Oncidium turned yellow and shriveled up

[solstice]

Hello,

After much lurking I was prompted to finally join this forum and create a post because one of my Oncidiums turned yellow and shriveled up over the course of a week.

It' a relatively young Onc. Space Race and was potted in bark. The bulbs took on a really unhealthy yellow tint, lost all their shape and became quite mushy to the touch. Roots seem okay but slightly dessicated. I can't tell if that's because of the potting media as I watered it regularly every few days.

I'm not sure if the attached photos are visible as this is my first post. Google hasn't been of much help and I'm hoping to avoid this spreading to my other oncidiums.

[estación seca]

Welcome to the Orchid Board!

What is the temperature and relative humidity in your growing area? What kind of light, and how much was it getting? How big was the pot? It looks to me like it got cooked. Any chance it was in direct sunlight?

[solstice]

Thank you!

I live in a classic NYC walk up apartment so the conditions are a bit on the dry side (esp. with the AC running now that summer's here). Day time temps hover at about 75-80 and in the night with the AC it's 70.

The funny thing is it's not under any direct light, I've set it on a shelf about 5 feet away from a south facing window so it's bright without ever getting hit by direct sunlight. I've got some other orchids on the shelf (a Sharry Baby and a Dendrobium) and they're both doing just fine.

[estación seca]

I am puzzled. Usually when Oncidiums rot from the roots not getting air, they turn brown or black from the base up, and the roots are dark brown and slimy. If they are struggling with insufficient water, the leaves drop prematurely and the pseudobulbs shrivel. Maybe somebody else has an idea.

[SouthPark]

Is the air-con running all of the time? And is there gentle air-movement in the growing area a lot of the time?

And are the other orchids potted in exactly the same way as this one?

Also - for watering, does any water stay on or in the base/bottom of the stem region for long periods of time?

Maybe could just monitor the temperature (somehow) through-out the whole day - every day.

Also - just in case - in any case - if roots and media are wet for overly-long, then try to avoid too wet for too long. Just in case. As that could possibly make leaves yellow too - where the roots may still look ok for a while, but can get taken out too, after the leaves and bulbs deteriorate.

How long roughly has/had this oncidium been growing there in that spot?

[Ray]

Wow! Two in one session (Tricho tigrinum thread being the other).

Looks like an erwinia infection, based only upon the discoloration and mushiness. It is spread really easily via water.

That's surely a goner, but I'd lean toward a treatment with a copper compound if caught early enough.

[DrDawn]

Originally Posted by solstice

I live in a classic NYC walk up apartment so the conditions are a bit on the dry side (esp. with the AC running now that summer's here). Day time temps hover at about 75-80 and in the night with the AC it's 70.

Threadjack:
FYI, in Boston with an AC blasting 14-16hrs/day in my orchid room (aka living room), the humidity in the past month has averaged 58% (with absolute minimum of 43%). So, having an AC doesn't guarantee that there's low relative humidity. I really like this cheap sensor from Amazon to keep track of the actual growing conditions.

[solstice]

Originally Posted by Ray

Wow! Two in one session (Tricho tigrinum thread being the other).

Looks like an erwinia infection, based only upon the discoloration and mushiness. It is spread really easily via water.

That's surely a goner, but I'd lean toward a treatment with a copper compound if caught early enough.

I believe this is it! After some googling I do think it's an Erwinia infection. I did away with the plant as it was too far gone.

And thanks everyone for your replies, I don't run my AC all day and sometimes let the hot humid summer air in through the windows. I also run the fan setting on the AC to just have air movement without cooling but alas. I suspect the sudden onset of equatorial humidity in NY these past few weeks might be to blame. I really need to invest in a humidity and temp measure so thanks for the recommendation!

[DrDawn]

Good luck! I hope the rest of your plants are unaffected. Yes, the East Coast has turned quite tropical recently, almost like a rainforest. :-P

[SouthPark]

I agree with trying copper spray for future cases. Watching the orchid like a hawk and treating the condition early enough can significantly increase chances of survival. Also consider getting (for the medical kit) monterey garden phos.