Rotting pseudobulb on my Cycnoches cooperi
 

The most recent pseudobulb on my Cycnoches cooperi is rotting. I am planning to cut the pseudobulb above the rotted part and to separate the previous year's pseudobulb (which is still fairly firm) in the hope that one of those two will sprout a new pseudobulb. Does that approach seem reasonable to you? Do you have other suggestions?

On the cut pseudobulb, would you put anything on the wound? Cinnamon? Thiomyl?

That seems reasonable to me.
You could sprinkle cinnamon on the cut bulb. Only other thought is to perhaps spray the plant all over with a disinfectant like dilute bleach or Physan 20 before cutting. And be sure to sterilize the cutting tool as well. I'd keep it in a dryish place with good air movement until the wound has completely dried out.

I caution using cinnamon as it is also a desiccant and the pbulb holds water. I have had better results with candle wax to seal the cut. I have been getting into bonsai recently and the thought that cut paste would probably be the best option.

Seems like a good plan! I've had good results with cinnamon over the years, but the candle wax idea sure sounds interesting!

I can't really say if it was the cinnamon or just that the wound is left open, but those bulbs shriveled a lot more with cinnamon. The candle wax seals the wound and the bulbs don't lose as much water.

Maybe cinnamon, then candle wax? I have one I noticed last night was starting to rot. I'll try that this time.

I had the same thing happen to last year's bulb from a Cycnoches warscewiczii recently. I tried cutting it back to healthy tissue and covering the wound with cinnamon. 2 days later it was continuing to rot. I cut again and drenched it with a Carbendazim fungicide. seems to have stopped the rot. Hopefully it will get a new growth from one of the nodes.

Thank you all!

I've decided to give the wax idea a try. I first treated the cuts with Phyton 27, let it act for about an hour, dried the cuts and then applied the wax. I'll keep my fingers crossed that at least one of the pieces will produce a new pseudobulbs.

I'll keep you updated.

@SG in CR: Good luck with you Cycnoches warscewiczii.

Are you able to keep the pieces in a humid place?

I posted here a couple of years ago about a Catasetinae hybrid I dropped during dormancy, breaking the newest pseudobulb into three pieces. I coated each broken surface with candle wax and put them with the dormant relatives. In Spring they all began pushing new growth, rooted and were growing well. Then a rat ate them.

I have been hesitating about putting the pieces in a humid place since I don't want to encourage more rot. But I am now seeing some drying on the ends despite the wax so I decided to "sphag and bag" them and monitor closely.

@estación seca: Thank you for the encouraging words. Rats should not be an issue in my apartment...