Help! Tan Splotches on Healthy Cattleya
 

My Cattleya mossiae (‘Blanca’ x Aurora’) suddenly developed large tan splotches on top surface of two most mature leaves. There are no yellow halos around the splotches. They are recessed. Bottom of leaves are fine.

I bought the plant two months ago (mail order from Hausermann’s) and repotted it immediately. It has thrived, putting on an excellent new growth.

LIGHTING: Tip of top leaf is 6” from T8 full spectrum LED light strip (along with 20 other Cattleyas that are NOT splotched), 6 hours per day, plus little light from East window.

FERT/WATER: Very weak 'Better-Gro Orchid Plus' (1/4 teaspoon per gallon), mixed with few drops of CalMag and a few drops of seaweed extract – about once a week.

MEDIUM: Cattleya orchid mix from Repotme. Root tips are beginning to appear around the see-through plastic pot.

TEMP: In grow room with exterior door and windows open to Alabama heat and humidity.

The splotches occurred quickly (within two days) and do not appear on any nearby Cattleyas.

Please help me figure out what this is and what I can do. I searched the web for pictures, but found none that looked exactly like this. Thanks so much!!!

Looks like the damaged region is drying out ROBB, which is a good sign.

Maybe just monitor the temperature - or the rates of change in temperature. Maybe if the temperature in some leaves get too high, or if the change in temperature is too fast from one temperature to another much different temperature, then cells in the leaves could bust.

But not sure what it is due to at the moment!

Thanks, SouthPark. The "leaves could bust", ouch! I have it isolated for now -- on my kitchen counter. I am so very new to orchids, and panic when something strange like this shows up. Thanks to OB, I have a place to go for advice.

Most welcome ROBB! From the look of that leaf ------ as much as it looks scary ----- those regions look as if they're drying (and that is good!).

Right now ---- the issue doesn't appear to be disease or insect-related or anything like that.

That is good news,SouthPark. I will monitor it closely. Should I slow down on water???

ROBB ----- you can still water the same way. That should be ok. And may be you have been doing it already ------ just water the media and roots only. Don't put water on the leaves, or at least not water having temperature significantly different than the leaf temperature.

Usually, if the temperature around the plant changes relatively slowly - gradually, then the cells of the leaves stay in good shape. But relatively large change in leaf temperature at relatively fast rate can possibly do the cell busting thing.

Although, the 'edema' effect I've seen in online photos are smaller in patches. But I recall seeing one pic in the past that looked similar in condition - where it was said to be heat stress. But I'm pretty sure that your growing area doesn't get to that sort of high temperature! So thinking more like temperature change effect maybe.

It looks like they got “munched”. Any chance you have snails, slugs, or caterpillars of some type around?

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Thanks, aliceinwl. The orchid cannot be reached by munchers. It is inside on third shelf up. Also, no other Cattleyas sitting just inches away have no splotches. Do you have any other ideas? I am at my wits end!