Buds blasting on Mormodes x Cycnoches hybrid
 

These spikes have been going like gangbusters for weeks. In the last 10 days or so, though, the top spike has dropped 4 buds and a couple more are turning yellow now.

Anyone know the humidity requirements of this group when dormant, but in spike?

Or have other ideas about the likeliest culprits for the bud blast?

Thanks!

Cold, or drafts, or any sudden change in environment can cause bud blast and that, rather than humidity, would be my first guess.

I had 2 spikes that had a bloom on each blast at exactly the same spot on the stem - about half way down. I don't know why. If you aren't misting the spikes, storing apples nearby, using candles or the fireplace.... or turning the plant, your guess is as good as mine..

I can rule out misting, storing apples, using candles, fireplace, or turning the plant. Also drafts and significant changes in conditions. (thank you both for the possibilities)

I checked with Fred at SVO and he asked if I'd seen any thrips in my growing area. I haven't, but the Cattleya that's nearest the Mormodes has girdled roots. So there's maybe reason for suspicion.