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Treating Orchid Pests and Disease

For your orchids' sake, I hope you won't ever need this info., but here it is anyway - just in case.

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treat spots on orchid leaves

At one time or another, all orchid growers will have to treat orchid pests and disease. Find out how to identify problems and what actions to take. The good news is that bacterial infections and pests are usually not serious and are easy to treat. 

What you’ll learn: how to treat orchid pests and disease, including bacterial and viral infections as well as pests such as scale and mealybugs.

While attending an orchid show at the Red Butte Garden in Salt Lake City I was warned the bacterial infections are quite common on orchid leaves. I was reassured to learn that these infections are also easy to treat. Sure enough, it wasn’t long until the tell-tale black spot showed up on my orchid’s leaf. Luckily, I knew what to do.


CLICK HERE for your Troubleshooting Guide for Orchid Pests and Disease – Identify – Treat – Prevent.


This-totally-worked-the-black-spots-on-my-orchid-leaves-are-gone - treat orchid pests and disease

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The First Line of Defense is Prevention

4 Tips for Preventing Disease

  1. Buy healthy plants.  Before making a purchase inspect leaves for reddish-brown to black spots. Do not buy plants with spotted leaves (like those in the above photo). 
  2. Provide air circulation.  Orchids love humidity, and so does bacteria.  To prevent diseases that thrive in a humid environment, turn on a fan. Air circulation will do wonders in preventing bacterial growth. 
  3. Avoid overwatering.  Besides killing your orchid’s roots, standing water is like sending an invitation to unwanted bacteria to come to live in your orchids. 

    Watering Orchids: Find Out What Works

    Learn how to water correctly and you'll avoid the #1 cause of orchid death

    Read
  4. Isolation.  As an extra precaution isolate new plants for a week or two, just to be sure that it didn’t bring any hitchhikers, in the form disease, along. This advice has saved my orchids. Sometimes we may overlook bacterial spots, that somehow become glaringly obvious once at home.

Identify the disease or pest

If you do notice something unusual, the first step is to identify the problem so that you can apply proper treatment.

Bacterial: Treating Black Spots on Orchid Leaves

Bacteria can be identified by a reddish-brown, or black spot on the orchid leaves.  The spot may be quite tiny, like little freckles sprinkled on the leaf, or larger, with a lighter ring around the edge.

Use Hydrogen Peroxide to Treat Bacteria

Full strength hydrogen peroxide can be used and will kill the bacteria that causes black spots on orchid leaves.  Simply soak a Q-tip with hydrogen peroxide and dab affected area(s). Avoid swabbing underneath the leaf, as this may kill the leaf. (Having bathed the underside of an orchid leaf in hydrogen peroxide, I know the truth of that statement.)

hydrogen-peroxide-to-treat-bacterial-infections-on-orchids - treat orchid pests and disease

apply-hydrogen-peroxide-to-affected-area-on-orchid-leaf.png

Use Cinnamon to Treat and Prevent Bacteria

Another or additional, option to treating black spots on orchid leaves is to make a cinnamon paste.  Cinnamon possesses antibacterial properties, making it a natural choice to treat bacteria. Plus, it’s something that’s on-hand. Mix powdered cinnamon with water, or Elmer’s glue, until it forms a paste consistency.  With a Q-tip, swab the paste onto the affected area. Once again, swab just the top side of the leaf.

cinnamon-paste-treats-spots-on-orchid-leaves - treat orchid pests and disease

cinnamon-paste-on-Q-tip-ready-to-apply-on-infected-orchid-leaf.png

spots.jpg

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If Your Orchid has a leaf that looks bad – cut it off

Trimming off the affected area with a pair of sterilized scissors is another option.  To sterilize scissors, wipe them down with a cotton ball soaked in rubbing alcohol. When making the cut, be sure trim about 1 cm. past the black spot.  If the entire leaf is affected, cut off the whole leaf at the base. The black spot on the below leaf was quite large and near the crown of the orchid. I trimmed the entire leaf off as close to the crown as I could.

trimmed-off-this-orchid-leaf.png

Identify and Treat Sunburn

Sunburned orchid leaves results in destroying the leaf tissue. At first, the leaf will just feel squishy. Over time, the least will continue to deteriorate and the leaf will turn from green to brown, and, eventually, black.

The best course of action is to remove the sunburned leaf with sterilized shears or a single edge razor blade. Apply a cinnamon paste to the lesion. 

Use care not to expose the orchid to the possibility of sunburn. If you suspect sunburn, move your orchid further away from the window or light. Never leave your orchid in your car.

sunburned-orchid-leaf.png

In this photo, the orchid leaf is blushing pink from the sun but is not sunburned.

orchid leaf sunburn

In this photo, the leaf has been sunburned and the leaf tissue has been destroyed.

Identifying Virus

This is the bad news: Viruses can be difficult to diagnose and almost impossible to cure.  Viruses can be identified by a color break in blooms.  The best course is to throw out such plants. If you don’t want to throw out your orchid, keep it away from your other plants. Use caution and keep all tools (watering cans, razor blades, etc.) away from the infected orchid. If you do use a razor blade, be sure to throw it out after use.

TIP: To accurately identify a virus you must take a sample and send it to a commercial lab such as agdia

Now You’ve Got Black-Spot Removal Know-How

Now that you know what those little black spots are, you are ready to take action if ever the need arises. Black spots on orchid leaves are easy to treat and can be taken care of with items you probably already have on hand, no need to run to the store. Just for the record, I have had more success with treating black bacterial spots with hydrogen peroxide than I have with cinnamon.

Pests: Mealybugs and Scale

Just the words scale and mealybugs give me a shiver of distaste! These little beasts can easily spread throughout an entire collection if you’re not careful. The first step is to identify these bugs. If you notice any sort of pest, immediately remove the orchid away from the rest of your orchid collection.

Mealybugs

If you notice a cottony, web-like substance around the base of the plant on pseudobulbs, rhizomes,  or on the underside of leaves you may have mealybugs. Another tip-off is the presence of ants. Mealybugs excrete honeydew that attracts ants. 

Scale

Scale, particularly armored or Boisduval is considered the worst of orchid pests. Unlike mealy bugs, you can’t simply use your fingers to brush the scale away. The scale has a thick detached shell that is practically cemented to the orchid. Look on leaves, and all around the base of the plant, for signs of this pest. Scale can be difficult to get rid of because they hide in every imaginable nook and cranny. Repeated treatment is recommended.

Identifying scale: Hard light, brown bumps that you can not scrape away indicate Boisduval scale.

Treatment for both mealybugs and scale:

  • First, isolate these orchids from the rest of your collection.
  • Second, spray the plant with horticulture oil. This is most effective when bugs are in the nymph phase.
  • Third, with an old toothbrush and 70% rubbing alcohol, and a pair of surgical gloves scrub every nook and cranny of your orchid. This may seem overwhelming when you first look at your orchid, especially of your orchid is large, with lots of leaves and pseudobulbs, but you can do it. Once you get started, it’s not so bad.

I recommend pouring a small amount of rubbing alcohol into a dish so that you can easily dip the toothbrush into the bowl without contaminating the rest of the alcohol.

orchid pests - scale

The orchid leaf of this Miltoniopsis orchid is covered in Boisduval scale.

treat orchid pests - scale

Materials needed to treat scale and mealybugs: 70% rubbing alcohol, a small dish to use to hold alcohol, toothbrush, surgical gloves.

treat scale and mealy bugs

Dip the toothbrush into the dish with alcohol and scrub every nook and cranny of the orchid.

Keep the toothbrush and alcohol on hand so that you can repeat the process every 10 days, or sooner if you see signs of the bugs. After the scale has been treated the hard shells will dry up and easily flake off, though a scar will remain.

If you suspect that pests are down in the orchids roots and soil you can safely pour hydrogen peroxide in the potting mix. As this will dry out the roots, be sure to water thoroughly water afterwards.

Bugs Are No Fun – But Are Treatable

Bugs are a huge nuisance, but you can take action against them. As soon as you notice them, begin treatment right away. As always, an ounce of prevention is worth a pound of cure: Check new plants for signs of pests before purchasing. Keep new plants away from other plants until you are sure the plant is healthy and pest free.

Now you know how to treat orchid pests and disease. I have confidence that you’ll be able to with the tools we’ve talked about you’ll be able to successfully eradicate these common pests and disease.


CLICK HERE for your Troubleshooting Guide for Orchid Pests and Disease – Identify – Treat – Prevent.


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46 Comments
  1. maya Hira says:

    where can I get this house happy orchid, without going to nursery.they very expensive in nursery.

    1. Anna says:

      Maya,
      If you happen to have a Trader Joes nearby you can find a selection of orchids at a good price.
      Anna

      1. Zac Nibarger says:

        Hello I had these tiny little white bugs very small I think that they were thips and i got something to take care of them then I washed the roots sprayed them with pest a side and reported the plant in a little bit bigger of a pot and i have not seen the pest but now I have another problem the two stalks that are growing one of the stocks is flowering and the other one has some new growth but on the stalk that has new growth the top of the stalk is getting brown and every day it is worse at first i cut the the stalk to get rid of the brown but now the green stalk is slowly turning brown. the stalk that is turning brown has not reach the new growth but it probably will in 5 to 6 days more and i am worried because i don’t know what to do. I would send photos if that would help.

        1. Anna says:

          Zac,
          I recommend just cutting down the stalk that is turning brown and waiting for a new, vigourous flower stalk to grow in its place.
          All the best,
          Anna

  2. Anonymous says:

    Many thanks for all your tips. Barbara

    1. Anna says:

      Your welcome Barbara! I’m always glad to help.
      Anna

  3. Jeremy says:

    Hello my Orchid was very healthy and now it is developing black spots. I think my moisture level might have been to high. Would anyone be willing to look at a picture of the plant and add any advice?

    Cheers

    Jeremy

    1. Anna says:

      Jeremy,
      Turning a fan on low, will help prevent bacterial growth on the leaves by adding some air circulation.
      Check out this post for more information:
      https://www.orchidbliss.com/temperature-air-circulation/
      Also some varieties, Oncidiums come to mind, are particularly prone to black spots.
      Email me at [email protected], I’d love to see a picture of your orchid.
      Anna

  4. Sandi says:

    Where can I find horticulture oil? Speciality store or big box in garden section? Thanks you!

    1. Anna says:

      Sandi,
      I purchased my horticulture oil through Amazon. Here is a link for the oil that I purchased. At no additional cost to you, I will receive a commission if you purchase through that link.
      Horticulture Oil
      I’m so sorry that you are in need of horticulture oil!
      Best of luck getting rid the pests tormenting your orchids!
      Anna

  5. Sinead Louise O'Sullivan says:

    Help!! Never had much luck with orchids and my mum brought me one for mothers day. I inspected the plant the next day and noticed miuld/algae in the pot. The roots still look mostly green but I have noticed on the underside of some of the leaves are some little black mouldy looking spots….not much but enough to worry me. My orchid is in bloom and still has buds so from what I have read they say to avoid replanting. Help….don’t want to loose another one. Do I replant or just treat the algae.

    1. Anna says:

      Sinead,
      Thanks for reaching out. There is an easy fix to getting rid of mold. Apply a bit of hydrogen peroxide, lemon juice or horticulture oil to the mold. Wait a few days and reapply as needed.
      Anna

  6. Jennifer says:

    I have a orchid that was given to me by my next door neighbor who was moving. I noticed this white stuff on the leaves and stems. Any idea what this could be. Its a old orchid

    1. Anna says:

      Jennifer,
      Could you send me a picture? Email me at: [email protected].
      I’m happy to help you figure this out.
      Thanks,
      Anna

  7. Katiusca Gonzalez says:

    Hola, buenas noches, quisiera enviarte unas imágenes de cuatro de mis orquídeas, las cuales presentan una infección y realmente no se que es, y necesito ayuda, que tengo que hacer para poder mostrártelas? g
    racias

    1. Anna says:

      Katiusca,
      To send me images, email me at [email protected]
      Thanks,
      Anna

  8. Jennifer says:

    I emailed you 3 pictures. Its a very old orchid. She had it outside one her fince for many years.

    1. Anna says:

      Jennifer,
      Thanks for sending me the pictures. Check your inbox for my reply. Pictures are always helpful.
      Have a great day,
      Anna

  9. Rima Ngatoa says:

    I have two phalaenopsis plants, just finished blooming. I would like to thank you for sharing a lot of information on caring orchids, especially the phalaenopsis. Thank you very much, very helpful indeed.

    1. Anna says:

      Rima,
      You are very welcome! I am glad I could help. Phalaenopsis orchids are rewarding orchids to grow. Their long-lasting flowers make them a real joy to care for.
      Yours,
      Anna

  10. Tina Fuller says:

    You always have such great tips. Can you suggest how to safety treat an orchid I have on a piece of driftwood without hurting the orchid? My orchids are outside in a shed so the ants might just move from one orchid to another. Thanks for any info you can send my way. Tina

    1. Anna says:

      Tina,
      To keep ants away you could set the orchid pot in a dish of water. Just make sure that the orchid is in an outer pot so that the roots aren’t sitting in water. This should keep the ants from getting into your orchids.
      Have a great day,
      Anna

  11. H P says:

    How long do you leave the cinnamon on the leaves?

    1. Anna says:

      H P,
      I don’t have an exact timetable. After a few days wipe the cinnamon off, if you still see black spots, reapply as necessary. Cinnamon really is an effective and safe fungicide.
      Best,
      Anna

  12. Marj says:

    Thank you for your tips! Im a newbie when it comes to orchids. My orchid just finished blooming ang is now growing new shoots. However i saw a black spot at one of the old leaves. How often do i apply it? Is daily apply application safe? Thanks,

    1. Anna says:

      Marj,
      After you have applied the hydrogen peroxide or cinnamon, wait to see if the brown spot is still soft and watery. You could simply remove the leaf, cutting about a centimeter past the damaged tissue with sterilized scissors. Apply cinnamon to leaf edge where the cut was made.

      A word about prevention: Your orchid’s best defense against bacterial brown spotting is good air movement. A small fan, set to the lowest setting and pointed away from the orchid will do wonders in preveting bacterial and fungal growth.

      Best,
      Anna

  13. Angela Bass says:

    I have had my first orchid for a little over a year. It’s on it’s second bloom. Now I find myself hunting the throw-away discount section for cheap ones to take home and love. I now have 6. How do you stop wanting to give love to the unloved? My husband is nervous. I just keep adopting plants and I now have a mini jungle.

    1. Anna says:

      Angela,
      I love it! You’ve got the orchid bug and there is no help for it – it’s incurable. I have found that resuced and rehabilitated orchids do make excellent gifts and make room for more orchids.
      Best of luck,
      Anna

  14. Rhonda Arnold says:

    I appreciate your knowledge and advice. Thank you for taking the time to share what you’ve learned about orchids with us.
    Rhonda

    1. Anna says:

      Thank you, Rhonda!
      All my best,
      Anna

  15. Geraldine says:

    I think I have learned a lot about orchids. I bought one about a year ago and finally, the blooms died off and all I did was water it. I would like to try and get it to bloom again the root is growing out of the pot and some are dead so I will take it out of the pot and cut them out and re-pot it again.

    1. Anna says:

      Geraldine,
      Sounds perfect! If you need help potting your orchid, click on the link below:

      HOW TO POT AN ORCHID

      Best,
      Anna

  16. sue says:

    I need help … my orchid has a very sandpaper roughness on its underside of the leaf. I can’t see any bugs it’s white-ish in color and it’s not mealybugs. It’s like the bottom of the leaf is gone.

    1. Anna says:

      Sue,
      Without a picture, it is hard to tell what is wrong, but it sure sounds like scale. The above article describes how to treat scale. Take action quickly and if you have other orchids, be sure to quarantine the orchid with scale and carefully examine your other orchids for the pest.
      Wishing you all the best,
      Anna

  17. Rebecca says:

    Hello!
    Thank you for your tips, I have mealybugs and am trying to find the best way to get rid of them fast and as easy as possible, other than the alcohol, should I replant my orchid?

    1. Anna says:

      Rebecca,
      You can get mealybug destroyer ladybugs as a natural control. Be sure to place the orchid in a clear dry cleaner bag so that the ladybugs don’t just fly away.
      Here is a link to get you started:
      LADYBUGS
      Best wishes,
      Anna

  18. Anonymous says:

    Thank you Anna for helping me to deal with scale.
    Celia from Jamaica

    1. Anna says:

      Celia,
      Scale is no fun! I am glad you’ve been able to get it under control.
      Best,
      Anna

  19. Marie says:

    Hello Anna,
    I need help…..an orchid that I purchased around the holiday season and has been in bloom all this time is suddenly in distress. and, yes, it is still in bloom – however,
    earlier this week, one of the large leaves fell off – it’s just sitting on the table. didn’t even get moved/touched. and it was slightly discolored – like the older leaves do when they are turning color. just today, now, about 5 days later, this plant is still in the same place getting the light it needs, etc., and I noticed that the 2nd leaf is laying on the table. uh, oh – I decide to “really” look at it.

    I noticed when I took the plastic pot out of the decorative one that it’s full of the moss and the roots are looking squashed and like they are tired. I poked my little finger up through the bottom hole and it is damp. I have watched lots of u-tubes on the care, the potting, what to look for, as well as following along all your very informative “tips” to know that this plant is in distress. so, I carefully remove it from the plastic liner and nothing seems to want to move. I got a large plastic container (I keep the large plastic covers that one gets when buying a cake in the grocery store as I have found them to be very helpful when working with plants, etc. and then I don’t destroy any of the better food storage containers) – anyway – I took it to the sink and with just tepid water, I slowly lowered the plant into the container to sit for a few minutes. I then drained the water and started to very carefully remove all of the moss. No wonder the plant was crying out for help – it was packed in there solid! That whole plastic container was filled almost to the top with the moss. I noticed that some of the root system came with the moss – I guess they were truly dead. However, for the most part, the plant has lots of roots and to me, they do look salvageable. I got all the material off the roots and rinsed well under the tepid water and it is now resting.

    I am hoping I am following good protocol with this plant. I have a new medium – some moss but mostly bark that I will now repot it into.

    I guess I’m looking for some direction here from you to know that I’m doing the right thing. the other thing is – it is still in full bloom and I surely hate to cut them off – but if it’s advisable, then that is what I will do.

    I have attached some pictures so you will see just what I’m talking about. Any help you can provide would be greatly appreciated.

    Marie

    Marie

    1. Anna says:

      Marie,
      You are doing the right thing by re-potting. Be aware that the orchid will have to recover from re-potting and may lose its flowers. But, maybe not, so there is no need to cut off the flower spike unless the flowers begin to fade.
      Good job getting to the root of the problem 😉
      Amma

  20. Renee Andres says:

    Hello!
    I have abouut 6 orchids and 3 of them are infected with this weird red mold or fungus in the soil and I can’t find anything on the internet telling me what it is or how to treat it. Please help me!
    Renee

    1. Anna says:

      Renee,
      Apply a horticulture oil to treat the fungal or bacterial infection. Reapply weekly. You could start with one orchid and see how it responds to the treatment before treating all three orchids. Also, keep the infected orchids away from the healthy orchids and sanitize your tools.
      Best,
      Anna

  21. Violet BLACKLER says:

    I have an orchids that never blooms but grows lots of roots looks healthy nice firm leaves should I throw it out?

    1. Anna says:

      Violet,
      Your orchid just needs a few care tweaks and it should bloom. The two things it likely needs is more light and possibly a change in temperature. Check out these two posts and apply what you learn. I’m confident you’ll be able to get your orchid to flower.
      LIGHT
      TEMPERATURE
      Best,
      Anna

  22. Debbie says:

    Hello,
    I purchased an orchid online and received it about a week ago. The post office was supposed to hold it for pick up since I am in Arizona and it is very hot right now. The orchid was delivered and left at the front door in the sun in it’s shipping box. It seemed to be okay and was packed well but was very warm. I put it on my kitchen counter to cool down and it seemed okay. Imagine my shock when I looked at it a couple of days later and it is turning black. Is this heat damage? I have separated it from my other orchids.

    1. Anna says:

      Debbie,
      I am sure it was heat damage. I’m so sorry!
      Best,
      Anna

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the ONE email you'll open every week

Saturday mornings I send out an exclusive email sharing my best tips on how to grow healthy orchids.

YES! THANK YOU!