Black Spots on Orchid Leaves:
Should I be Worried?

Black spots on orchid leaves could mean one of three things: (1) the orchid was bruised during transport or handling, (2) the leaves have had access to more sunlight then they require, or (3) bacteria has infected the leaf.

Since the first two reasons are fairly easy to resolve and there’s no need to panic, this article will focus on the bacterial infection. But as a guide, brown spots can occur during rough handling, and the leaves bruised. They will recover in a month’s time.
As for sunlight, move the orchid away from direct sun, since the only commonly sold orchid that like full bright sunlight are Vandas.

There are many others, but not as widely known and accessible to the public.
yellow leaves in orchids
Image Credit: "IMG_7027" by rsteele38 is licensed under CC BY-SA 2.0
Black spots on orchid leaves are a direct result of a bacterial infection caused by Acidovorax (syn. Pseudomonas), known as Bacterial Brown Spot. The spots start off as brown smudges, minuscule in size and appear waterlogged. When pressed, the leaf will ooze sappy liquid.

This initial stage could be mistaken with overwatering, since the leaves can’t eliminate the excess water faster than the roots can absorb it. Water will cause blisters on the leaf, which eventually turn brownish-black.

Contrary to overwatering, with Bacterial Brown Spot, the infection will appear a nasty green color, slowly fading to yellow circle-like halo around the spot, then black.

Black is the final stage, when the blister sinks down into the leaf, leaving an “open pond”, or whole.

First, let’s eliminate what black spots are not.

  • If the spot is bigger than a small circle, like a black smudge that takes over 1/3 of the leaf, then you are dealing with Black Rot, not Bacterial Brown Spot.
  • If the spots are on the pseudobulbs or roots and not the leaves, then its also not Bacterial Brown Spot.
  • If the tips of the leaves are turning brown, then black, it’s not Bacterial Brown Spot. This is more common in Anthracnose, Colletotrichum & Glomerella spp.
  • If the leaf has elongated smudges that cover more than a pencil eraser size, it’s probably Guignardia Leaf Spot. These lesions will act like long, thin lines that elongate parallel to the veins of the leaf.
  • Phyllosticta Leaf Spot is more similar to Bacterial Brown Spot, starting off as small yellow spots, which later evolve to black sunken spots. The main difference here is that we are dealing with a bacterium, not a fungus. In Leaf Spot, the fungus has evolved to the reproductive state, spores will appear in the middle of these spots.

What Orchids are More Likely to Have Black Spots on Their Leaves?

Phalaenopsis are the orchids that most commonly get Bacterial Brown Spot. In Phals, this disease spreads quickly, and if not treated can spread to the crown of the orchid, killing it. In two-three weeks’ time, your orchid can die. While the black spots are only on the leaf in your Phal, then you can still save it.

In second place, come Cattleyas, but Bacterial Brown Spot isn’t as fatal in Cattleyas—for some reason unknown to me. Bacterial Brown Spot in Cattleyas will start off as yellowish-green dots on older leaves where wounds once were. They may also appear where you have removed a leaf of flower spike. Rarely do they develop into something more.

How Did the Black Spots Get on my Orchid in the First Place?

Bacteria love high humidity. They also love high temperatures. If your orchid is outside, then it might be in a place where the temperatures are too high, combined with too much humidity in the air.

If your orchid is inside… well, needless to say, I haven’t had black spots yet since there is no way on earth I can get my humidity too high, even if I tried. If you have a greenhouse, then higher humidity can be achieved.

First, move your orchid away from the humidifier. Make sure you keep the fan on even during night, so proper air circulation will evaporate any droplets that you missed when watering.
Bacteria builds up through stagnant water droplets on the top of orchid leaves. With the sun, the water acts as a magnifying glass and burns the place where it lays.
mounted orchid in trees
Image Credit: "IMG_7119" by rsteele38 is
licensed under CC BY-SA 2.0
This burnt layer no longer acts as a barrier, and bacteria enter the wound, spreading to other places along the leaf.

Avoid watering where water can splash from one orchid to the next, spotting leaves and stem. Be extra careful when watering an infected orchid—in fact, place this orchid away from your collection so it won’t contaminate the rest of your orchids.
Video: Black Spots on Orchid Leaves

How Does Bacterial Brown Spot Spread?

Acidrovax, the bacteria which cause these unsightly spots, spreads through water. It’s important that the water you are using is not “shareable”.

By this, I mean don’t reuse water that you are watering one orchid in to water another orchid. Keep watering separate and don’t soak multiple orchids in the same basin or bucket of water.

It also can be spread by the use of a contaminated misting bottle. If you touch the leaves on one orchid and mist another orchid, also touching it, then you are spreading bacteria and possible viruses, too.

Keep all your tools sterilized and clean.

Off the tangent a bit, but still important: Viruses are mainly spread by contaminated material when removing a leaf, flower spike, or roots. So always sterilize your equipment before using them, and I between different orchids.

How do I Treat Black Spots on My Orchid Leaves?

By using 3% Hydrogen Peroxide and a cotton swab, you can touch spot the areas that have been infected. If you prefer, you can swipe the upper side of the leaf, but never the underside of the orchid.

This is because the majority of the stomata (pores that allow oxygen-carbon dioxide trade) are located on the bottom of the leaf.

You can also use cinnamon, which is a natural fungicide. Mix the cinnamon you use at home to bake with, and add a few drops of water, just enough to form a paste, like glue.

With the cotton swab or spoon, spread the cinnamon paste over the spots. Just make sure that you don’t use the same spoon on different orchids.

If you prefer the more chemically-related answers, you can purchase a bactericide at your local nursery. A well-known one is Physan 20.

If the black spots are too numerous and are reaching the crown of the plant, then remove the entire leaf. Use a sterilized utensil and slice back the leaf. Apply cinnamon and spray your orchid whit Hydrogen Peroxide to clean it of any possible bacteria that are left behind.
mounted orchid on a tree
Image Credit: "Singapore - Orchids-01&" by Sheba_Also 43,000 photos is licensed under CC BY-SA 2.0
(Note: I wish I had pictures to illustrate these, but I don’t yet, since none of my orchids have black spots right now. As soon as I get better pictures for illustrations, I’ll replace the ones on this article. So, for now, enjoy beautiful blooms and not pictures of crummy, dying orchid leaves.)
If this article has helped you in any way, or provided useful information, please click the like button or comment in the section below. We always like to reach out to other people and make new friends. Sharing our experiences and stories is part of learning how to take care of orchids.

By the way, if you’re interested, check out his article on yellow leaves, which is another common problem with orchid growers. We spent a lot of time and research to put it together, to provide a well-written and comprehensive guide to treating the yellowing of orchid leaves.

Happy Cultivating!
Signature Amanda Matthews
orchid journey notebook
 Orchid Journey NOTEBOOK is an orchid tracker and planner for up to 100 orchids. This notebook is a journal that helps you write down your  observations are care.

Click this link for more information, and see how it's different from my first book, Orchid Journey.
Not sure what to read next?
Check out our previous post:
Not quite  what you wanted?
How about this one:
Click here to see a listing of all the articles on Orchideria. 
Orchideria Logo Image
Not the article you were looking for? Try searching for something else or go back to the first page with all the articles.
Indoor Orchids
Hi, there! I'm Amanda Matthews.

I write all the tutorials on Orchideria so unfortunately, I can't blame anyone else for all the spelling mistakes.   :)

By profession, I'm a theologian, author, and seminary professor, yet I  spend my free time enjoying nature hikes, building terrariums, and cultivating orchids. I also love to mountain bike on trails, dance, and play with my dog, Max.

When I'm not working on the next chapter of my book or online course, I'm exploring a new campsite to venture out into nature. Pitching a tent for the weekend with my two children while I fire up a barbecue is the best way to live.

Click here to go to my Author Page to check out my heart-wrenching memoir.

Share, but give due credit

© Orchideria 2019-2021

Plagiarism is a crime. We've worked hard to make these articles, research the information, and keep our site free, without charging memberships.

Unauthorized use and/or duplication of this material without  written permission from Amanda Matthews (the author) is strictly prohibited.

Excerpts and links may be used, provided that full and clear credit is given to Orchideria with appropriate and specific direction to the original content.
A Word About Affiliate Marketing

Orchideria.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.

This site also participates in other affiliate programs and is compensated for referring traffic and business to these companies, with no extra cost to you.

You can read more about how that works on this page.
This site is free, but if you'd like to support me and donate, I'd appreciate it. This page will explain more about donations.  I appreciate all your help and your support. Thank you!
orchid journey notebook
Notebook & Tracker
If you want a journal, check out this orchid tracker.  Check out this page for more information.
Popular Posts
These are some of the popular posts on the site. To see a list of all the articles, click the LEARN button at the top of each page.
orchid Tracker Excel Sheet
Free Excel Spreadsheet
If you want an orchid tracker as an Excel Spreadsheet, you can download this one that I made for free! Click here to go to the instruction page.

Leave a Reply

Your email address will not be published. Required fields are marked *

Orchideria Logo Image 2

Follow Orchideria:

3363 SW Chelsea Circle
Topeka, KS 66614

(913) 940-0605
linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram