Another Oncidium Black Spot Post

[SteveM]

Hey All,

OK the picture below is of my Bellaria that I got about a month ago. The thing is still in full bloom and all the leaves are looking very healthy, no leaf tip die back, no spotting on the main leaves. It is in my living room right now getting lows light and good air circulation. All the bracts of the pseudo bulbs have these black dots and have no yellow halo. I had these when I got the orchid. There was a lot so its hard to tell if it is spreading, I do not think so. they aren't getting any bigger anyways, I have sprayed with a copper fungicide, and with a systemic just today, about 2 weeks apart. They haven't responded to the copper treatment, did 2 treatments 2 weeks apart, and too early to see if terbuconazole is going to do anything. I really don't think its bacterial, I am doubting right now fungi, so its left with viral or mechanical or genetics or calcium deficiency. The weird thing is the leaves look beautiful, just the side bracts are affected. Picture is below. The psedo bulbs were severly dehydrated when I go it and they have been slowly getting better, Had another Allicearia with shriveled bulbs that took a few months to get the wrinkles out of them. Im planning on starting to fertilize with some calcium nitrate next week. Any ideas what these may be? Thanks all for all your help in the past, present and future.

[Roberta]

A lot of Oncidiums just do have ugly leaves. Here, whatever caused it, the spots will remain even if the cause is removed. So you can't depend on spots going away in evaluating treatment. In general, you shouldn't treat until you know what you're treating - different problems respond to different formulas. But I would suggest just leaving it alone. Don't worry about the spots unless and until you see the problem affecting new areas.

[SteveM]

Hey Roberta,
Thanks for your input as usual. In the past I have had black spots on my encylcia that were defeated (no more trace of them). And defeated black rot due to calcium defieciency in a cattleya seedling. Seedling grew 3 new shoots since last summer, and still has the same infected growth, but clean now. Both plants looks really great right now. I do think I caught both of them in the early stages, I think I posted this in the past last summer. Was really suspecting cercosporia on the encyclia. But I do think you are right, there are a lot on there that I don't think they will go away. Have to keep an eye on it, I am beginning to in-cooperate more calcium in my feeding anyways (clean city water) and working on making my own fertilizer formulaition, Made my own when I did hydroponics years ago. It probably will be a while until I am making 100 percent of it. (will practice on a few first LOL)

But I'm still kind of confused why these spots are contained in the side leaves and there seems to be a sharp delineation to where they start and are not there, Does not look like the typical sharry baby spots that I have seen on the others.