Rot on Cattleya rex?

[estación seca]

I have dieback of new growths sometimes when I go out of town during warm times of the year, and I don't return in time to water the plants.

If it has grown for a long enough period of time, a Cattleya shoot that turns black and dies back may have produced enough rhizome to make the next new growth from the base of the partially-dead shoot. I don't remove these blackened growths for this reason.

[SouthPark]

I keep various treatments over here -like phosphorous acid solution (eg. equivalent of monterey garden phos).

A spray onto the whole new growth (or maybe copper solution if we haven't got the phosphorous acid solution) ------ followed by letting it the injured regions dry, and then also considering monthly application of mag-cal ----- and keeping an eye on the plant - would be one way to go.

The other consideration is the condition described - where you mentioned the orchid was dry - not watered for four days or something. And then - somehow - a lot of water gets in ------- we heard of 'edema' on leaves of orchids. Not sure if the same can occur with bulbs ...... maybe it can too.

Originally Posted by Leo H.

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.

That's promising. Maybe need to check on it ----- about element deficiencies ----- as in how the orchid responds if there is such deficiency. Eg ------ the photos show a region on the new growth that abruptly became sunken significantly, or caved-in, which doesn't seem to align with health degradation due to an element deficiency.

[Leo H.]

I think in this case the Calcium deficiency would not be caused by a lack of Calcium in the whole plant, but by an issue to transport it into the developping cells.

But I agree, this set in very fast which generally speaking is not normal for deficiencies.

[isurus79]

Looks like mechanical damage to me. I wouldn't worry about it.

No need to treat for algae or add copper either. Just continue to treat the plant as you already have.