Rotting Oncidium sharry baby

[Oranagra]

Hi,
I recently moved my Oncidium sharry baby to semi-hydro, as it needed repotting (overgrown it's pot), and didn't seem to do good in it's previous bark mix setup, the pseudo bulbs were quite thin and shrunk, but there were new growths, and no rotting.

now, a few months later, the back bulbs started rotting one by one.. at first i removed the rotted bulbs, but now when more and more are rotting, i tried to to cut it and try to save the healthy portions, and throw the rest to the trash.

while cutting i noticed a purple ring on the rhizome, which i remember reading that it might be a sign of a virus.

besides that, i have some black spots on the bulbs, and on the leaves, i think i had spider mites, but not a severe outbreak.

[emmajs243]

To me, the purple band looks exactly like what they show for Fusariam sp. Now, I have no experience with Fusariam and am still just a beginner overall so do know, this is just me doing a picture comparison from what I have seen when researching possible diagnosis for some of my rescue orchids. I just saw that nobody had responded to you and figured I would share what I have! Which isn't too much but! I finally found this wonderful link that I will share, it was extremely educational for me. The top portion is all about pests but if you keep going down it will get into diseases, viruses, fungus, everything for orchids. It shows a picture that looks nearly identical of yours for Fusariam sp. I do hope I am wrong but take a look at the link to help build your own opinion! Like I said, I am new to all of this so don't take my opinion worth much! I more so just wanted to share the link! Hopefully some orchid experts will chime in here!

http://www.phelpsfarm.com/OrchidPestsandDiseases.pdf

[Roberta]

Roots look decent, and it appears that there's a new one starting. Would not worry about the black dots... there may be a bit of fungal or bacterial problem. Some shriveling of the pseudobulbs is pretty common. Keep isolated from other plants. And DON'T use peroxide on roots! Would doubt fusarium... seems mostly to be an affliction of those who watch Miss Orchid Girl videos, actually very uncommon outside of tropical areas. could be a different bacterial or fungal issue. But it if were my plant I would not be concerned. Maybe dust the cut with cinnamon (but not the roots!)

To check for spider mites (symptom is whitish stippling on bottom side of leaves) wipe with a tissue soaked in alcohol. If you see reddish deposit, then probably. There is no "minor" spider mite infestation, if it is there it needs to be treated (soapy water sprayed on leaves, repeated at 5 day to 1 week intervals for several weeks or a month - or more, to kill successive generations. But the black spots are not spider mite symptoms.

[emmajs243]

There is an expert! Definitely listen to Roberta! I mean, the link is still super educational and one of the best ones I have found about orchid pests and diseases BUT! I would trust someone with experience a lot more then photo comparison!

Roberta, may I ask, why do you recommend not spraying hydrogen peroxide? Just in the past day or two I have come to learn there is a huge debate on whether or not to use hydrogen peroxide on orchid roots. When you read (or watch youtube videos) it seems like EVERYONE is using hydrogen peroxide but when you really start talking to experienced growers like on here, there are many that do not recommend it. I would love to hear your reasoning in an effort to better make my own stance on the subject!

[Roberta]

Roots - especially the growing tips - have microscopic hairs that are damaged by peroxide. (If you have broken skin - which has large surface area - the peroxide will fizz and oxidize those rough surfaces. ) If you do it to those little root hairs, you are destroying an important working part of the root. So just wash off the roots, pull off what's rotted but don't rush to cut, and handle gently.

Even if the outside of the root (the velamen) is rotted, if the inside part (sort of stringy) is firm, it can hydrate the plant, and also serve to anchor it. The velamen is a sponge that stores water, and on a good root it will be green when wet or silvery if dry, but even a root without that can help the plant (especially if there aren't better ones) so rather than cutting I prefer to just give a sharp tug.. if totally no good it will break off.

[Oranagra]

thanks you all.
i already lost 5 bulbs, so when i saw that i keep loosing more and more of them, i decided to try to save some by cutting the healthy ones from the rest (and by doing so, lost the majority of the root mass).

I did also use Poroxide and Cinnamon, but i'm taking that new advise about Poroxide with me for future repottings.

so for now, i'll ignore the purple ring, keep these cuttings isolated and cutting tools sterilized, and hope they'll survive.

i'll check again for spider mites.. i thought that these black spots might be their aftermath.

last time when i suspected spider mites, they were especially on my Catasetum, and Oncidiums, so although these plants were next to other plants, i treated only the ones on which i saw the signs.
I used Paraffin oil at 1%, with a bit of dish soap, and it seemed to work (with only 2 treatments).

p.s. i had a Dendrobium with severe scale insect infestation that i couldn't get rid of, and that Paraffin treatment eliminated them easily.

[emmajs243]

I really hope your plant pulls through! And I have seen quite a few plants with those same little black dots and always was unsure what it might be. Good to know spider mites may be the culprit! Also, thank you so much for sharing about the Paraffin oil! Definitely will have to remember that one!