Leaf and flower gall

Leaf and flower gall is a fungal disease caused by the Exobasidium genus. This pathogen is a biotrophic fungus that targets specific tissues of plants in the Ericaceae family, causing abnormal cell growth and the development of distinct gall-like structures.

The primary hosts for this disease are species of Azalea and Rhododendron. The infection is most prevalent during the cool, wet conditions of early spring, which coincides with the emergence of young, susceptible leaf and flower buds.

Symptoms of the disease are easily recognizable: affected leaves or flowers thicken and swell, often turning from a pale green to a reddish or pinkish color. Eventually, these galls become covered with a white, powdery fungal bloom, which is composed of spores waiting to be dispersed to new hosts.

The disease thrives in high humidity and damp conditions. The spores are typically spread through splash dispersal during rain or overhead irrigation, and they can also be carried by wind. Poor air circulation within the shrub canopy provides an ideal microclimate for the fungus to establish itself.

Control measures rely heavily on sanitation and cultural practices. Gardeners should manually remove and destroy any visible galls before they release spores. To prevent recurrence, it is essential to minimize overhead watering, thin out the plants to improve airflow, and apply appropriate fungicides during the early leaf-out stage if the infection is persistent.