Dendrobium spectabile black spots

[ksriramkumar]

Last image certainly looks like a sun burn.

[cojack2006]

Yes, I agree with the last image. Not sure what happened there. It was already damaged on that leaf when I got the plant...it was a "bag baby" from a Lowe's. The other pictures are from new growths that it has put out. The underside of the leaves that have the yellow spots are actually lesions or holes in the bottom of the leaf making the spots show up on the top side. Could this be some sort of sap eating insect? I recently applied a product called Fungicide 3 made by Garden Safe. It is a fungicide, insecticide, and mite-icide all in one. Can't remember where, but I saw this on another forum that stated copper based fungicide should not be used on dendrobiums. Hopefully it does the trick and stops whatever it is that is invading my alien orchid.

This plant has been growing in full sun on the porch in Louisiana for the last several months and keeps putting out new roots and new growth, so I guess it is happy where I have it. Not quite blooming size, maybe 4 to 5 years old and has about 10 canes that approach 8-10 inches tall. Hopefully in the next few years it will be blooming size!

[ksriramkumar]

holes in the bottom of the leaf showing up in the top could be a mite. Yes copper based fungicide is a big no for dendrobiums and softer leaf genus like stanhopea. Keep a close watch on the new leaves for the symptoms of leaf damage and yes it is a bit a slow grower.

[Catt Mandu]

Black spots are a fungal problem. Google the St. Augustine Orchid Society website, they have good information on orchid diseases and treatments. Specific fungal diseases require specific treatments, & the St. Aug website includes 2 tables with treatments for (1) orchid diseases and (2) orchid pests.

The yellow spots do look like sunburn.
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