White blotches on my phalaenopsis leaf

[carol57]

I wonder if anyone can help me, I have an otherwise healthy phalaenopsis plant which has two fairly large white blotches on one leaf, they have a black ring around each white blotch. Its almost as though the leaf has bleached.
I am not sure if the leaf has a fungus or virus problem or whether it has been bent against the ceramic tile. The plant sits on my kitchen window sill with five other plants which are unaffected.
Any thoughts people ? I have had a quick look through the site but can not see any plant that looks similar.
The photos are of the front and back of the leaf.
Many thanks
Carol

[katrina]

Looks like sunburn to me. Does the sun hit that part of the leaf at any point during the day?

[Hiester]

I would agree with katrina. Looks like sunburn.

[carol57]

Its possible the sun does come in that window quite strongly, but why would the other plants not be affected? Could it be where I have misted the leaves that the sun has burnt through the water?
Thankyou for the answers so far

[JMNYC]

Yes, sunburn. Another reason I grow my phals hanging.

[WhiteRabbit]

Some plants can take more sun than others ...

And it is possible that water on the leaves has been a contributing factor. This only usually happens when foliage is wet while being hit by the sun combined with high temperatures.

Usually, misting does nothing for the plant, and may cause unintended issues.

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[james mickelso]

Most likely sunburn. But......keep an eye on it. If it continues to grow it is bacterial or fungal in nature (akin to pseudomonas) and can be fatal. Black rot on leaves can be paper color but usually black with a greenish or yellowish border. If the white spot surrounded by the black border keeps enlarging, I would isolate it and treat for pseudomonas.

[katrina]

I wouldn't contribute the misting to the sunburn...the mist would've dried up long before the leaf sustained this level of dry burn damage. It's not a speckled damage nor is it wet looking...it very dry and it looks to be on the curve of the leaf. My guess is this occurred at a lower intensity over a longer period of time. That's what it looks like to me anyway.

As for the water/sunlight thing...I really wish I knew where that started. I keep reading it on the web and it makes no sense. I've heard it for years...even in books and magazine...but it makes absolutely no sense. If it were true then all trees/shrubs/all plant life in nature would show damage. What happens to all the plants when it rains in the middle of the day and then the sun comes out after the rain passes? As it very typical all over the world. The tropics are notorious for afternoon pop-ups and then the sun comes out full bore once it passes. If this water/sunlight theory were true then why aren't all plants in nature burned up?

When the temps get really high like they've been this week (mid 90's+) my high light areas soars in temps because it's in full SW sun and it sits adjacent to a paver patio that radiates heat so I actually hose down the plants to cool the leaves. Never burned an orchid from the water on the leaves. The water evaporates far faster than the sun could possibly do any damage.

I guess if you have a thin leaved young seedling of something that isn't suppose to be in high light and you water it and then have it sitting in full sun...I suppose that could cause damage. Maybe. But, I believe there's more to that than just a little water on the leaves. The majority of plants aren't going to experience any damage from this activity.

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[james mickelso]

Katrina makes a good point. I never understood that old wives tale either. It makes no sense. But in a cold climate, water sitting on a leaf might exact some cellular damage. What interests me about sunlight damage is why it is in one spot? Even a bright spot of sunlight that small hitting the leaf would move quickly enough to not cause this kind of damage. And a band of sunlight hitting the leaf would cause a broader area of damage too. I have the same kind of damage on a couple of my phals which started as fungal growth but stopped enlarging and then eventually turned white like parchment. Surrounded by the same black border. I think the plant may fight off the attack and this may be what is left. Most of these type areas on my phals stay black but there are a few that turn white like parchment. Just wondering aloud.

[carol57]

Thank you all for your help, sun burn it is then, now do I just leave the leaf or do I cut it off ? It is just about to flower again after a break so I want to keep it happy and healthy