Dendrobium Leaves Turning White In Center

Question

at first I thought the white center area of my dendrobium were from sunburn. But many of the affected area are on leaves that don’t get touched by sun (this plant lives on a lanai in Sarasota, FL). And the white area continues to expand and spread to other farther away leaves, especially new ones. I thought maybe mites so I wiped the leaves and sprayed them with water. No luck in stopping this. Then I thought maybe this is a type of fungus so I sprayed the plant thoroughly with Dithane 45. Later with a copper fungicide. I could not tell if the problem had stopped spreading so I removed all the affected leaves and moved the plant back farther from any sunlight through the lanai screens. What is your diagnosis? Many thanks!

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Answer 1

It doesn't look like powdery mildew and you say it is not in the sun. Another possibility is overwatering, especially if the container is too large. They like their roots to be crowded. Also try using distilled water if you are using tap water.

https://www.gardeningknowhow.com/ornamental/flowers/orchids/dendrobium-orchid-info.htm