Why does your Rhododendron arboreum have white powder? Diagnose the cause and fix it with our step-by-step guide.
This fungal disease is the most common cause of white, flour-like patches on Rhododendron leaves, especially in humid conditions with poor airflow. The fungus siphons nutrients from the leaf cells, which can lead to leaf distortion and premature leaf drop.
These small, soft-bodied insects secrete a white, waxy, cottony substance to protect themselves while feeding on the sap of the Rhododendron. Colonies often cluster around leaf axils and new growth.
Certain species of scale can appear as small, white, or light-colored bumps on the stems and leaf petioles of Rhododendron arboreum. While often harder, they can present a dusty or powdery appearance from a distance.
If hard water or nutrient-heavy spray is used on the foliage, dried minerals can leave a white, powdery residue on the leaf surface. This is not a biological pathogen but an environmental buildup.
Your plant might also be experiencing one of these issues:
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