Coral spot fungus

Nectria cinnabarina, commonly known as the coral spot fungus, is a fungal pathogen that belongs to the class Sordariomycetes. It acts primarily as a weak parasite or saprophyte, colonizing dead or stressed woody plant tissues. It is a cosmopolitan species, frequently found on a wide array of deciduous trees and shrubs, such as maples, apples, lime trees, and various ornamental species.

The primary symptom of the infection is the development of distinct, bright pink to orange-red pustules on the bark, which represent the fungus's sporulating structures. As the mycelium spreads through the cortex and cambium, it causes localized necrosis (dieback). If the fungus girdles a branch, the parts distal to the infection site will wither and die, leading to significant structural damage to the tree.

The life cycle of Nectria cinnabarina involves both asexual (conidia) and sexual (ascospores) stages. The fungus overwinters in the form of mycelium within the infected bark. During favorable conditions, especially in spring and autumn, spores are released and disseminated by wind, rain splashes, and insects. These spores easily gain entry into the host through pruning wounds, frost cracks, or broken branches.

Environmental conditions play a pivotal role in the spread of the pathogen. High humidity and mild temperatures significantly accelerate the production of spores and the colonization of host tissue. Trees suffering from environmental stress, such as drought, poor soil fertility, or lack of proper pruning, are far more susceptible to successful colonization by the fungus compared to healthy, vigorous plants.

Management and control strategies focus on sanitation and preventative care:

• Prune and destroy all infected branches, cutting back into healthy wood to ensure complete removal.
• Sterilize all pruning tools to prevent the accidental spread of fungal spores between trees.
• Apply protective wound dressings or sealants to large pruning cuts.
• Maintain tree vigor through proper watering, fertilization, and site management to avoid physiological stress.
• Use copper-based fungicidal sprays during dormant periods if the orchard has a high history of infection.