Is this a correct diagnosis? Brown leaves with white spots

[PeteB]

I have a few plants that were inherited and I've been chucked in the deep end of looking after orchids. I'd like to keep these all alive so any advise is welcome!

Two leaves on this orchid are brown with white spots. I believe this is bacterial and the correct remedy is to cut the leaves off with sterile scissors around 1cm below the infection. Then I seal the wounds with cinnamon, spray 3% hydrogen peroxide on the rest of the plant and use a fan for an hour to dry. Would you say this is correct based on the photos in this post?

I also noticed that one of the leaves has a brown tip that I'm sure has been there for a few months and I assumed this was from insect damage as seen by the holes in the leaf (should I just leave this?) Also, as a prevention I believe bacterial infections can happen easier when the plant is stressed so I don't know if a repot is in order?

Thank you in advance!

Images: Orchid rot? - Album on Imgur

[Orchid Whisperer]

Sunburned leaves, and very dehydrated.

The dehydration may be due to a lack of roots. Pull the plant out of the pot. Healthy roots will be firm. Typically they will be green when the roots are exposed to light, yellow or white down in the growing medium where it is dark. Dead roots are soft, or papery, often dark brown. Pull off or cut off dead roots, but if a root seems firm but the wrong color, leave it on.

Post a photo of the bare root plant after you have removed the pot and medium. It will help advise you what to do next.

[Ray]

It's certainly hard to tell accurately from photo's, but I would lean more toward a fungal infection than sunburn. Diagnosis can be helped by noting the order in which things happened.

For example, in the case of sunburn, patches of normally-healthy leaves become blackened, then turn parchment-like, unlike the photos. If the leaves were dehydrated first, and this just appeared, I might lean more toward sunburn, but still not 100%. Also, why would sun affect lower leaves, and not the more tender, new ones? Again, the order of things happening can help.

In some fungal infections, such discoloration is common, and the fungus clogs up the vascular system, leading to general dehydration, and loss of older leaves first.

Your topical treatments won't touch that. I recommend you get some thiophanate methyl systemic fungicide, sold under names like thiomyl or Cleary's 3336.

[MattWoelfsen]

Following up Orchid Whisperer’s advise....

This is sunburn. Phalaenopsis like bright shade. Is this window south facing? It would be better placed in an east facing window.

As advised, remove the plant from its pot after watering it. This will help you slide the plant out of the pot and help you identify dead versus living roots. Green roots are healthy, brown, shriveled roots are dead. Prune the plant of dead roots. Also remove the flower stems by cutting as close to base of the plant without damaging the plant. Do not remove the sunburned leaves, let the plant do that over time.

Then re-pot in fresh bark. I should’ve advised that before you re-pot, pre-soak the potting media so that it is good and soggy. If you removed a lot of dead roots, I would add a layer of Sphagnum moss on top of the bark media, this will help retain moisture. Place plant in an eastern facing window sill. Do not water again until the bark media is dry. You can test for dryness by inserting a bamboo skewer into the root mass, if it comes out dry, water it.

---------- Post added at 08:01 AM ---------- Previous post was at 07:55 AM ----------

My post came after Ray’s. So if his diagnosis prevails, follow the suggestions for combating fungus.

One of the best resources to combat or remedy any malady is this board, but also Google: Saint Augustine Orchid Society.

[Ray]

Originally Posted by MattWoelfsen

One of the best resources to combat or remedy any malady is this board, but also Google: Saint Augustine Orchid Society.

Hah! That's exactly where I went to compare images before I responded.

[PeteB]

Thank you for the replies, I've attached photos of the roots as requested - to me they look OK but perhaps if I were to take the moss away I might reveal more issues.

Before I took on the plants it was on a windowsill that may have been South facing but this was 4 months ago. I might have remembered incorrectly and the leaves may have already been damaged, but I don't remember it being this bad or with white spots.

It's currently on a windowsill facing north and I'm in England with cloudy weather so I'd imagine it's unlikely have been sunburnt here. Possible, but unlikely.

The leaves with the white spots still seem fleshy but watery and they seem very similar to bacterial infections shown from other peoples images online so I can't help feel that it's more likely this, at least as a secondary ailment caused from sun damage as Ray suggests. Of course I do regard all your expertise higher than my own opinion!

[Orchid Whisperer]

For some reason, when I first looked at the original post, I could only see 2 photos through the link.

I am leaning more in the direction of your original diagnosis, or possibly Ray's. I would absolutely cut the leaves back to healthy green tissue. Sterilize blade between cuts. I would keep the plant on the dry side (possibly careful watering of the roots, absolutely no water on the leaves).

I don't really use cinnamon, but you can try it (leaves only, never on roots).

I would not spray with peroxide. After a dry period, and observation to see if the problem spreads, you can wipe leaves with a paper towel moistened with peroxide.

[estación seca]

Squishy and watery is usually bacterial. Fungicides will not help. Copper may help, but it must be done carefully. Read about Erwinia on the St Augustine Web site.

[PeteB]

Hello all - I thought I'd give an update on everything. I'm pretty sure it was actually a fungal infection as I left the orchid a few days and very little happened, I imagine it would have been a lot worse in that period of time if it were bacterial.

I chopped off around 1cm excess around the infected region using sterilised scissors and used cinnamon on the exposed part of the leaf to seal it. There's still a lot more to fix on this but none of it seems to be that dire so I'm leaving it now to prevent too much stress. It seems quite healthy even after 2 weeks of having it's leaf diced up. I kept the stork with buds on out of curiosity to see if they flower.