Is this Erwinia?

[greenhouseFrog]

This yellowing wet spot on this Oncidium’s new growth eluded me until today—upon discovery, I noticed it had spread down into the crown of the new growth, as well as towards its base. The yellow portions are smelly and mushy—the bigger leaf kind of sloughed off after the pictures

Should I just remove the infected growth as cleanly as possible and douse the remaining(hopefully uninfected) plant in something like Physan? Also, should I spray down everyone else that was in proximity of this one?

Thank you in advance for your input!

[Ray]

It could be. If it has a bad odor, then that's probably for sure.

Yes, cut off the leave below the infection and dab the wound with a q-tip dipped in cinnamon poweder (don't get any on the roots).

That is a systemic bacterial infection, so a topical treatment like Physan will have no effect on the infected plant. You'd do better with a copper-based treatment, since they are systemic.

[greenhouseFrog]

Originally Posted by Ray

It could be. If it has a bad odor, then that's probably for sure.

Yes, cut off the leave below the infection and dab the wound with a q-tip dipped in cinnamon poweder (don't get any on the roots).

That is a systemic bacterial infection, so a topical treatment like Physan will have no effect on the infected plant. You'd do better with a copper-based treatment, since they are systemic.

Your advice is always appreciated, Ray!

Do you think the copper-based treatments one would find at a hardware store could work for something like this in a pinch? I’m not sure how much time I have left and I figured that acting fast by getting something locally may increase the odds of this surviving

[estación seca]

St Augustine Orchid Society: Diseases.

Yes, start with Bordeaux mixture if you can find it today. Spray your other plants. Unpot this plant and cut off everything infected. Sanitize the tool between cuts. 70% alcohol is adequate.

Address the cause. Erwinia is a disease of excessive temperature plus excessive humidity.

[Dimples]

Originally Posted by Ray

You'd do better with a copper-based treatment, since they are systemic.

Not to derail, but which copper based pesticides are systemic? All my reading says it’s primarily an effective topical preventative, with the ability to suppress mild cases of external disease (powdery mildew, etc.).

[greenhouseFrog]

Originally Posted by estación seca

St Augustine Orchid Society: Diseases.

Yes, start with Bordeaux mixture if you can find it today. Spray your other plants. Unpot this plant and cut off everything infected. Sanitize the tool between cuts. 70% alcohol is adequate.

Address the cause. Erwinia is a disease of excessive temperature plus excessive humidity.

Thank you, ES—that article from St. Augustine was great! I cringed a bit more every time I scrolled further while looking at the pictures because I feel like I recognized a lot of them, but I’ll jump off those bridges when I get to em’

I’m familiar with Bordeaux mix although I must admit that I have stayed away from it in the past due to the number of bromeliads in the landscape, but I can definitely spray down the containerized plants and the mounted ones that can still be moved around!

I think I have an idea of what caused this and need to move stuff around—thanks again, ES!

[greenhouseFrog]

Originally Posted by Dimples

Not to derail, but which copper based pesticides are systemic? All my reading says it’s primarily an effective topical preventative, with the ability to suppress mild cases of external disease (powdery mildew, etc.).

Hey Dimples, I don’t mean to derail either, but I was under the same impression as well when it came to copper-based fungicides/bactericide, that they were “contact-only”, so to speak. While I was taking a closer look, it seemed like there are systemic copper products; Phyton-27(or 24, or 35)being some that I’ve seen while reading or heard mentioned in conversation.

The manufacturers advertise Phyton-27(and the others) as systemic, but I could not confirm through the product literature whether or not it had the ability to be absorbed through foliage—the instructions say it “may be applied by spray, drench, dip, or injection”, but there is no information explicitly stating its action as locally systemic, xylem mobile, or amphimobile, etc.

From what I can gather from the product label, it seems that, like Bordeaux mixture, copper sulfate pentahydrate is our source of copper in Phyton, but with some additions, namely ammonium formate and sodium laureth sulfate. The patent for the formulation reads in part “…composed essentially of a tannate complex of cupric ammonium formate in an aqueous solution combined with a surfactant to prevent precipitation and may include a buffer to enable its use in native waters.” That’s pretty much Greek to me, but it was as far as I got before throwing in the towel

[estación seca]

Are you having an early hot spell? As far south as you are, these might be better as windowsill house plants during warm weather.

Edit: Frog mentioned worrying about the bromeliads. Almost the entire family Bromeliaceae is highly sensitive to copper in any form: Aechmea, Billbergia, Dyckia, Guzmania, Hechtia, Tillandsia, Vriesia, all your favorites. Even small amounts will kill them. Bromeliad enthusiasts use fertilizers without copper. If you've had trouble with bromeliads before, maybe this was the problem.

One surprising exception is the pineapple, Ananas comosus, which doesn't care about copper.

[greenhouseFrog]

Originally Posted by estación seca

Are you having an early hot spell? As far south as you are, these might be better as windowsill house plants during warm weather.

Highs peak mid to upper 80’s F by the end of February where I’m at. This year it’s been a little nicer with fronts still cooling us down a bit in March, but it was 91F today in the shade on the porch where this thing lives. It’s 11PM and it’s 77F outside now.

If I’m being honest with myself, I feel like the Oncidiums are taking up a lot of prime space on the porch that might be better occupied by something else…like some Cattleya purpuratas

[Ray]

Any copper-based treatment is systemic.