Persistent bacterial infection
 

I am gradually losing some of my plants to an infection that starts out as dark brown patches on leaves, and proceeds to leaves yellowing and dropping off. What should I do? I have tried a couple of applications of Physan but no luck yet.


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I believe I have something similar, I treated with rubbing alcohol. Sprayed on, avoiding roots and blooms.

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I ordered this, taking Ray's advice

Amazon.com: Biosafe 600232 Zerotol Ready to Spray Fungicide/Bactericide, 32-Ounce: Patio, Lawn & Garden

We heard Alan Koch of Gold Country Orchids recommend opening a new bottle of 3% hydrogen peroxide, and pouring it over the entire plant including medium making sure it is all well rinsed. He recommends buying small bottles (12-16 oz/350-450 cc) and using each one in a single application (never storing it after opening), repeating several days apart as necessary.

By coincidence, shortly after hearing that talk, we had a small Phal. pantherina that developed crown rot. We followed his advice, and 2 years later the plant is looking good. It's only a single data point, but we were impressed.

Steve

I find this to be helpful.
Orchid Diseases

Bill

Use (and bookmark) the link Bill posted - it's an excellent source of disease diagnostic photos, with treatment recommendations (I also have it posted on my "Free Info" page, if you lost this thread).

What you're seeing could be bacterial or fungal, and it sounds like it's well established within your plants, making topical treatments of little use. Once you get a closer idea of the cause of the issue, you should seek a systemic treatment.

Steve - Alan has been a long-time advocate of hydrogen peroxide, not only as a disinfectant, but as a medium oxygenator, as well. Unfortunately, it's not as effective as a disinfectant as other stuff.

Medicinal H2O2 is stabilized with a minute amount of tin chloride, but only so it won't decompose in the bottle (which means Alan's advice of not reclosing and reusing a bottle is not really valid). Once it is poured onto the plant, it reacts immediately, releasing the oxygen, and leaving a pool of water, requiring that it be allowed to dry, or it becomes a new breeding ground. (I tilt the plants to pour it out after treatment.)

Even more effective is Oxidate (hand-held spray bottle) or Zero-Tol (hose-end sprayer), which are both H2O2 stabilized with peroxyacetic acid. That stabilizer keeps the H2O2 active until it is dry, precluding the "pool of water" concerns.

Thanks for the link - I think I am dealing with Anthracnose.


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Ray,
I was looking at Oxidate in your catalog. How is it used? Do you saturate the media and cover the leaves or spot treat? How many treatments does one spray bottle hold (I know that is relative)?

TIA, AYM

Hi Ray,
Would the Oxidate take care of Anth. ?

I was without AC for a week and a bunch of my plants aren't doing well. I can't find other fungicides besides a copper spray and Phyton. Which do you think would work best. I am going to post pictures in this part of the forum later.

Can Anth. spread to plants in different parts of the house without contam. by clippers?
Thanks,
SJF

I have used isopropyl alcohol with success but it needs to be reapplied twice a day. I had brown rot and black rot hit my cattleyas (and a few others). I used surgery and then kept disinfecting/drying with the alcohol. I caught the brown rot quickly and only the one cattleya was infected and it lost the growth that was infected but has recovered nicely. Make certain your plants have good nutrition and airflow, keep the leaves dry, and plant them higher to help prevent more infections. I, personally, did not have much luck with peroxide. The alcohol isn't good for roots or flowers but the rest of the infected orchid should be swabbed down very well after the infected part is removed.

Ray,

You force me to confess. Since I used Alan's name as the originator of that procedure, I felt I should give it as we heard it from him. And since his approach is simple and 3% H2O2 is very cheap, it avoided going into complexities about storage conditions, contamination, etc. Poor storage or even a tiny amount of the wrong sort of contamination can degrade a peroxide solution very quickly (and I know you already know that, so I'm just saying it for anyone else who might not).

My wife and I, on the other hand, both have fairly decent backgrounds in chemistry and good lab technique, and we know that if we are careful not to contaminate the H2O2 bottle during use and store it properly, it will still be usable for some time. So we only apply as much as we need and do store the rest, for up to a couple of months. (It's probably usable for considerably longer but I have no simple way to measure the degradation over time. We're also perfectly comfortable using unopened bottles that have been on the shelf for a year or more.)

I will have to look up the SnCl2 thing, as I thought for some reason that it was other Sn compounds (stannates) used as stablizers and that SnCl2 was a catalyzer for peroxide reactions. I learn something every day.

Steve