Phalenopsis Leaf Problem

[mSummers]

I bought this Phal Sogo Grape "Fireball" about a month ago and it had mealy bugs so I treated with Orthene. During treatment one of the leaves started developing these spots and I'm not sure what the cause is. Thoughts?

Whatever it is, it is isolated to one leaf and is getting worse very very slowly.

 

[Ozpaph]

look a bit like a burn

 

[mSummers]

It does look like burn, but I don't think that's it. It is in a north facing window that doesn't get direct sun. That's why I think it is something else but I can't figure out what.

 

[mSummers]

Those pictures look awful. Let me see if I can get a better copy uploaded

 

[mSummers]

Here's a better picture:

 

[Bob in Albany N.Y.]

I'm seconding that it's a burn.

 

[gonewild]

Phytotoxicity to the orthene.... chemical burn

 

[Happypaphy7]

does not look like a sunburn at all to me.
It could be chemical burn, although I thought orthene was rather "tender" on the plants.

 

[mSummers]

If it is related to the orthene, it is the first time I've ever had a plant that reacted to it. Since it seems like every plant I've ever bought has had mealy bugs, I've used it on a bunch of them. I'll continue to keep it isolated and see what it does.

 

[cnycharles]

I've heard some people say orthene has killed plants they've used it on, so it wouldn't be unheard of if this was a chemical burn


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[abax]

I've used orthene for years and never seen any damage
whatsoever. Could it be that this leaf touched a cold
window? Maybe just too close to the cold glass? If it's
a fungus, Cleary's 3336 will stop the spread, but this leaf
won't look any better.

 

[Happypaphy7]

I've heard some people say orthene has killed plants they've used it on, so it wouldn't be unheard of if this was a chemical burn


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I highly doubt that they might have mistaken it with some other chemical?
Or maybe certain plants, but orthene in general is considered very mild on the plants.

 

[cnycharles]

These people were using orthene, though maybe they had mixed it with something or certain plants just didn't like it. There are no guarantees that any safe chemical might kill something given certain circumstances


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[gonewild]

If you research Orthene phytotoxicity you'll see that it is phytotoxic to some types of plants. You may use it for years and not have a problem and then suddenly you experience a bad reaction, it happens. That is not to say Orthene is not safe to use, just once in a long while it may cause some leaf "burn". To assume it will never have a phytotoxic effect is wishful thinking.

 

[gonewild]

Here is an example from
"Pest Management Strategic Plan for Potted Orchid Production in Hawai‘i"
(This is a pdf file):

Acephate (Orthene, Precise)
- Efficacy: fair (melon and western flower thrips)
-Advantages: systemic action
-Disadvantages: some phytotoxicity has been observed

The above is about spraying thrips and later in the document they will refer to spraying another pest and see no damage from Orthene. So you can see it happens sometimes and not others.