Black Rot?

[brsucculents]

I just took these photos for a friend and thought I would post them here. I believe it's black rot. Can anyone confirm this? I plan on Subduing the problem.
Pic 1:The first picture is a pic of the entire plant with one spot on 3 stems. This past Summer I removed a couple of leads because black spot was spreading from the stem to the rhizome.
Pic 2: This spot was left over from the Summer. I left it on the plant because it didn't spread.
Pic 3: This spot formed in the past couple of days. It started looking like pic 4 and in two days was across the entire plant.
Pic 4: This is another stem which I just noticed. I suspect it will look like pic 3 soon.

[brsucculents]

Here is a pic of another plant. I discovered the black mark while removing the sheath. The spot much have been there for a while becuase the new lead formed on an eye two stems to the right. I'm not sure why black rot would stop spreading or become dormant.

[Leafmite]

To be honest, I cannot tell from the picture. When I had Black rot, the lower part of the stem turned black. It also spread pretty quickly throughout the remaining pseudobulbs. Hopefully, this is just something else.
To prevent black rot, make certain that you add extra calcium and keep the pseudobulbs on top of the medium. Yeah, I learned this the hard way. That is why I try to tell everyone how to prevent it. :|
Incidentally, the first victim of the 'Black Plague' for me was my Brassavola nodosa.

[WhiteRabbit]

Are the spots soft?

[euplusia]

Especially pic 3 is highly suspicious, in particular because it formed fast in wintertime. A generous use of a sterilized sharp razor blade is faster and more effective than a systemic fungizide in this stage.
I totally agree with leafmite to supply sufficient Calcium to strengthen the cell walls. Most fungi are opportunistic and can only overwhelm a plant in times of reduced growth and/or stress.

[brsucculents]

It's not mushy like a bacterial infection.
A couple of months ago I bought some Calcium Nitrate and used it. How often do you recommend watering with it? Once a month?

[Leafmite]

It depends on how much is already in your water and how often you water (calcium can be easily washed away). I usually use egg/oyster shell for a slow release of calcium but, when the orchids are outside for the summer, if we get quite a bit of rain or have hotter than normal weather (causing faster growth and more watering), I add calcium to my water. Hopefully, someone can give you the advice you need.

Here are two useful sites:

Orchid Pests, Orchid Diseases
http://www.vaos.org/vaosblog/wp-cont...SueBottom1.pdf

[King_of_orchid_growing:)]

On top of the calcium advice, also try reducing the amount of water the plant receives in general.

Btw, Brassavola nodosa can also grow as a lithophyte and has been observed growing as such in the wild. You'll find the photos by doing a search on the internet.

[Ray]

That's certainly not a calcium deficiency.

Calcium is not translocatable within the plant; once it has been absorbed from the applied solution, it gets "locked" in place. If the calcium supply is deficient, the necrosis is displayed in the newest growth, leaf tips, not bases or in the main part of the structure.

Ray Barkalow
firstrays.com