Black pseudobulbs

[Leafmite]

I recognize this...I had it happen to me.

Try adding more Calcium. I had this happen once with many of my 'Cattleyas,' including my Brassavola, many years ago when I gave up my pond (had lilies and lotuses fertilized with a very complete fertilizer that included Calcium) as I had always watered my plants with the pond water. I switched to rainwater and orchid fertilizer and I thought the orchid fertilizer had everything my orchids needed. I lost most of my beloved Catts due to the 'Black Plague". Incidentally, the Brassavola nodosa was the first of my victims.

If your orchids are outside, you can add a little milk to your watering can until you can get Cali Magic or another Calcium supplement. The Calcium will prevent new growths from having Calcium deficiency.
In the meantime, continue to remove the infected growths and spray everything but the roots with Isopropyl alcohol twice a day or, if you can get ahold of a systemic fungicide, use that. I would start adding Calcium for any other orchids in the Cattleya family, too. This can go through a collection.

I add eggshells for the long term (they don't do much until they begin to decay) but also use a Calcium supplement in my watering can. Some growers use oyster shell...any source of Calcium that the orchid can use will work.

Good luck and I hope you can save your Brassavola!

[SouthPark]

Great suggestion too L.M.

At the middle of each month, I apply a mag-cal treatment. Again, great suggestion - just to bring up the possibility of element deficiency, along with the dehydration.

[Leafmite]

It certainly looks like what I experienced.

[Dulcinea]

I’m have Monterey Garden Phos. I fertilize with Michigan State University orchid fertilizer. I will also try calcium. I have oyster shell I use in some of my hoyas. Will that work or Should I use something else. I do t think that using the phos can hurt. What do you think! The brassavolas I’ve lost were hugs and wonderful until they started with the black rot as I call it. It sent from bulb to bulb. The only thing that has stopped it is the sulphur and I thought a drench would be much easier. I’ll gore
It now and check the mix and the roots.

[estación seca]

The sulfur might change the pH of your water to more acid and make calcium easier to absorb.

[Dulcinea]

I unpotted the two orchids this morning. Neither looked good. Rotten roots. I’m attaching photos in two groups . First are the named orchid. Second group lost tag or it broke. They are now secure in their pots and if I’m lucky they may grow some new roots.

[Dulcinea]

This is the second orchid unpotted.

[Dulcinea]

These are photos of a large brassavola that was in a hanging pot. I separated it into six plants. Please note the black at the base of two pseudobulbs

[Dulcinea]

Would I be right to use Phos on these plants? If not what? I will also use calcium. Are small oyster shell pieces ok?

[SouthPark]

Dulcinea ----- good job with unpotting and checking the roots.

You mention 'phos'. But just double-checking ------- does that refer to phosphorous acid? Such as agri-fos.

It should be ok (as in no harm) to spray the whole plant with something like agri-fos or some other systematic fungicide, regardless of what's actually happening there.

Although, it will be important to consider possible causes for the major root rot - such as whether the roots and media are getting overly wet for relatively long amounts of time.