Azalea gall

The disease known as azalea gall is caused by the parasitic fungus Exobasidium rhododendri. This pathogen specifically targets plants in the Rhododendron genus, including azaleas. It disrupts the normal development of leaf cells, leading to the formation of abnormal, swollen growths known as galls.

The primary symptom is the appearance of fleshy, enlarged tissues on leaves and buds. Initially, these growths may be light green or pale yellow, but they frequently turn pinkish or reddish as they mature. Eventually, the surface of these galls becomes covered with a white, powdery layer, which is the spore mass of the fungus.

Development and spread of this disease are heavily dependent on cool, moist weather conditions, especially during the spring leaf-flushing period. Rain and high humidity provide the necessary environment for the fungus to produce spores, which are then spread to healthy foliage via wind, splashing water, or garden tools, allowing the cycle to repeat.

The damage caused by azalea gall is primarily aesthetic, but severe infections can affect the overall vigor of the host plant. By diverting nutrients to the gall tissue and causing premature leaf drop, the fungus weakens the shrub's photosynthetic capacity. Over several seasons, this can lead to stunted growth and reduced blooming potential.

Management of this fungus requires an integrated approach to maintain the health of the plant:

• Manually picking and destroying galls before they turn white and release spores.
• Removing and disposing of all plant debris under the shrubs in autumn.
• Applying appropriate fungicides in early spring to protect emerging buds.
• Improving air circulation through proper pruning and planting spacing.