Dark Splotches on Healthy Phal. What is it?
 

I am a fairly new orchid hobbyist and need help identifying dark spots on an otherwise VERY healthy phal. The spots appeared over a couple of weeks, and are on both top and bottom of largest two leaves. Newest growth does not have the spots. The spots are not round but are more like splotches inside the leaves. Leaf surfaces (both topside and underside) are smooth. No yellow halos. Spots are not soft nor sunken and are not blisters. The plant has not been outside and is on a windowsill with 20 more phals that have no spots. All others are super healthy. The plant is not isolated, but if it is a virus it could have already spread to the other 20. Oh dear!!!!! I have searched this Board and the internet as a whole and cannot determine what is causing the splotches and what to do. (I have Agida test kit, but hate to cut one of the beautiful leaves.) The plant has gorgeous new roots and is in spike. Any help is appreciated.

Most likely beneficial to isolate this one - just in case. Good growing conditions? - good temperature, good air-circulation? Looks like your phals are growing nicely.

How long have you had this orchid for roughly?

A good idea to isolate the plant for now, and watch it like a hawk. Ensure good air circulation for all the roots and leaves. Avoid still-air environments.

My guess would be cold damage. I have a bunch of NOID complex hybrid Phalaenopsis and their tolerance (or lack of tolerance) for cold varies greatly between plants. If cold isn’t a possibility, sun damage would be my next guess. I’d try moving it to a warmer location or one without direct sun.

I purchased a Phalaenopsis with similar spotting this spring. The spots on mine progressed to sunken dry brown areas, but did not spread. New growth is unaffected. Unless you see the spots expanding despite “tweaking” growing conditions I wouldn’t worry about infection. If it does wind up being an infection, I think bacterial or fungal would be most likely.

Thanks, SouthPark. I have had the orchid for about a year and the growing conditions are excellent - East Window with excellent air movement. It bloomed about 9 months ago and has been extremely healthy since so I was surprised to see the splotches.

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Thanks AliceinWL. It is in the den (where we stay all the time) in a large East-facing window, so I don't think it is cold; however it could be sun damage. . . but would the splotches be black if it were sun damage?? I thought brown or yellow was sun damage. Also, would the splotches be on the backs of the leaves? I have isolated it and moved it away from the East window a bit.

Speaking of windows. All my 31 orchids are in front of very large East facing windows. (See Pic.) The windows are Marvins and have a very high E-Value. Not for this particular case of black splotches, but in general, do these high E-Value windows provide as much sun as others? Just curious about your expert opinion.

I LOVE, LOVE this orchid board. Since I am so new to orchids, it is my go-to place for every question. . . and i have soooo many. Merry Christmas and thanks for responding to my question.

Most welcome ROBB. Sounds good. Do you provide fertiliser and calcium-magnesium treatments? If the orchid isn't under attack by something, then could consider of a nutrient deficiency. At the moment, the cause is unknown - so it's ok to just have a think about various things related to the growing of it.

Regarding the air-movement, is that from open window all the time? Or there is a fan in the house that continues at all times of the day and night to move air gently around all the orchids?

nice view!!!

welcome-

I grow almost exclusively outside and i get all types of spot and splotches and marks on my plants....in general if the plant is healthy otherwise and the discoloration is not soft, mushy or weepy, they it is usually nothing.

i would do as others suggested and quarantine this fella for a while but unless you have recently added new plants or introduced some new element, it is unlikely for a spontaneous plant outbreak to occur

I will second what dirtycoconuts said.

The roots are looking healthy. Just keep an eye on it but as is nothing to worry about yet.

I will also agree that it could easily be a mild nutrient deficiency but I don't know your feeding regime or what water you use or if you adjust the ph for nutrients to be optimally available.

Just remember, although orchids need nutrients they need very little. It's a fine balance between not enough and too much. Also if it is nutrients there is no quick fix , just a bit of light fertilizing in future. And remember overfertilizing is 10 times worse than not feeding enough so do not try to overfeed to compensate...

If it is cold damage, I would expect to see a progression. When the damage initially occurs, it looks similar to the spots on your plant. Over the ensuing days and weeks, the damaged areas will blacken and collapse as the dead tissue degrades. Seeing how far back from the window your plants are, I think cold damage is less likely. It could just be a symptom of aging leaves.

Just as a back-up precaution, you could spray/mist some mancozeb onto the leaves of this orchid. Also, if it's not a pathogen effect, then google these words too : "calcium and magnesium deficiency in orchids".