Phacidium stem dieback

Phacidium stem dieback, caused by the fungus Phacidium vaccinii, is a destructive plant disease primarily affecting lingonberry (Vaccinium vitis-idaea). The pathogen acts as an ascomycete fungus that targets the stems, eventually disrupting nutrient transport and leading to tissue necrosis and plant death.

The fungus is host-specific to certain members of the Ericaceae family, with lingonberry being the most susceptible. In industrial berry farming, this disease poses a significant risk to yield, especially in regions with cool, wet climates where moisture persists on foliage and stems for extended periods.

Early symptoms include localized discoloration of the stems, followed by cracking of the bark as the underlying tissues die. As the infection progresses, the leaves above the affected area turn chlorotic and wither. Closer inspection reveals the presence of small, dark fruiting bodies (apothecia) on the stem surface, which are characteristic of the Phacidium species.

Development of the disease is heavily dependent on environmental conditions, particularly high humidity and cool temperatures during the growing season. The pathogen survives the winter in infected plant tissue or debris. Splashing rain and wind help disperse the spores to healthy parts of the plant or neighboring bushes, facilitating the spread of the infection throughout the plantation.

Management and prevention focus on reducing the inoculum pressure and improving plant vigor. Since chemical control options can be limited, sanitation remains the primary method: all diseased plant material should be pruned and removed from the site immediately. Maintaining proper plant spacing and ensuring good drainage are crucial to creating an environment less favorable for fungal growth.

• Sanitary pruning of infected branches.
• Clearing and destroying all plant debris from the field.
• Ensuring good drainage to avoid water stagnation.
• Applying preventive fungicides during high-humidity seasons.