Lagerstroemia powdery mildew

Erysiphe lagerstroemiae is a specialized fungal pathogen responsible for powdery mildew on crape myrtle (Lagerstroemia). This ascomycete fungus creates an external mycelial network that covers the leaf surface, severely hindering the plant's ability to thrive.

The host range is primarily limited to species of the Lagerstroemia genus. The disease is particularly damaging in nurseries and landscape plantings where it can reduce the vigor of young plants and lead to disfigurement of the ornamental canopy.

Early symptoms include small, white, circular spots that eventually coalesce to cover entire leaves. As the infection progresses, affected foliage may turn brittle, curl, and drop prematurely, while flower buds may fail to open or become deformed.

The development of the fungus is favored by warm days, cool nights, and high humidity levels. Poor airflow and crowding are major contributors to the spread of Erysiphe lagerstroemiae, making cultural practices vital for managing the disease environment.

• Select mildew-resistant crape myrtle cultivars.
• Prune plants to ensure adequate air circulation and light penetration.
• Water at the base of the plant to avoid keeping foliage wet for long periods.
• Apply preventive or curative fungicides, such as potassium bicarbonate, sulfur, or systemic triazoles, according to local agricultural guidelines.