Gray mold on Phalaenopsis flowers. Please help - Orchid Board

circlemon · #1 06-21-2022, 02:23 PM

Hello all! I'm new to the forum, but have had orchids awhile. This is the first time I've experienced anything like this. First and alarmingly, I had new buds fall off this plant. It "re-bloomed" on the same spike rather quickly. But days after the new blooms opened, they are falling off and look moldy. Pictures attached. Any idea on what's the issue and remedy?
It's been in the same location/watering routine for years. None of the other orchids in the same vicinity seem affected.

estación seca · #2 06-21-2022, 11:13 PM

Welcome to the Orchid Board.

It looks like mildew or botrytis blight. But these are normally diseases of cool temperatures, with dry or wet air, respectively. What are your growing conditions? Temperatures day/night, relative humidity? How are you watering and how often?

circlemon · #3 06-22-2022, 01:10 PM

I am in Illinois, USA. So it's summer and relatively hot and somewhat humid. But they are indoors by a window, where it is kept in the low 70s. I water about 1 time a week.
I have 6 other orchids in close proximity (so same environment and same water schedule) and none are affected so far.
I have isolated the sick one. Any advice?

estación seca · #4 06-22-2022, 02:59 PM

I'm going to guess it's mildew. The spores are everywhere so prevention is the key. I get it on roses here in spring. Fungicides do kill it but the spores are everywhere. Non-chemical control works fine.

If you can put your Phals outside in full shade they would greatly prefer the heat and humidity over your cool home. Mildew doesn't grow well in higher temperatures. Phals love temperatures in the 80s F.

You can also use a water spray in the shower or sink to knock spores off the plants.

I would cut off the flowers and dispose of them. If that's mildew the grey patches are spore bodies.

circlemon · #5 06-22-2022, 03:15 PM

Thank you. I keep them at my office, so outside isn't an option really. I've had them in the same spot for maybe 5 years, no issue. They seem to thrive. I'll do as you suggest and cut the blooms off and hope that's the end of it. I appreciate your input.