Black spots and yellowing leaves falling off on mystery orchid

[MrK_13]

Hello! I am new to the forum and to orchid growing in general. I received this orchid as a gift last Father's day and the pot just said orchid spp. It did great over the summer and even started putting out the new growth on the left you see next to the pseudobulb. Around November it started getting these spots and then the leaves would yellow and fall off. It did this for a bit and I thought maybe I was overwatering so I held back and that seemed to have slowed or stopped the progression. So two questions, what kind of orchid am I dealing with and is this a cultural issue or am I dealing with a fungus? I think it might be a brassia from what I have found online.
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[Roberta]

First, Welcome!
It looks like an Oncidium-tribe hybrid (which would include Brassia). I doubt that it's a species. This whole group hates to dry out. So if the mix is chunky, it needs to be watered pretty often. If it did well in summer, it may want to be on the warmer than it currently is. What are your temperatures? Also... have you repotted it? If not, likely a good idea - as spring approaches, new growth will start and that's the time to pot. Does that pot have drainage? If not, roots in the pot may have rotted. At any rate, the fact that many of the roots are outside of the pot indicates that the conditions in the pot aren't great

Looking at the last photo, I wonder if there might be a spider mite issue They are very tiny (almost microscopic), thrive in dry conditions especially if there isn't a lot of air movenent, and hide on the back sides of thin-leaved plants.

[MrK_13]

Thank you! I don't see any spider mites. I did wipe the leaves to be sure and moved it to my ikea cabinet greenhouse that has a fan in it. The humidity in there usually cures any spider mite issues I've had with other plants. It was in the original plastic container before with sphagnum moss and I recently repotted to the chunkier mix thinking it was a water issue at first, and to accommodate the new growth as it was moving outwards. The new pot does have drainage and my temps are usually around 68-70 degrees Fahrenheit and stay pretty consistent, but it might have been too close to the windows and got cold that way. It was pretty root-bound in the original container and I did my best to fit them all in the new pot without upsizing too much.

[Roberta]

Hopefully, new growth will be along shortly. That leads to new roots. (Even under the best of circumstances, these tend to "cannibalize" the old growth to support the new, so old pseudobulbs shrivel and old leaves drop. ) The chunky mix likely will be OK, but you'll need to water more frequently - water well, so it runs through the pot (which pulls air into the root zone and also flushes out "crud".

[estación seca]

Welcome! The newest growth had roots out in the air. Oncidium intergeneric hybrids don't like drying out at all. I think it wasn't getting enough water. Ideally you should repot them when new growths are just beginning to form roots, and don't let Oncs. crawl out of pots. Cattleyas do fine crawling out of pots if it's humid enough.

[MrK_13]

Thanks for the replies! So I repotted it into a new pot this morning. I teased out the roots with a wooden stick and removed all the old media. The bark was pretty degraded and the plant was very root-bound. I adjusted it a bit and was able to fit the new growth with roots into this pot while still having it be a snug fit. There were some old pseudobulbs that were rotted in the bottom so I removed those. All the roots looked pretty good and no funky smell so I am hoping now that it is in a new pot with all new medium it will start to bounce back. I will keep an eye on watering but for me personally I have killed more plants from overwatering than underwatering so I will keep an eye on moisture until I get a rhythm down. Thanks again everyone for the responses!