This is a question, not a reply. I'm new on the site and didn't see how to post a question. I recently bought a Bllra Marfitch 'Howard's Dream' and the underside of some of the leaves has black spots. The seller told me it arrived from his vendor in Hawaii that way and not to worry. While the orchid appears to need repotting, it looks otherwise pretty good - except for the spots. However, I looked around and am now worried that it may have a virus. I am a beginning grower but have about 20 orchids and don't want to infect others.

Now that I have copied your post to its own thread, it'll be easier for people to find/reply to you. :)

Oncidiums and related hybrids like yours tend to get spots very easily, and like the seller told you, normally there is no need to worry. If it's not spreading, then it should be fine. If you have some photos of it that would be a big help, it's much easier to say what it is that way.

Thank you for setting up a new thread for me. I'll post a picture tomorrow.

The only way to know if its a virus is by testing. But I think its fungi(notice the yellowing at the edges of the black markings on pic3) ...you can dab it with cotton dipped in physan20 and wet the leaves to absorb the antifungal because by the looks of it; the fungus is not just on the surface...
repeat it again the following week
you just have to wait till you have new clean healthy leaves...because these leaves are going to be spotted til they drop off...but you need these leaves even if they are contaminated to manufacture food for the plant

Evidently I posted the images to another thread, so here they are for this thread.

Bud - if the problem is a fungus, would you recommend cutting off the affected leaves? I'm reluctant to use anything toxic. There are 3 clean leaves on the left side of the plant in one of the images.

Thanks
pdeutsch

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Some of the oncidium type orchids are quite prone to spotting. It may have been in a humid greenhouse where it got a lot of overhead misting or watering and not a lot of room to breath. I would possibly consider taking off just the part of the leaf up to the last black mark on your 3rd picture as that looks a bit different than the spots. The other two spotted leaves are fairly heavily spotted, but I have similar spots on some of my orchids. Just keep an eye on them and try not to get the leaves wet and give them some moving air from a small fan. You could give them a dusting of sulfur powder which won't look that nice but might arrest anything that would spread. I did that to my zygopetalum and got it in a more open sunnier place and it quit getting spots. You could also try wiping the leaves with a cotton pad soaked in normal brown Listerine (yes the mouthwash but not the mint ones). It is anti-bacterial. I use that quite often and it doesn't hurt the leaves.

thats right silken...the regular mouthwash listerine...also a good home remedy antifungal...

Its really up to you if you want to cut the leaf thats really contaminated...as long as the plant will not suffer...its your call
if you do the antifungal it wont spread anymore...
water with room temp or tepid water from the sink...cold water on leaves will give you black spots too

Spots on Bllra Marfitch 'Howard's Dream'
 

Thanks all for help. I trimmed a few of the leaves from Howard's Dream that had the most spots and I wiped the other leaves with listerine.

I'll keep you posted.

pdeutsch