Rot on Cattleya rex?

[Leo H.]

Hi,

I just noticed a black spot on my Cattleya rexe's new growth. It wasn't there yesterday when I repotted it, I just saw an area of a slightly darker shade of green which I thought was mechanical damage.

Should I remove the growth?

PS: The plant looks quite dehydrated because I did not water it for four days in the hot weather due to absence. I had this degree of dehydration before and it never hurt the plant if I soaked it right away (I did wait a day because of the repotting).

[My Green Pets]

It could be bruising from repotting, only you will know how much impact the plant sustained.
I would wait another day to see how the brown spot changes. If it gets bigger and starts oozing droplets of brown juice, it is rot and the whole growth should (unfortunately) be removed. Please post another photo that centers on the brown spots, close-up; they are not easily seen in this photo.

[Leo H.]

Here is the best I can do:

[My Green Pets]

The new photos make me think they are impact damage and not rot. But again, watch them for a couple of days. You will know if it is rot because it will grow very fast and look 'wet'. Be sure to keep those areas dry because even if they are only impact wounds, they could easily become infected. Good luck and keep us updated.

[estación seca]

If Catts don't get enough water when pushing new growths, the new growths can turn black. I think this is a possibility.

[SouthPark]

Originally Posted by Leo H.

I just saw an area of a slightly darker shade of green which I thought was mechanical damage.

If mechanical damage is suspected - especially when you mentioned a repot ----- then that is possibly due to the orchid having been bumped/knocked ----- hard to say if that happened or not though.

Another thing we can see in the pic is that the roots appear to be very dark green indeed. Is that due to algae?

Also ----- if you do happen to suspect that patch is rot, then it wouldn't hurt to spray some copper solution (for plants/orchids) on that area.

And also could provide some details about the growing area. Any gentle air-movement? How much light does the orchid get, and for roughly how long each day etc.

Originally Posted by Leo H.

Should I remove the growth?

Don't remove the growth ----- at least not at this stage. Gently nudge that area with your finger(s) to see if it's hard ..... or soft/mushy.

[Leo H.]

Hello,

yes, there is alagae on the roots, but those are the roots it already had when I got it from the nursery last year. They keept it fairly moist there, so that is why the roots appear green.
Great tip with the copper solution! If it doesn't hurt, why not?
The growing envoronment is very bright, the sun gets filtered only very lightly. But the growth was never directly exposed to it (points away from the window), so sunburn is unlikely in my opinion. It gets the maximum amount of light from 1:30 PM to 8 PM, the daylength is 16h. There is always a fan running.

It feels sunken, but not very soft, the best description would be leathery.

Kind regards,
Leo

Edit: Typo

[estación seca]

That sounds more and more like inadequate watering. Leafmite often points out blackening of new Cattleya shoots can be caused by calcium deficiency.

[SouthPark]

Originally Posted by Leo H.

It feels sunken, but not very soft, the best description would be leathery.

That sounds promising. If you just monitor the situation and keep the stem dry, and if that damaged portion dries up, then the growth can just keep growing nicely.

Also could look into mag-cal applications. I'm sure you were careful with the new growth while repotting.

Although - you did mention this occurred overnight ------ which is rather quick.

[Leo H.]

The plant is soaked now and its bulb are plumber, so if it is Calcium deficiency, the cause should be gone now.

Thanks for the information, I totally missed your first post . I was not aware Calcium deficiency can cause these symptoms!

The spots have not changed in the last 24h which makes me very happy and is another hint for Calcium deficiency because the plant received water around this time.