Dothiora ribesia

Dothiora ribesia is a fungal pathogen responsible for causing a specific bark disease in plants belonging to the Ribes genus. It belongs to the class of ascomycetes and specifically targets the cortical and woody tissues of currants and gooseberries. If left untreated, the infection can significantly weaken the plant, leading to stunted growth and branch mortality.

The host range is primarily limited to currant species (black, red, and golden) and gooseberries. The fungus often acts as a wound parasite, successfully establishing itself in plants that have already been weakened by environmental stress, frost damage, or improper pruning practices. It is a persistent issue in regions with high humidity and moderate temperatures.

Visible symptoms often appear in the early spring. Key signs of infection include:

• Dark, sunken necrotic spots appearing on the stems.
• Cracking and peeling of the bark as the infection progresses.
• The emergence of minute, black, pimple-like fruiting bodies (stromata) on the bark surface.
• Dieback of branches or individual shoots due to disruption of vascular tissue.

Development and spread of the disease are highly dependent on moisture levels. Spores are primarily dispersed through rain splashes and wind, which transport the inoculum from infected parts to healthy tissue. Once the spores land on a suitable site, such as a pruning wound or a natural crack in the bark, the fungus penetrates the host tissues and initiates the colonization process.

Effective management requires a combination of sanitation and chemical prevention. Growers must practice regular pruning, specifically removing and destroying all infected branches to reduce the inoculum load. Applying copper-based fungicides during the dormant period is a standard practice to prevent early infections. Proper spacing and airflow within the canopy are also essential to minimize the humidity levels conducive to fungal growth.