Catasetum bulb black spot
 

Hello everyone and Happy New Year to all the members! I'm new in this forum, I found it occasionally when I searched the web for answers about my orchids. I have been growing orchids for 5 or 6 years, mostly phalaenopsis, but I fell in love with catasetum orchids this summer. So I have FDK After Dark SVO black pearl, I was so excited that I've read a lot about the growing process and etc. Everything was fine by Christmas - I had to leave for the holidays; by then the plant had 2-3 leaves already starting to turn yellow, so I moistured the roots for the last time. Now when I came back I found my catasetum with all leaves yellow, they fell, I cut the roots, but I saw these black spots on the new bulb...they are not soft. I've read a lot in the forums and also I've got an advice to cut out the rotten parts and apply cinnamon, but since this is my first attempt with this orchid I don't want to loose it...Please, help! :)
Thank you in advance and sorry for my English :)

If it's not soft, don't worry. If it does start to soften, cut away the affected part immediately and let the rest dry out. Catasetum will regrow from large enough pieces of healthy pseudobulbs.

Thank you very much!

Not soft is definitely better than soft. If you have a systematic fungicide, such as thiomyl or a phosphorus acid fungicide - then spraying the bulb with it could be beneficial.

It doesn't look serious to me. You aren't watering it, so it isn't likely to spread. For the future, you don't have to cut the old roots. While the new roots that develop with the new growth (in a few months) are the best ones, year-old roots are still useful. Beyond that, they just die back, don't hurt anything. Now, just pot it up in some sphagnum and put it where you can totally ignore it until the new leaves have opened out and new roots are about 8 cm long before you start watering again. (The sphaghnum will be damp for you to be able to work with it, don't worry about that, it will be dry in a couple of days.

Thank you all, very much!

Looks benign at this point. No need to do anything about it.

Unfortunately the spots began to spread, so I had to cut them out...:( I think I'm going to loose it....:(

Were the spots soft?

I have encountered this before - once. I had this exact same thing develop in one of my Fdk bulbs during dormancy. Identical colouring as yours. The 3 or 4 mm diameter regions started to 'sink' after a while. I immediately decided to try my phosphorous acid based fungicide ----- sold as Yates Anti-rot phosacid here in Australia. That stopped whatever was causing the issue. The marks remained - no spreading occurred, and that bulb remains tough and healthy.

When I return home from holidays, I'll take a photograph of the treated regions and post it here. This all happened several months ago.