Oncidium leaves changing colour. Please help!

[Hansu.nahar]

Hello,

A couple of months back my beautiful sharry baby started producing a flower spike. However, in the past 1 week, the leaves as well as the pseudobulbs started developing yellow spots and now, the flower spike seems to be browning. Could you please help me identify the problem and propose some solutions?

Thanks in advance.

[estación seca]

This looks to me like some kind of fungal or viral disease. Is your relative humidity high this time of year? Could you take it to a nearby university with an agricultural department? Sometimes they can identify pathogens.

[Hansu.nahar]

Originally Posted by estación seca

This looks to me like some kind of fungal or viral disease. Is your relative humidity high this time of year? Could you take it to a nearby university with an agricultural department? Sometimes they can identify pathogens.

The current humidity is pretty low in my city atm. About 10% (though I do spray the plants thrice everyday after which the RH rises up to 80% + for an hour or so).

Its blazing hot too. Currently 43 C.

[cjm3fl]

Is there any possibility that the plant is receiving direct sunlight during any part of the day?

While I agree with estación seca that there is a fungal or disease issue, some of the yellowing spots resemble burning spots I've noticed on a leaf or two here on one of my oncidiums.


Just an additional consideration.

[campchi]

Ok, i think those marks might be sun burn since you did mention about spraying twice a day. Depending what time of the day you spray your plants, if there's any water reside on the leave around noon time, it will super heat up and burn the leaves. Might wanna move it to an area with less light, or get a shade clothes.

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[estación seca]

It's a longstanding myth that sun shining on water droplets will burn leaves. The water will not rise above the temperature of the leaf. As it evaporates it will cool the leaves.

Hansu.nahar wrote the ambient temperatures are 43C / 110 F and relative humidity 10%. Under those conditions, leaves will be dry within 5 minutes of misting.

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[cjm3fl]

Originally Posted by estación seca

It's a longstanding myth that sun shining on water droplets will burn leaves.

Maybe where you are, my friend, but it's a huge concern here in central, and southern Florida.
I've seen pasty-white tourist burn to a crisp in 20 minutes. And burn marks on thin leafed plants and orchids, plus various plant blooms, because they were watered in the sun.


I've had to move my Phal's from the back of the house (easterly exposure) because the golf course started watering in the mornings and 80% of my blooms got heavy burn spots from just the morning sun.
With the thick leaves of the Phal's it's not as much of an issue as it would be for Ocnidiums, but there are some scorch marks and burn spots on the leaves of my Phal's.


Water is a known magnifier around here and Florida gardeners are instructed when not to water (later morning through early evening) when plants are exposed to the sun.

The high humidity down here also increases the time it takes for evaporation.

In "dry heat" areas it might not be much of an issue.
But as a blanket-rule, it could be misleading.

[rbarata]

Hansu.nahar wrote the ambient temperatures are 43C / 110 F and relative humidity 10%. Under those conditions, leaves will be dry within 5 minutes of misting.

Yes, that's what I thought too. Misting is not the way to go. I belive a water tray, although probably not enough, would be more effective.

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[Optimist]

You may need to train a fan on it to cool it down. Sadly most intermediate orchids cannot deal with 110F degrees, and 10% humidity. It is usually at least 30% humidity and 80F degrees tops.

Since oncidiums can take indoor window light, maybe you should tent it to raise the humidity, and use an ultrasonic humidifier and a fan. That will cool down the area and raise the humidity.

Fish tanks also raise humidity in enclosed rooms. (Just don't put the fish tank directly in the sunny window).

It depends on what resources you have available.

[rbarata]

I grow oncidiums with temps around low 80's (28 C) and % between 10 to 20. But I have them faced north and I'm always vigilant about medium dryness.