Chrysoporthe canker of eucalyptus

Chrysoporthe austroafricana is a highly destructive fungal pathogen known for causing stem canker disease in eucalyptus plantations. This fungus has emerged as a significant threat to forestry, particularly in parts of Africa and Southeast Asia where susceptible species are cultivated on a large industrial scale.

The primary hosts for this pathogen are various species of the genus Eucalyptus. The fungus acts as a wound parasite, meaning it predominantly infects trees through bark damage, pruning scars, or natural fissures. Once inside the host, it colonizes the vascular tissues, effectively disrupting the plant's nutrient transport system.

Symptoms of the infection typically manifest as distinct sunken cankers on the main stems or branches. A common diagnostic sign is the profuse flow of kino (eucalyptus resin) from the affected areas. Over time, the bark necrosis becomes more extensive, often leading to the formation of callus tissue as the tree attempts to compartmentalize the infection, though this is frequently ineffective against the aggressive fungus.

Environmental conditions play a critical role in disease propagation. High humidity and moderate temperatures are ideal for the production of conidia, which serve as the primary inoculum. These spores are disseminated mainly by rain splash, wind currents, and insect vectors that visit the wounded bark, facilitating the spread of the pathogen across the plantation.

The impact of Chrysoporthe austroafricana is severe, resulting in reduced timber yield, dieback of the tree crown, and, in severe cases, the death of young trees. This poses a major economic risk for timber producers and necessitates integrated management strategies to protect forest resources.

Key management and prevention strategies include:

• Screening and selecting eucalyptus genotypes that exhibit natural resistance or tolerance to the pathogen.
• Minimizing physical damage to trees during routine silvicultural operations such as pruning or thinning.
• Strict sanitation practices, including the prompt removal and destruction of severely infected trees to lower the inoculum pressure.
• Monitoring plantation health to detect early symptoms and applying site management techniques that reduce tree stress.