Dime canker

Dime canker, caused by the fungus Durandiella pseudotsugae, is a specific bark disease primarily affecting Douglas Fir (Pseudotsuga menziesii). This pathogen acts as a localized parasite, invading the cortical tissues and damaging the tree's vascular system, which can result in significant branch dieback.

The causal agent, Durandiella pseudotsugae, is an ascomycete fungus that thrives by infecting healthy trees through bark fissures, frost cracks, or wounds caused by external mechanical injury. Once established, the fungus colonizes the inner bark and cambium layer, causing necrosis and preventing the normal transport of nutrients, which effectively starves the distal parts of the tree.

The disease is characterized by the formation of small, sunken, coin-shaped lesions (cankers) on the bark of twigs and small branches, which gives the disease its common name.

• Common symptoms include:
• Localized resin flow (gummosis) around the canker.
• Browning or yellowing of the foliage on affected branches.
• Premature needle cast.
• Branch girdling and eventual death of the affected part.

The development and dispersal of the fungus are heavily influenced by environmental conditions, particularly cool and humid weather. High humidity facilitates the production and spread of fungal spores. Furthermore, trees growing in overcrowded stands with poor air circulation are more susceptible to infection, as are those stressed by drought, poor soil quality, or physical trauma.

Management of Dime canker relies heavily on sanitation and cultural practices. It is crucial to monitor plantations for signs of infection and remove and destroy any symptomatic branches or small trees to reduce the inoculum load. Maintaining tree vigor through proper fertilization, avoiding site stress, and ensuring sufficient spacing between trees can significantly decrease the likelihood of an outbreak.