Horse chestnut powdery mildew

The causative agent of this disease is the fungus Erysiphe flexuosa, which specifically infects the foliage and young shoots of the horse chestnut tree. As an obligate parasite, this pathogen thrives by drawing nutrients directly from the host plant's tissues, primarily affecting the leaf surfaces.

The characteristic symptoms of the infection appear as white, dusty patches of mycelium on the leaves. As the disease progresses, these patches expand and merge, causing the leaves to curl, become chlorotic, and eventually drop prematurely, significantly impacting the visual health of the trees in landscaping.

The development and spread of Erysiphe flexuosa are favored by warm, humid conditions and stagnant air within dense canopies. Conidia are spread by wind currents from tree to tree, allowing the infection to colonize large urban parks or avenues rapidly during the growing season.

The economic and aesthetic harm caused by this fungus is significant, as it severely reduces the photosynthetic capacity of the horse chestnut. Repeated annual infestations weaken the trees, making them more susceptible to drought, winter damage, and secondary pests or pathogens that further threaten tree vitality.

Effective management and prevention strategies involve several key practices:

• thorough cleanup and removal of fallen leaf litter to reduce the fungal overwintering inoculum;
• proper pruning to maintain good air circulation and light penetration throughout the crown;
• application of specialized fungicides during the early stages of the disease outbreak;
• monitoring tree health to ensure prompt intervention against initial fungal colonies.