Oncidium: desperate measures for a desperate situation
Following the advice I had on this forum, today I have repotted the Oncidium into a much smaller pot. The roots are in bad condition. I sprayed them with a fungicide.
The pot is a sort of "yogurt" pot (faisselle) with apertures on the side and holes in the bottom. I cut another pot and put it upside down full of clay beads.
You can see a new growth in one of the pictures.
I am spraying the surface every day.
Any more advice?
I would really like to save it.
It should recover since it has a new growth. The trick to growing these is to set it up so that the medium dries quickly after watering and to have good air circulation around the roots. I just rooted a piece in sphagnum moss (shallow layer) and I have others growing in red lava rock or red lava rock on the bottom/sphagnum moss on top (all in basket pots). Good luck!
The fact that you have a new growth is a hopeful sign.
Try to keep it "seedling moist" ie damp but not soggy. Oncidiums are pretty forgiving. When you start to see roots form at the base of the new bulb, consider adding a little more moisture retentive media I keep mine in a mix of bark, small perlite and gravel.