What is the chalky deposit on laurel leaves?

The chalky deposit on laurel leaves is primarily caused by a fungal infection known as powdery mildew. This white, powdery substance consists of fungal spores and mycelium, which thrive in warm, dry conditions. The presence of this deposit can indicate stress in the plant, often linked to poor air circulation or high humidity. Regularly inspecting and maintaining proper growing conditions can help prevent this issue.