Dendrobium spectabile leaves yellowing and dropping

[Luke]

Hello, I am a newby. I live in Ft Lauderdale and have a collection of about 80 orchids. I’ve been a hobbyist for about 12 yrs. I have this large dendrobium spectabile that started blooming with about 8 blooms, then many leaves started to yellow and fall off. It mostly happens with a pair of leaves on the same pseudobulb at the same time. The newest growth is less affected. There are a lot of marks on the underside of some of the older leaves, but they feel smooth(photo). These leaves are mottled on the top ( photo)New leaves are also dropping( photo of top and bottom of leaf pair). I’ve treated it with thiomyl and orthene. Not ideal, but I am being aggressive. Any help is greatly appreciated. Thanks!

[estación seca]

Welcome to the Orchid Board, Luke!

Is it growing outside? This is a warmth-loving plant, and Florida has had unseasonably cold weather recently. That could account for exactly what you're seeing.

[Luke]

Thanks for the response. It is normally outside, but I brought it into the house about 3 weeks ago to see it bloom. That was before the cold weather. we didn’t let it get below 72 in the house. This problem started about a week ago. Is this plant that sensitive to changes in environment?

[Roberta]

Sudden drop in the humidity maybe?

[OrchidSIlove2]

Hi Luke! I live in Ft. Lauderdale and have about as many orchids as you do as well. Hobby grower. I’m having terrible trouble with my den spec. I purchased about 3 years ago full of blooms. It was growing fine except no more new canes. Now the leaves are yellowing and falling and I’m in a panic! Any ideas?

[Dusty Ol' Man]

Not something I grow, but I found this:
Travaldo's blog: Dendrobium spectabile care and culture

[OrchidSIlove2]

Thank you ! I have seen this site and I’m growing it exactly as it says.

[Keysguy]

Luke- You said you moved it into the house and it's 72.
If there were no yellow leaves when you brought it in and you have AC running, my suspicion is that it will HATE that environment.

I move mine to the screen porch when they are in bloom so it is essentially outside. My spectabile was on the porch for almost 4 months in bloom this past winter and spring. Another thing to consider is your house water quality vs the rainwater it was used to.

You just need to be mindful that moving an outdoor plant indoors for any length of time without considering these environmental changes could have serious consequences. I'd put it back where is was outside and if it's going to get below 55-60 bring it in just until the weather warms back up.
In FLL that can be outside 95% of the year.