Sticky sap on Dendrobium Nobile
 

I have several Yamamoto Den. Nobile hybrids that are flowering. Several have stick sap on the underside of the leaves at there base. I cannot see any infestation of bugs or brown scale, which is what usually causes sticky sap. Does anyone have an idea as to what is causing this?

Honeydew. It's a good thing. Taste it and see for yourself!

It can be normal in various orchids. Sometimes it's referred to as Happy Sap :) As long as nothing is causing it (such as bugs) then it's considered a sign the plant is happy.

Thanks for the information. Every other time I have seen sticky sap it has been because of brown scale. I have used Bonide horticultural oil to resolve infestations before. The orchids are flowering, so I don't want to spray them now.

Ya I second what the other posters have said. I have a phal. violacea that makes a ton of sap at the spike before and during the formation of buds. No idea what your plant is doing, but as long as there is no insects you're fine.

I had it all over the spikes of my B. nodosa while it was blooming, and the amount that a Poinsettia I'm trying to carry over to next year produced was incredible. I generally agree with Greenthumbz about insects, but with one exception. If you have a plant producing it outside, there will be ants! It's quite possibly why the plants produce it in the first place. A bunch of angry ants defending their food is more than most plant pests want to deal with! Just make sure there are no aphids or other pests present along with the ants.