I have a small dendrobium antennatum in a 6 inch clay pot. It is growing
well and looks healthy by all observations. I find the leaves have a black
sooty mildew particularly on this years growth. The are no critters on them
or ever have I seen anything on this plant.

My guess is that it exudes some sort of sap that is causing this. Anyone
else see this on this lovely plant?

I've tried cleaning the leaves with a damp paper towel but it is boring slow
work. Any ideas on how to prevent this on further growth?

The only time I've seen anything resembling this is when there were scales
in the area. Not the case this time.

Good Growing,
Gene