Cattleya: Possible fungal/bacterial infection; dots on leaves

[StanTheMan]

Hello everyone. So I got this orchid about a month ago, gorgeous blooms. It had about three backbulbs in yellow, dropped its last leave. I thought ok that's normal. Those bulbs though were soft. Then the next bulb started yellowing and the leaf picked up this ugly coloring (mind you it never was put in full sun). The seller and other orchid growers recommended me a fungicide, so on Tuesday this week (november the 9th) I sprayed it with benomyl and separated the healthy part of the infected part.

I isolated it in a big bottle with plastic wrapping (because of the toxicity), and today when opening it I find out it has these dots on the back side of the leaves. Also, the oldest bulb is kinda starting to turn lighter in color, which is what happened to the other bulbs. As you can tell, the infection moves quite rapidly in the plant.

Is there any saving for my plant or is this problem worse than I thought?





These pictures above were taken the 5th or 6th.

The following ones are taken today.



This is the oldest bulb. As you see, it seems it kinda starts to yellow on the top part of the cane.





As you can see, these dots on the back of the leaves have appeared or, if they were already there, they have become very notorious. Before this, you could maybe distinguish some somewhat darker spot all throughout the leaves, but very faint, something you'd barely notice.

Any comments are greatly appreciated.

[Roberta]

The thing that jumps out at me is the contents of the pot... maybe it is the lighting, but the mix looks old. (That weed growing in the pot also indicates that the medium is turning to mud) While it may not be the ideal time for potting (which would be the start of new roots) sometimes one has to risk a small setback to avoid fatal conditions. Catts need lots of air around their roots, so that they can pretty much dry between waterings. I would worry that there are unhealthy conditions in the pot, which could lead to rot moving up into the newer parts of the plant, and destroying roots. My advice would be to take it out of the pot and see what might be going on down there.

[StanTheMan]

I'm not sure how old the media is, but it being white lava rock, it doesn't decompose to mud. But there were some algae on the topmost bits, not much but yes. Those plants were sort of a sign it was being watered too often, since I couldn't keep them all alive with my watering program. I removed most of the old media I could when I removed the older bulbs and before spraying with fungicide. A little more dead than alive roots, but nothing extraordinary. Thank you very much for your advice )

[Roberta]

Lava rock is definitely a good medium! If it is still staying too wet, consider moving it to a container that will let it dry faster - a basket (I really like wood baskets for Catts, plastic works too), terracotta pot, etc. I totally agree that for a collection of any size, it's impossible to "customize" the watering for each plant. So begins the task of tweaking the medium/container combinations so that each gets what it wants while everything is getting watered on the same schedule.

[StanTheMan]

I hadn't moved it because, precisely, no new roots were starting at the moment, but my plan is to rather put it in a mix of bark with a little peat moss / coco peat (it's a premade mixture, it has very little of the latter and even none if I just shake it a little before adding it to the pot haha) on a nice clear pot. My environment seems to work with this setup. With lava rock, maybe I'd have to water more often, and in a basket it would demand very very frequent watering. So that is the plan for the future, but in the meantime, wish me luck for its recovery

Thanks again for your input.

[Dusty Ol' Man]

Originally Posted by StanTheMan

I hadn't moved it because, precisely, no new roots were starting at the moment, but my plan is to rather put it in a mix of bark with a little peat moss / coco peat (it's a premade mixture, it has very little of the latter and even none if I just shake it a little before adding it to the pot haha) on a nice clear pot. My environment seems to work with this setup. With lava rock, maybe I'd have to water more often, and in a basket it would demand very very frequent watering. So that is the plan for the future, but in the meantime, wish me luck for its recovery

Thanks again for your input.

When I got my Catt, it was a division from another plant. I immediately put it into semi hydroponic media in a homemade pot (empty plastic nut container). This was last spring. Since then it has taken off with first three and now five new growths and a bunch of new roots. Four of the five have grown sheathes. The fifth is just starting and is about an inch long. The semi hydro allows me to water everything at once, making watering schedules simple. It is working for me. YMMV.

[estación seca]

Originally Posted by StanTheMan

...It had about three backbulbs in yellow.... Those bulbs though were soft. Then the next bulb started yellowing and the leaf picked up this ugly coloring (mind you it never was put in full sun).

I isolated it in a big bottle with plastic wrapping (because of the toxicity), and today when opening it I find out it has these dots on the back side of the leaves.

As you can see, these dots on the back of the leaves have appeared or, if they were already there, they have become very notorious. Before this, you could maybe distinguish some somewhat darker spot all throughout the leaves, but very faint, something you'd barely notice.

Any comments are greatly appreciated.

I think you have bacterial brown spot, and not a fungus disease. It looks like this. Fungicide will not treat a bacterial disease.

This is a disease of plants kept in hot, humid conditions with poor air circulation. Unfortunately putting it into the bottle and closing with plastic was not the right thing to do.

Go to the Web page of the St Augustine Orchid Society and look at the Pests and Diseases page. Scroll down to
Bacterial Brown Spot - Acidovorax (syn. Pseudomonas)

The growth with the yellow leaf with spots is dead. I think there is a disease spreading through the plant. The treatment is to cut off all affected growths, cutting into healthy tissue. Sanitize your knife with 10% household bleach or 70% alcohol between each cut, and let the blade dry.

Then treat the plant with a disinfectant to kill the bacteria on the outer surface of the plant. The Web page above discusses what to use.

[StanTheMan]

Originally Posted by Dusty Ol' Man

When I got my Catt, it was a division from another plant. I immediately put it into semi hydroponic media in a homemade pot (empty plastic nut container). This was last spring. Since then it has taken off with first three and now five new growths and a bunch of new roots. Four of the five have grown sheathes. The fifth is just starting and is about an inch long. The semi hydro allows me to water everything at once, making watering schedules simple. It is working for me. YMMV.

Thank you very much for the idea. I have been toying around in my head with the idea of putting my Sharry Baby in semi hidro, but I'm still a little reluctant because of rot risk, let alone with Cattleyas and especially this one. I have never grown Cattleyas before, so this one, a cross between BLC Chia Lin and Cattleya lueddemanniana, and BC Fuchs Star are my first official attempts (I did inform myself extensively before online, and I'm keeping them in a nice warm room with great great light). Have a good one!

---------- Post added at 11:35 PM ---------- Previous post was at 11:31 PM ----------

Originally Posted by estación seca

I think you have bacterial brown spot, and not a fungus disease. It looks like this. Fungicide will not treat a bacterial disease.

This is a disease of plants kept in hot, humid conditions with poor air circulation. Unfortunately putting it into the bottle and closing with plastic was not the right thing to do.

Go to the Web page of the St Augustine Orchid Society and look at the Pests and Diseases page. Scroll down to
Bacterial Brown Spot - Acidovorax (syn. Pseudomonas)

The growth with the yellow leaf with spots is dead. I think there is a disease spreading through the plant. The treatment is to cut off all affected growths, cutting into healthy tissue. Sanitize your knife with 10% household bleach or 70% alcohol between each cut, and let the blade dry.

Then treat the plant with a disinfectant to kill the bacteria on the outer surface of the plant. The Web page above discusses what to use.

Hey, that link is so so helpful! Gosh, there's so much I ignore in pests and diseases... Nobody wants to deal with the nasty stuff haha, but you gotta do what you gotta do. I read your comment on my commute and I already sprayed my plant with hydrogen peroxide (searched for physan and it costs about three times more than that fungicide I bought... This plant might end up costing way more than expected, but first I wanna try the basics). Do you think it's a good idea to spray it entirely with hydrogen peroxide daily for, say, a week? Or am I being overly cautious? Should I also preventively spray my Sharry baby who was next to it for about a week? It has no signs (yet) of infection. I moved it apart the same day I took the first pics (november 5th or 6th).

Call me crazy, but when spraying it I didn't see any signs of the yellowing moving further (on the last bulb I was suspicious about), so I'm positive on this. Oh, and I never saw any "water" on the spots, but then I just gave it full attention when it got completely dark.

Thank you very much for your comments, as always. Kind regards!

[estación seca]

Healthy plants generally don't get diseases if ambient conditions are proper. Those bacteria are everywhere. The peroxide may cut down the number of viable spores, making infection less likely.

If you've already cut off the infected parts, and already treated the plant once, that should be enough. Hydrogen peroxide will oxidize living tissue so it's not good to use it a lot.

I don't suggest prophylactic treatment for diseases. Your plant probably arrived infected. The Oncidium has been growing there, and probably is healthy from good care.

[StanTheMan]

Alright then. Yesterday I didn't have time to check on it thoroughly, but from what I saw (cross my fingers but only on one hand), the oldest bulb is not turning yellow. To think I could have saved the money on that fungicide with a proper diagnose... Haha oh well, now I have it in case of future fungal attacks.

Thank you very much for your help,

Stan