In a mature, otherwise healthy looking cattleya, two pseudo bulbs suddenly turned brown and became mushy. Note that the leaf is completely normal looking (at this point.). I would love any suggestions as to what I am dealing with.
Ed
I am not very knowledgeable in catts, however, my first thoughts are to question the roots, growing medium breakdown, or bug infestations, etc. I would wait until someone more experienced with catts comes along, but I would think you should look at the leaves to see if you have any sneaky critters eating away at it, if the roots are not drying out well, or if the potting medium is due to be changed.... good luck!
Your picture is a bit too small to see what media it is potted in. To me it looks like moss. Usually the first thing to check is roots. I rarely pot my cattleyas in moss and the only one I do have in moss is in a clay pot. The roots need air and so a chunky open mix such as bark or coco chunks are commonly used. It is watered thoroughly but then dries quickly so the roots don't rot.
It would help to know how long you have had the plant-it looks well established, and when it was last potted and your culture. Is it allowed to dry out between watering?
Obviously one pseudo bulb has been removed. I would remove the other as well if you haven't already. Make sure to remove all rotten material up to healthy green tissue. Treat the cuts with cinnamon, or hydrogen peroxide or some garden sulfur. Something to seal and disinfect the area.
noticing the bulb has bloomed I think its jus a tired old bulb thats done its job. if it was a new bulb i would worry some. and right just cut it and treat it with cinnamon and move on to the next one
If the pseudobulb is mushy it's possibly black rot or another fungal problem. Black rot is so fast that it can happen overnight. Cut the pseudobulb below the dark area, with sterilized shears. The cut should show only green healthy tissue so you know you got it all. The rot can spread to the rest of the orchid if you leave the pseudobulb in place although sometimes it doesn't spread. One way to prevent rot is to use a systemic fungicide like Thiomyl but I know many growers don't want to resort to chemicals. Good luck.