, frost, or other site-related issues.

Symptoms of the infection include the formation of distinct, sunken cankers on stems or branches. Over time, these cankers can girdle the affected woody part, leading to dieback. During moist conditions, the pathogen produces characteristic fruiting bodies on the surface of the dead bark, which release spores that facilitate further spread.

The development and dissemination of the disease are highly dependent on moisture levels. Spores are primarily dispersed by rain splash and wind, entering the tree through wounds or small bark fissures. Cold winter injuries often act as the primary entry point for the fungus, making late-winter and early-spring inspections critical.

The economic impact of Dermea canker ranges from branch mortality to the total death of young trees. Effective management involves strict forest hygiene, including the removal and destruction of infected material to reduce inoculum levels. In nurseries, managing the spacing of plants and controlling moisture levels helps minimize the conditions favorable for spore germination and infection.