Powdery mildew of acacia

Pathogen and disease type: The fungus Erysiphe baeumleri is an obligate parasite responsible for powdery mildew on various host plants, primarily within the Fabaceae family. This pathogen develops superficially on the epidermis of leaves and succulent shoots, disrupting the plant's physiological balance.

Host plants: The primary host for this fungus is Robinia pseudoacacia (black locust). The disease significantly affects both young saplings in nurseries and mature trees in urban or forest environments, leading to reduced vitality and aesthetic depreciation.

Symptoms and signs: The characteristic symptom is a white, mycelial growth on the surface of the leaves, resembling a dusting of flour. As the infection progresses, the fungal mat becomes denser, leading to leaf chlorosis, curling, necrotic spotting, and early leaf drop during the active growing season.

Development conditions: Erysiphe baeumleri thrives in environments characterized by high humidity and moderate temperatures. Wind-dispersed conidia facilitate rapid spread among susceptible plants, making the disease highly infectious during the peak summer months when weather conditions are most favorable for sporulation.

Protection and control measures: Effective management relies on an integrated approach. Cultural practices include pruning and disposing of infected branches to reduce inoculum sources. In severe outbreaks, the application of chemical fungicides—specifically those containing sulfur or systemic triazoles—is recommended to inhibit mycelial growth and protect new healthy foliage.