Black Sooty Substance on Dendrobium

Has anyone had this on their orchids? I purchased a nobile type of Dendrobium (at least thats what I think it is) a few days ago, and this morning I noticed this black sooty like substance along the canes especially on the underside of the leaf axils. I have seen this kind of substance before, but only on mangoes, never on orchids. I believe, on mangoes, they are caused by tiny insects, though I do not know exactly what they are, but they don't cause too much damage. I tried my best to clean up the black substance with cotton wool dip in fungicide solution, thinking that it might be some sort of fungus. I gave the plant a thorough inspection but couldn't see any pests or insects, but there are tiny pin marks on the underleaves where the sooty substance had been.

Any idea what this thing is? Do I need to spray the plant with insecticide? There are spikes with buds along 3 of the bigger canes and this is my first Dendrobium of this type, so I am not sure exactly what to do here. I appreciate any info, TIA.

Hi , I have seen it before on a nobile Dend. that came from Hawaii , it is from the sugary sap they produce . High humidity , warm temps. , I used diluted Physan on a cotton ball and removed it , this year none , be sure it is getting good air circulatiion , and not wet at night when the temp falls . The spores blow around and land on a prime area to grow the sugary sap on the plant . I called the place in Hawaii and they said they usually wipe it off before shipping guess they missed mine hope this helps a little . Gin

Hi Gin, thanks for the info. I did tried my best to wipe off the stuff with cotton ball soaked in fungicide but there are still some in areas I couldn't reach. I poured the rest of the solution onto the plant and I hope that would take care those I couldn't remove. Weather here at present is very ideal for fungus to grow, warm, and very high humidity, over 90%!!!

I don't know if your plant is indoors or outside , but this is what happned a few years back , my daughter made a plant hanger for me I had it in the green house , the sooty stuff showed up on a plant not a new one ,I would wipe it off and back it would come . I finally found out where it was comming from .. the macrame plant hanger the fans were picking up the spores , and blowing them around . Just thought about this . Gin

The black sooty stuff is just harmless mold growing on the honeydew the plant secreted. No worries....

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Louis J. Aszod