Being an amateur orchid grower, one is always faced with many challenges. There is the unpredictably rough weather, the occasional bug, the looks-gorgeous-in-Google-but-does-nothing-in-my-home stubbornness of some species, and of course, nasty rots. Like the one that I’m battling right now.

It’s a leaf spot disease that has devastated most of my young orchids. Here is what I mean:

These sunken, brown spots will cause the leaf to turn yellow and fall off.


The canes are not spared. Small black or brown spots first appear, but don’t pass them off. They get larger in a matter of days. You can see that the base of this cane is also starting to turn brown.


It can destroy pseudobulbs, like in this case. The new shoot has withered. My precious Dendrobium violaceoflavens!


In severe cases, the sunken, the spotty patches turn brown and black. The infected leaf dies, and the entire cane withers. Murder most horrid!


The infection is worst and most prevalent on my dendrobiums, followed by soft-leaved oncidiums, phalaenopses, and vandas. Paphiopedilums are the least affected. The disease spreads fast and the rain isn’t helping.  I had to do something quickly!

A fungus?

When it comes to orchid leaf spots, a fungal pathogen is what first comes to mind. The usual suspects are Phyllosticta, a disease that infects and marks the leaves with black spots, or Anthracnose, a fungal disease that typically creates black rings on leaves. I suspect this could be the latter and a very severe case of it.

Without waiting till the weekend, I proceeded to:

  1. Sterilise a sharp blade and sacateurs with a lighter,
  2. Using either of the above, cut away the infected parts, making sure to leave a margin between the damaged spots and clean tissue.
  3. Discard the infected leaves in a bin (better yet, burn them if you could) including those that have dropped off on their own.

Next, out came the fungicides. In rotation and a week apart, I sprayed my orchids with mancozeb, thiram and thiophanate-methyl, all broad-spectrum fungicides recommended for a variety of fungus diseases (do follow the instructions on the labels carefully).

Then, I waited and observed if the spots stopped.

Much to my dismay, they didn’t. Fresh spots appeared as though the fungicides did nothing! But I’m not giving up.

Not wanting to rule anything out, and with so much to lose, I decided that this might be a bacterial infection and to treat it as such. They don’t sell garden bacteriacides here, so a little improvisation is in order. I do not know if this will work, but I’m prepared to risk it to save my plants.

Here’s what I did:


I grabbed an iodine-based disinfecting mouthwash and poured a little of it into a small cup. ‘A mouthwash?’ you might ask. Yes, it’s the only thing I had at this point. It’s the iodine that I wanted.


The golden brown iodine solution is an antiseptic, or so I’ve been told by my late grandfather, which happens to be true in this case.


Next, I soaked some of it up with a small paintbrush.


And painted the parts where I’ve cut off the infection with this iodine solution.


Where I could not cut the spots off, I just painted over the spots.


It has come to the point where it’s the iodine-mouthwash dab or nothing. Hope it works, fingers crossed.

If this ends up with more harm then good, I’m prepared to try the non-chemical route such as cinnamon, or a biological inoculator next, which I’ve read, has given some growers positive results.

Of course, the last thing I could do is to cut losses, toss the plants and start over. That would be drastic.