Still new growth loss on Cattleya - Urgent call for input!

[bethmarie]

Well, it feels urgent to me, anyway. and probably to my cattleya.

I did a follow up thread on this one when calcium supplementation briefly seemed to work. (titled: Cattleya with blackened new growths, strange pest - follow up thread - 2/19/16)

More than a year later, I lose more new growths on this one than I keep.

What it isn't: Rot. The growths stay firm, they just blacken and die.

What it doesn't seem to be: calcium deficiency. I supplement w/ calcium each time I fertilize this plant.

What it is, peeps? This one is making me crazy. I'd pitch it if I weren't so invested in beating this mystery issue.

It is, by the way, Slc. Hazel Boyd 'sunset' x Pot Beaufort
Gold 'Susan Fender'

It ought to have a nice flower, but I'd settle for a healthy growing Cattleya. You may notice that even the new growths that do survive the black death are not particularly vigorous, tending to be smaller than the older growths that predate the blackening issue.

thank you, thank you, thank you.

[rbarata]

Aren't you over-fertilizing?

[bethmarie]

Don't believe so. I fertilize in very low quantity at most every watering. All the other plants (100 or so) get the same treatment, and they're growing without complaint.

[Orchid Whisperer]

I would still call it rot in a generic sense (since the growths are dying).

I used to see something like this when I was using a fertilizer high in N relative to lower P and K; this was before I supplied Ca too (which I do understand you are giving).

Once you have the latest black growth off, can you re-pot? YOur medium looks OK, but I am concerned the bacteria has colonized your medium. Also, can you try a terracotta pot? Possibly inorganic medium, such as "lava rock", or medium such as whole wine corks?

[bethmarie]

Will you say more about bacteria colonizing the medium? That's the first time I've heard that. I will try repotting and using inorganic medium. Thanks for the suggestion.

I'm using Dyna-Gro 7-8-6, for the record.

Appreciate your reply!

[Fernando]

Don't fertilize for a few months and keep it dry (with high RH).
That other plants don't show signs of damage doesn't mean that this in particular is not suffering from to much nutrients as it is already struggling.
My first impression when I saw the picture was 'too much fertilizing, poor light and poor ventilation' (this shrivelling little pbulb...). Than I read your text and the first answer ... yes, too much of food (which makes bacteria boost.)
As a rule of thumb, never fertilize a struggling plant. At least it seems it has still good roots. So don't do anything to loose them.

[estación seca]

I think you may not be watering enough. Cattleyas need a lot more water when pushing new shoots. If underwatered they turn black like this.

[King_of_orchid_growing:)]

I don't know if this will solve anything, but do you mind me asking how much light is this plant getting? It does not seem to be getting enough light. The leaves look too dark a shade of green to me.

[Ray]

What calcium supplement are you using; how much and how often?

[Orchid Whisperer]

Originally Posted by bethmarie

Will you say more about bacteria colonizing the medium? That's the first time I've heard that. I will try repotting and using inorganic medium. Thanks for the suggestion.

I'm using Dyna-Gro 7-8-6, for the record.

Appreciate your reply!

Any bacteria (good or bad) can be expected to spread to a degree from one place to another in an environment. What I mean by colonization is simply that bacteria from the rotted tissue could have gotten in the medium (bark, LECA, whatever) that you are growing plants in.

Think of it this way: if you have a family member that gets a staph or strep infection, you would want to make sure that you disinfect surfaces (counters, door knobs, etc.) that are shared by the rest of the family. You can disinfect pots and tools with things like Physan, peroxide, etc., but it is probably not the best idea (or economical) to drench medium with a disinfectant. More practical to un-pot, clean the plant (possibly wipe the leaves with a paper towel and peroxide), and re-pot in a clean pot with clean medium.

The dyna-gro should be fine if not over-applied. I find Ca applied as gypsum (or Plaster of Paris) adequate.