Fusicoccum canker

Taxonomy and nature of the pathogen: Fusicoccum aesculi (teleomorph: Botryosphaeria dothidea) is a fungus belonging to the Ascomycota division. It functions as a opportunistic pathogen, often latent in tree tissues until environmental or physical stress triggers active development and disease progression.

Diseases and host plants: The pathogen is primarily associated with the canker disease of horse chestnut (Aesculus hippocastanum). However, it is a polyphagous fungus that can affect a wide range of woody hosts, including various ornamental trees, shrubs, and fruit trees, leading to shoot blight, limb cankers, and systemic tree decline.

Biology and lifecycle: The fungus colonizes the bark, cambium, and phloem. Spores are produced in pycnidia, small fruiting bodies appearing on the surface of infected wood. These spores are disseminated primarily by splashing rain and air currents, infecting the host through wounds, pruning cuts, or natural fissures in the bark.

Environmental conditions and impact: Disease severity is strongly correlated with host stress factors, such as extreme drought, heat, soil compaction, or concurrent insect infestations. The fungus spreads rapidly in humid environments, causing significant damage that results in girdling of branches, crown dieback, and eventually the death of the entire host tree.

Management and control measures: Controlling Fusicoccum aesculi requires integrated plant management strategies:

• Rigorous pruning and removal of infected branches to lower inoculum pressure.
• Proper sterilization of pruning tools to prevent cross-contamination.
• Improving tree vigor through proper fertilization, mulching, and irrigation.
• Application of protective fungicides during dormant periods or after severe weather events.