Aargh! Orchid rots. I thought I had nipped this problem in the bud when it made a nasty comeback. And when it hit, it hit big. It hit BAD. A few of my vandas succumbed, including a couple of dendrobiums. It wasn’t pretty.

How? Why?! I asked myself, frustrated and heartbroken.

The truth is, I sort of knew why. There is this anecdotal orchid mantra which states that one should never feed orchids with high nitrogen fertilisers during the rainy season. To my own folly, I did exactly that. With organic fertilisers!

Whether my mantra-defying actions had anything to do with the rots remain unproven – scientifically at least – but the timing, correlation and damage was enough to convince me that yes, it most probably was the cause. My mistake. Lesson learned.

If your orchids are grown outdoors, stay vigilant during the rainy season. Bacterial and fungal diseases are not uncommon when cultural conditions become less than ideal.

Here are the sad signs on my vanda:

Check out the crown. Brown, mushy rots on leaves growing off the apex are a sure sign of trouble:

This crown has browned. It's bad!

This crown has browned. It’s bad!

The roots also showed signs of stress. They became dessicated and died:

Root rot

Root death! Rot doesn’t necessarily mean mushy roots. Withered, dessicated roots are also a clear sign that something’s amiss.

Back to the crown – having rotten very badly, the leaf at the crown came off like wet tissues. It smelled putrid which led me to suspect that this was a bacterial infection:

Gone with the leaf. Things will only get worse.

Gone with the leaf. Things will only get worse.

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One, two, three rotten leaves. The awful gruel in the crown. The mushy parts smelled horrible! Could be bacterial (Erwinia or pseudomonas?) or fungal (Pythium, Phytophthora).

So I cut the crown off. It looked like the rot has taken hold of the stem and was working its way downward:

crownrot-7

Rotten to the core.

With a sterilised pair of sacateurs, I continued cutting the top off until I saw clean tissue:

Cut and cut, until it looks clean.

Cut and cut, until it looks clean.

I poured a bleach solution (bleach:water at 1:5 ratio) down the crown to disinfect the stem. Hydrogen peroxide will work too.

Bleach bath down the crown.

Bleach bath down the crown.

Then, I hung the vanda upside down and prayed for the best (why I do this).

To be honest, this kind of bacterial rot kills my vandas 90% of the time. I’ve tried cinnamon, peroxide, bleach solutions, microbial therapy but nothing seem to work. It is devastating and I certainly don’t wish this to befall on anybody.

These pictures were taken late last year at the height of the monsoon season. I had intended to write this post when the vanda had shown some semblance of recovery (happy news goes a long way) but I’m sad to say that this big mama was a goner. It had a keiki which I removed instantly when the infection took hold but it doesn’t look promising up to today.

The dendrobiums fell sick.

Bacterial orchid rots have infected a few of my dendrobiums too. Unlike vandas, there isn’t really a ‘crown’ to cut off. But if a young pseudobulb has rotten, it’s best to:

  1. Pull the whole plant out of its pot – the roots have most likely died and the media needs to be discarded.
  2. Excise the whole pseudobulb at its base. Treat the wound with hydrogen peroxide.
  3. Trim off the rotten roots (if any).
  4. Leave the plant in a humid spot until new pseudobulbs emerge.
  5. If and when new leads emerge with new roots, replant in fresh, clean media.
Dendrobium with signs of rot. Again, the damaged leaf smelled putrid.

Dendrobium with signs of rot. Again, the damaged leaf smelled putrid.

Because distressed dendrobiums tend to put out new leads, the survival rate for sympodial orchids are much more positive.

I’ve cleaned-up the badly infected dendrobium and left it amongst my tumeric shoots. The worst is over for it and now it has put out new plantlets.

 

Those old, dead roots that don’t function anymore and can be trimmed off. When new roots emerge from the green leads, this plant will be repotted.

But if all else fails, just throw the plant away and start anew. A badly infected plant carries the risk of infecting other vulnerable orchids, and when that happens, the scale of loss and clean-up is unimaginable.

To minimise bacterial infections, keep your growing areas are clean (but not necessarily sterile) and conditions ideal for the types of orchids you are keeping.