Exobasidium vaccinii-uliginosi

Systematic position and nature of the pathogen
Exobasidium vaccinii-uliginosi is a basidiomycete fungus classified within the order Exobasidiales. It acts as an obligate parasite specifically targeting plants within the Ericaceae family, most notably causing significant health issues in wild and cultivated blueberry plantations.

Diseases and affected crops
The pathogen is the primary cause of exobasidium leaf spot, commonly referred to as 'red leaf spot'. Symptoms involve dramatic deformation, swelling, and thickening of leaves and succulent shoots. Infected areas undergo color changes to shades of red or pink, often followed by a powdery white bloom representing the fungal fruiting bodies.

Biology and life cycle
The fungus reproduces via basidiospores that are dispersed by wind and rain splashes onto susceptible plant tissue. Once the spores germinate, the mycelium invades the host tissue, inducing abnormal cell hypertrophy. The pathogen overwinters within infected plant materials, allowing it to initiate new infections as soon as favorable conditions return in the spring.

Conditions for spread and economic damage
High humidity, frequent precipitation, and cool to mild temperatures are ideal for the rapid spread of this fungus. The economic impact is significant, as it leads to reduced plant vigor, defoliation of infected shoots, and a reduction in both the size and quality of the blueberry harvest, ultimately affecting the overall yield of the plantation.

Protection and control measures
Management of Exobasidium requires a proactive strategy.

• Sanitary pruning of symptomatic parts is essential to reduce the inoculum load.
• Improving air circulation through proper spacing and pruning.
• Applying protective copper-based or systemic fungicides early in the growing season.