Dermea pseudotsugae

Dermea pseudotsugae is a fungal plant pathogen classified under the kingdom Fungi, phylum Ascomycota, order Helotiales, and genus Dermea. This fungus is specifically known as an agent responsible for bark necrosis and canker diseases primarily affecting coniferous species, with a particular focus on Douglas fir (Pseudotsuga menziesii).

The disease caused by this pathogen manifests as bark cankers on branches and stems. The fungus enters the plant through infection courts, such as frost cracks, pruning wounds, or mechanical injuries. Once inside, it colonizes the bark and cambium layers, leading to the formation of necrotic lesions that disrupt the tree's vascular system.

The biology of Dermea pseudotsugae involves the production of apothecia on the bark of infected branches. During periods of wet, cool weather, the pathogen releases ascospores which are splashed by rain or dispersed by wind onto healthy host tissue. This cycle allows the fungus to persist in forest environments and potentially lead to outbreaks during seasons with prolonged moisture.

The damage caused by this pathogen is significant, particularly in young plantations and nursery stocks. The progressive dying back of branches and the potential girdling of the stem can lead to severe tree decline or mortality, resulting in significant economic losses and reduced timber quality in managed forests.

Effective management and control strategies include:

• pruning and disposing of infected branches to remove inoculum sources;
• maintaining proper spacing to encourage air circulation;
• sanitizing pruning tools to prevent cross-contamination;
• avoiding practices that stress the trees and create entry points for infection;
• implementing regular health inspections in sensitive areas.