Why does your Rhododendron viscosum have white cottony spots? Diagnose the cause and fix it with our step-by-step guide.
These small insects secrete a white, waxy, cotton-like substance to protect themselves while feeding on the sap of the Swamp Azalea. They often cluster in the leaf axils or under the foliage where moisture levels are higher.
Similar to mealybugs, woolly aphids produce a white, fluffy wax covering that can make the stems and new growth of the Rhododendron appear coated in cotton. They thrive in the humid microclimates often found around swamp-dwelling plants.
Certain species of scale insects produce a white, flocculent coating that mimics cotton. As they colonize the plant, they can cause stunted growth and yellowing of the Swamp Azalea leaves.
While the mold itself is black, it often grows on the 'honeydew' left behind by sap-sucking insects. This can create a messy, textured appearance that may look like white/greyish debris before turning dark.
Your plant might also be experiencing one of these issues:
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