BLC Ports of Paradise issue - need disease ID help

[smokinjoe1952]

Home temperature range from 68-75F outside the grow chamber.

Humidity can drop as low as 20-25% if it is really cold outside and I can't run the whole house humidifier higher without getting condensation on the windows. Today the humidity is about 35% in the house.

My problem is that we live in a house that is surrounded by trees, so getting light in is a problem. That is one of the reasons I wanted the chamber. It has been up and running since last spring, and this is the only disease I have had, so probably not time to panic.

I do know the Phals really like the higher humidity, but maybe 77-80% at night is too much.

My humidifier tray fan is off now, and the lights have been off for several hours.

Current CHAMBER readings at midnight are: 68F and 67% humidity. It looks like shutting off the humidity tray fan takes it down from 77% to 68%.

So will Phals and Catts. ( and oncs. and Phaphs and Phrags be happy with that humidity?

I do have 2 shelves with independent dimmable LED lighting, so all plans get the same environment EXCEPT for the light levels on the 2 shelves.

[Fernando]

I don't think there is too much RH, as long as there is no water condensing during the nights and dripping on the plants, 80% is very OK.

I'd focus on the growing cycle: half grown until not mature pseudobulbs are very vulnerable. I know my plants and which of them are prone to black rot. These I don't feed at all during this stage. Once the pseudobulb has emerged from the upmost husk (the lesser ones already dry), and begins to harden, only then I begin feeding.
Perhaps it has someting to do with the rooting-type of the Cattleyas, but as I don't have so much variety, I can't tell.

[smokinjoe1952]

No condensation whatsoever. I'll reduce or eliminate fertilizer when the sb's are in their adolescent phase, although I don't think I have read about that particular strategy.

I assume you would run the humidity fan 24/7 and allow the RH to rise to the 77-80% range in the evening.

Is that a correct assumption?

SJ

[Sharon's Sheepdogs]

I agree with the previous posts that your orchid is most likely suffering from Black Rot. I am not sure where you live but you will see Black Rot appear when night time temperatures drop and your humidity levels are high.

Personally, I believe your RH is too high. If the disease occurred after you increased your night time humidity, that probably caused it. These fungus' are already on your orchids but do not multiply until the right conditions present themselves.

I grow primarily Cattleyas and Phalaenopsis. I never let my night time humidity go above 65 degrees. I have not had any problems with growing & blooming at that humidity level. I keep my daytime humidity between 50 & 55 degrees. I read an article from a professional orchid grower that this level of humidity is fine for growing orchids. However, I am not experienced enough to say whether that level of humidity is sufficient in growing paphs & phrags.

Back to Black Rot. This fungus is actually a 'water mould.' The fungus is an organism known as an 'oomycete' which transports itself in water. Once it has developed on one plant, it infects your other plants by splashing water when you are watering.

I use a preventative spray program for these types of diseases because it is a more affordable way to control them. The cost of Subdue and Alliette are very expensive. I believe the cost of Truban is close to $100.00. So, every three months I water my plants with systemics, Banrot (you can purchase a small container from Green Barn Orchid Supply) and Agrifos (must have a pH of 6.5 when applied). I have had very little problem with plant diseases once I started this program.

However, you cannot use the same fungicides twice in a row, they must be rotated or the fungus will develop a resistance. I had higher incidences of fungus problems when I grew my orchids hydroponically. I have been much more successful growing in bark. I have an indoor set up in my basement. If you are interested in knowing how I do this, send me a separate message.

Whenever I see a disease develop, I cut it back using sterile razor blades to healthy growth. I then pour peroxide on it for several seconds and dust with Sulphur. I will do these for the next two to three days. Then I watch the cut to see if the disease begins developing again.

Also, if you are interested in learning more about Black Rot, you might want to to read the following articles:

The Ruinous Rots
http://staugorchidsociety.org/PDF/AOS15-Diseases1.pdf

Damping-off
Damping-off Diseases

Sorry this is so long but I do hope it helped. Good luck!

[smokinjoe1952]

Sharon,

Thanks for the great information and the source of a reasonable amount of Banrot. I am committed to sh right now, but will try the Banrot once a month on at least the Catts.

SJ