water pocketing and rot

[rymor]

Hey all-

I'm an outdoor grower and have run into an issue with a few of my cattleyas that have been rapidly growing during this time of year.

I have found that sometimes water gets trapped in the gap that the protective covering around an almost developed psuedobulb makes. I just had a set of buds rot out of the new growth due to this water collecting. A few months ago, the leaves of a bifoliate cattleya rotted out of the new growth due to the standing water in this protective coating.

I know air circulation and temp are important but I am outside. Does anyone have any cultural suggestions that I can make to negate this problem during times of extended rains/cool weather?

Thanks.

[Optimist]

Some people gently peel that off. Probably for the same reason. If you do not have that fast dry off time, then I can see it happening. In hot weather a good damp down in the morning followed by a day of drying out, and put them to bed dry. If you can.

The onion skin should really be stretching off after the bulb gets too big. Bursts through like the hulk. I've peeled a lot of mine off. It discolors and turns black. I think that is about all for "extended rain and cool weather."

Simply slitting it and peeling it down helps too. If it is dry, it can come off. (This may be controversial).

[Ray]

While I cannot guarantee 100% efficacy, I overhead watered my greenhouse for years, and saw some of the same issues, plus the added "bonus" of occasional crown rot in phals. That pretty much stopped once I had established a monthly routine of treatment with 1% Inocucor Garden Solution.

[Leafmite]

Someone who gardens once told me that milk helped prevent rotting issues. When I put the orchids outside, I found that adding a tablespoon of powdered milk to the watering can every time I watered seemed to put an end to the fungus issues. We sometimes had cool summers with rain every day for weeks on end and I would just give them a dose of the powdered milk every few days...no problems. Ray's solution sounds like a good one, too.

[rymor]

Thanks all for the insight. Just some mistakes that I must keep an eye out in the future.

What’s the view of a spray of physan during this damp, humid days? Would this help deter this sort of rotting out of maturing growths?

[Leafmite]

I have never used physan so I do not know. The only fungicide I have ever used is Captan but that was on my fruit trees and roses, not the orchids.

Good luck!

[Roberta]

Depending on how the growing area is set up, consider putting transparent polycarbonate panels under the shade cloth to keep cold rain off the plants. I did this over the area were I have the Catts (especially the species) hanging, and they have done very nicely through the winter (because cold and wet is a bad combination) Where I live, summer rain isn't a problem because we don't get any. But doing this, even chilly winter nights don't seem to be a problem. I have occasionally had buds rot where water collects at the base of the sheath, and I have found that creating drainage (with a razor blade, making a small hole in the "skin" surrounding the base of the leaf) does help.

[Ray]

Physan is a topical treatment only. Rotting occurs when the pathogens are inside the plant, so will be unaffected by the treatment.

physan, in my opinion, is best used as a treatment of the environment, reducing the pathogen population in the surrounding area, but that is useless and environmentally unsound outdoors.