Fungus or paranoia?

Hi all,

Just recently discovered this forum and am very impressed with the amount of knowledge and helpfulness out there. I'm in need of a "second opinion" and am hoping someone can help me out.

I have a new Oncidium purchased from a local orchid greenhouse a few days ago. I didn't notice when I purchased it (probably because I didn't know to look for it!) whether the leaves had black spots on them at the time, but they definitely have them now and I am convinced they are growing/spreading. They are mostly on the older growth leaves, although some of the newer growth has them too but to a lesser extent. A couple leaves have it concentrated at the tip (like in the attached picture), others have it along the full length of the leaf (although with those it seems different - more mottled and consistent along the entire leaf -- not so much concentrated in one area). In neither case do the spots feel bumpy or raised. The leaves with spots more concentrated at the tip do show some yellowing/browning but the others don't (at least not yet!).

Looking around online, I get the impression this is a fairly common issue with Oncidiums and fungus, and that I should be cutting off the affected areas and treating the whole plant with a fungicide. I called the greenhouse to get their opinion, and the folks there agreed it was common, but seemed to think it was not fungal but rather a matter of malnourishment. They suggested I should just keep up the regular watering/feeding regimen and cut off the affected leaves, but recommended against treating with the fungicide. This seemed odd to me because "malnourishment" seems to imply that they're not taking proper care of the plants (since I just purchased it this past weekend, I don't think I've had enough time to cause this much damage!). But perhaps I just wasn't describing the symptoms very well, or maybe the plant is big enough that it is in fact favoring the new growth and starving the old (this seems like a fairly sizeable plant, it's in a 6" pot and has two flower spikes). Taking it back to the greenhouse so they can see it in person is an option, but not until the weekend.

Sorry for the wordy post. I'd appreciate any/all opinions or suggestions.

Thanks much,

Jon

Attached Images

 

Hi Jon,

Don't worry about that. On oncidiums that get enough light to bloom, you will see 'sunspots'. It is normal and if your foliage was pretty (without spots) your oncidium probably would not bloom because it is not getting enough sunlight.

The brown tip of the leaf might be a bit of fertilizer burn. This is caused by salt build-up in the orchid medium. If you have not already done so, flush the pot out with clear water. Just run water through the pot for a few minutes. If you are feeling adventurous, I recommend repotting your orchid. )I always try to repot all new orchids. It is a matter of safety for my other plants as well as to let me see how the roots look and if I need to do anything special.)

Nice to have you join us. Enjoy the forum.

Cheers,
BD

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We could learn a lot from crayons: some are sharp, some are pretty, some are dull, some have weird names, and all are different colors....but they all exist very nicely in the same box. ...Hmmm? .

Really, nothing to worry about. Oncidiums are generally ratty plants when grown properly. The old orchid adage goes: "If you grow, dark beautiful green foliage then all you will grow is dark beautiful green foliage."

These spots are a form of secondary fungal infection, but they're really VERY common on just about every blooming oncid I've seen.

So I guess it's Paranoia 2, Fungus 0. I'll go with that.

I do have a couple follow on questions though:

-- How does one differentiate between this "normal" spotting and a true needs-to-be-treated-immediately fungus?

-- Should I be doing regular "preventive" fungicide treatments, as I've seen suggested in other places?

Thanks,

Jon

When you get a bad fungal infection, it usually attacks the pseudobulbs first on the oncidiums (I've noticed). However, if the fungal marks progress rapidly down the leaves, I would treat the plant to be on the safe side.

As far as preventative treatments, water your plants once a month with Physan or a like product. (Follow label instructions.)

Sounds good, thanks much for the info and reassurance!

Jon