Cytospora canker of eucalyptus

Cytospora canker, caused by the fungal pathogen Cytospora eucalypticola, is a destructive disease affecting the bark and cambium layers of various eucalyptus species. This fungus functions as an opportunistic parasite, exploiting compromised tissues to colonize and destroy the host's vascular system.

The host range is primarily focused on the genus Eucalyptus. The fungus often targets trees under physiological stress, such as those suffering from water deficit, nutrient deficiency, or prior damage from frost, pruning wounds, or wood-boring insects, which facilitate the entry of the mycelium.

Symptoms of the infection include localized discolored areas on the bark, the formation of sunken cankers, and longitudinal cracking of the bark surface. As the infection progresses, the fungal stroma may erupt through the bark, releasing spores that continue the cycle of infection throughout the canopy and surrounding trees.

Environmental conditions that favor the development of Cytospora eucalypticola include high humidity, moderate temperatures, and prolonged moisture on bark surfaces. Spore dispersal is typically achieved through wind currents and rain splashes, which move the pathogen from infected areas to healthy, susceptible host tissue.

The economic impact of this disease is significant, often leading to canopy dieback, stem deformation, and eventually, tree mortality. To manage this pathogen, it is essential to focus on integrated control measures, including:

• Removal and destruction of heavily infected wood.
• Sterilization of pruning tools to prevent cross-contamination.
• Minimizing tree stress through proper irrigation and site management.
• Applying protective fungicides on major pruning wounds.