Please help with Den. Pha. problem (white layer on back of leaves)

[BrianC]

I had had this Den. Pha. for a few years. I did not make it flower, but it looked healthy.

I found that there was a white layer on the back of most of its leaves (but not uniform) yesterday. I was wondering if anyone could save it.

Some details:

The white layer was a little sticky, but I could not remove anything using water or my hand. I had spayed some fungiside and now trying to place it under the sun hoping to kill the fungi or whatever.

The same thing happened to this Den for years (I did not treat it) but spread recently. I had not notice the problem until three leaves turned yellow within a few days.

Some possible causes:

I had lost 3 Den Pha since we moved from the south to San Francisco Bay area. I guess my Den. Pha did not happy because the night temperature was low during the summer. I put this Den indoors recently and increased the humidity from 50-60% to 70%-85%. The temperature was between 55-70F.

[orchidlady]

The most common reason for a white/silvery appearance to leaves is mites-spider and others. The critters themselves are often so tiny that they are hard to see. If it's spider mites you will see some webbing around the affected areas. I would treat with a mitacide.

Susan

[zainal abidin]

I got similar problem after applying neem oil the subsequent leaves no longer having same problem if it's due to spider mites. Maybe you need to apply some insecticide focusing on the affected side.Zain

[BrianC]

Thanks a lot for the help.

I will try some insecticide tomorrow.

I did not see any net though. And a nearby vanda was OK so far. I cut one of the leaves and found that the white layer was part of the leaf itself.

The den was isolated now. There were too many tree around us.

[catttan]

Thanks a lot for the help.

I will try some insecticide tomorrow.

I did not see any net though. And a nearby vanda was OK so far. I cut one of the leaves and found that the white layer was part of the leaf itself.

The den was isolated now. There were too many tree around us.

Yes, it's spider mites. Treat with insecticide. Dendrobiums and phalaenopsis are particularly prone to spider mite attack. You will notice that they are found on the underside of the leaves which normally escapes watering. A tip given to me by a commercial grower is to wet the underside of the leaves when watering. Following his advice, I don't have a problem with spider mites any more.

[orchidlady]

Thanks a lot for the help.

I will try some insecticide tomorrow.

I did not see any net though. And a nearby vanda was OK so far. I cut one of the leaves and found that the white layer was part of the leaf itself.

The den was isolated now. There were too many tree around us.

Yes, if it is mites, the white layer will be part of the leaves because what you are seeing are the remains of the leaf cells that have been sucked dry by the mites. Whatever product you use, just make sure it covers mites because mites are not insects-they are related to spiders.

Susan