Thursday, October 2, 2008

Question for the Hive Mind: Phalaenopsis spots

This isn't actually a problem specific to the Phalaenopsis, but this is the most dramatic and visible example I could find:

For some reason, most of the flowering orchids we had a few weeks ago all developed spots simultaneously. The orchids were Phalaenopsis, mostly, but the same thing also happened with a couple of Dendrobiums and a Spathoglottis. Most of the plants in question had been outside at the time. There'd been some rain, and some cooler temperatures, but nothing crazy; we'd had the same plants outside last year at this time, down to about 40ºF / 4ºC, and nothing like this happened to them (though they were also not flowering at the time, by and large).

The Spathoglottis had only just arrived, and it was never outside at any point: it was in the greenhouse for a couple days and then went into the store.

Only the largest spots are on both the front and back of the petal. Whatever it is, it's something that is specifically damaging only the fronts of the flowers.

Nobody at work has seen anything like it. We're not exactly worried about it happening again, but we'd like to have some idea what the hell it was. Anybody?


Frances said...

Hi Mr. Sub, no expert here, but I do grow orchids and those spots look like overspray of some kind to me, especially since they are only on the fronts. That's all I got.


Wicked Gardener said...

I had something similar on mine earlier in the year, but the color had a more orange tinge.

sheila said...

Hi mr s, I've been on hiatus from blog reading for a while, but saw the phal photo. My phalaenopsis book talks about botrytis on flowers, occuring most commonly in cool, damp and low-light conditions in greenhouse culture, especially if humidity goes above 65%. It will not harm the plant but ruins the blooms. In very early stages, it can be stopped by spraying affected flowers with a general purpose antiseptic like Physan. Here is a link to a photo of an orchid with botrytis (not a phal):

Sure looks similar to me.

sheila said...

oops, the end of that url is


RebelCowgirl said...

Since I have no real way to know exact which parts of the plant are affected other than the flowers I can only make a few guesses as to the cause. 1) Fungal - If this is the case then reducing the amount of watering and misting the plants are receiving will help reduce this. 2) Spider Mites 3) Disease - in which isolation and ultimate killing of the plant once disease is confirmed is the only answer.

My guess is this is an issue with moisture and/or humidity. In which everything I've read suggests moving the plants to a warmer less humid environment, increase the amount of light, increase aeration (orchids like to have a lot of air movement), skip a watering or two, and treat for fungal. If this does not help and the problem persist. You may have a Spider or other mite invasion or worse a disease spreading to all plants infected. Either way, I would definitely isolate all infect plants to keep any new arrivals in a completely different area so as not to become infected. You could also try treating with a copper based fungicide/insecticide. If the problem persists try contacting your local Agriculture Dept. Branch or an orchid specialist. I found quite a bit of information by visiting this website and it may help you as well:

Hope things get or have cleared up.