Powdery Mildew on Gardenia & Plumeria: Diagnosis & Treatment

Question: White foamy, sticky stuff on potted gardenias and plumeria. Black dots on plumeria foam when scraped. What is it? Treatment?

Answer: Powdery Mildew (Fungal Disease)

Not insects. Prevalent in wet/humid conditions. The "black dots" may be fungal structures or sooty mold on honeydew from secondary insects.

Soap Shield (Gardens Alive) – organic, effective
Many copper fungicides at garden centers
Critical: Start spraying early summer preventatively; curative treatment is difficult once established

Treat now to limit spread; prevent next year with early sprays.

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