Exobasidium perenne

Exobasidium perenne is a specialized phytopathogenic fungus belonging to the order Exobasidiales. It is known primarily as a pathogen affecting wild and cultivated plants of the Ericaceae family, particularly those within the Vaccinium genus, such as lingonberry and blueberry. It causes localized hypertrophy and systemic infections that lead to significant plant damage.

The disease caused by this pathogen is characterized by the formation of galls, leaf reddening, and abnormal tissue thickening. During the sporulation phase, a distinctive white to pinkish bloom appears on the undersides of leaves or on affected shoots, which consists of masses of basidiospores ready for dissemination to healthy plant parts.

The biology of Exobasidium perenne is marked by its perennial nature within the host tissue. The fungus survives the winter season as mycelium inside the stems of the host plant. This allows the pathogen to remain latent during cold periods and resume its pathogenic activity as soon as environmental conditions favor spring growth.

Environmental factors play a crucial role in the infection cycle. High relative humidity, persistent dew, and cool to mild temperatures are ideal for spore production and successful germination. The fungus spreads via wind and splashing rain, which carry spores to new growth, leading to recurring infections throughout the growing season in favorable climates.

Effective control measures require a multifaceted approach to limit the impact of the pathogen on berry yield. Primary methods include:

• Sanitation: pruning and destroying infected plant parts early in the season.
• Spacing: maintaining adequate plant density to improve air circulation and reduce humidity.
• Monitoring: early detection of leaf discoloration and swelling.
• Chemical management: applying appropriate fungicides during the pre-sporulation stage when necessary.