Using bleach to kill bacterial or fungal Infection

[Roberta]

If sunburn, the damaged part will turn yellow/brown/black but the rest of the leaf is unaffected. I don't know for certain that is the problem... you are there, I'm not. But something to consider. Another thing about sunburn, if not severe it can take several days to show the damage - and spread over an area. So I wonder if that was the issue with your Cattleya. (Having not seen photos before you cut the leaf, I am only guessing). It's really important to know what you are treating before you treat.

[SouthPark]

Diane ----- good growing temperature (for the orchid) and temperature range, and adequate lighting level (and duration) and gentle-air movement (eg. natural air-movement and/or from very gentle air-movement from fans), and keeping leaves and stem dry will help cut down on chances of issues like that ..... even eliminates chances of it.

Check to see if any component mentioned above is missing from your set up.

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[estación seca]

Dendrobiums need large amounts of water during the growing season. I can see it's dessicated. There is almost zero chance you would have bacterial or fungal problems on a plant grown in a house in San Jose unless you have a powerful humidifying system. Almost all spots and discolorations in windowsill orchids are caused by light, temperature or watering issues.

[dianecty]

My original disease just came back! It spread beyond the cut portion I made. What should i do now? I put cinnamon on the cut as you can see.

[Roberta]

First question... what were you using to make the cut? Did you sterilize between cuts? Did you cut far enough below the damaged area to be cutting clean tissue (allowing a margin between the bad part and the good part)?

It's not clear from the photos how many leaves are involved, as opposed to different angles. If it were my plant, I would cut the damaged leaves near the base of the leaf (which in all cases would leave a good margin) And I would do it with single-edge single use razor blades - which make a very clean cut, and by using a new one each time there won't be cross-contamination.

Single-edge razor blades come from the paint section of your favorite home-improvement store, and are very inexpensive.

[dianecty]

I wiped the clippers with alcohol and then cut the leaves off. I did not wipe before each cut. 3 leaves were infected.

I did it! I went to Home Depot and bought those blades. I wiped each one with alcohol before cutting. I sprayed each cut with hydrogen peroxide and put cinnamon.

I am keeping my fingers crossed.

[Roberta]

Alcohol isn't a great disinfectant, especially with short contact time. A quick wipe didn't do much. So if there was a fungal issue, it possibly got spread. Yes, it'll keep until Sunday... But if you can get those blades sooner, it's better.

When I use my clippers on anything, I flame the blades with a propane torch. Just a few seconds is sufficient to totally destroy any organic material. It's rough on the blades... A clipper may last 6 months or so, then it's dull beyond sharping, and time for a replacement (but we're talking about $10 or so here, not fancy ones... not enough money to break the bank) Chemical treatments such as a bleach soak can work and the blades will last longer, but the soak needs to be 1/2 hour or more. How long? Who knows? (To use this approach you need multiple clippers so that soaking time is not compromised) That propane flame is around 3000 deg F.(1650 deg C) It does the job quickly, no question. I get the type of torch with a trigger so that i can operate it with one hand - the easier a technique is, the more likely that it will be used each and every time. (Razor blades work well on such things as the leaves, or old spikes. A thick rhizome needs the additional leverage of the clippers... sterilized)

[estación seca]

I don't think any of the plants you have show have any kind of disease. All the photos you have shown depict plants underwatered to the point they are almost dead.

The Cattleya leaves are turning black because the plant is very dying from lack of water. I don't know whether that is because the roots are bad, or it isn't getting enough water.

Neither fungicide nor antibiotic will help these plants. They need water.

The relative humidity in San Jose right now is 18%.
National Weather Service
It may be somewhat higher inside a house where people are respiring, but certainly not over 40%, unless a humidifier is in use. Fungal and bacterial diseases essentially never attack leaves at relative humidities like that, except for mildew during periods of very dry and cool weather. This is not mildew.

[dianecty]

IN my house right now, it says 28% which is very low.

Those plants that you say are almost dead. ONe is the replacement dendrobium stratiotes that the lady sold me - the one you told me was sick died. It acted the same way as the first one although not as bad.

The other ones have dead roots from overwatering from when I only had 2 plants. I was thinking of watering them now but it is already past 3P. I don't want the roots to keep rotting.

Do you live in San Jose too? It is so hot today!
My fans are on my orchids and I am perspiring so much because they have the fans not me!

[estación seca]

It was 116 F / 46C here today.