Cattleya sheaths, dry why? Yellow dead looking -

[quiltergal]

Thanks for the very informative post Andy (you should post more often ). I have a relatively new catt (in my possession since end of Aug) and it's putting out a new growth. I noticed 2 things about it that concerned me a little. It emerged a dark purple color, but it's beginning to green up in spots, and it has a couple of large honeydews on it. It sounds like the honeydews are a good thing, but I'm still not certain about the color. Maybe I just worry too much.

[Tindomul]

Take home message. Patience. Thank you Andy. Your post sooths my worries.

[nenella]

thanks alot Andy ! i enjoyed it too !!!!

[caseydoll]

I have no personal experience with honeydew but this quote is from the book Orchids for Dummies. Maybe there is more than one cause for it?

"If you see clear sticky droplets anywhere on your plant, look out for aphids. This material, euphemistically called honeydew, is actually aphid waste. This sticky substance can also be excreted by any other piecing/sucking insect, such as scale."

As I was typing this I just thought of one of my poor little orchids that I just discovered had scale. It also has a sticky substance on some of the leaves. I didn't put it together until just now that it was honeydew. Weird.

[Tindomul]

Originally Posted by caseydoll

"honeydew, is actually aphid waste. This sticky substance can also be excreted by any other piecing/sucking insect, such as scale."

In that case, I will not be tasting this honeydew until further inspection.
But as for mine, there is alot of honeydew and no damage to the plant, as well as no obvious signs of pests. Hopefully.

[LILROCORCHIDS]

The sticky from the insects are totally different from the sap excreted at tip of new growth or on sheaths ,in my opinion . The Ants search out the sap and even bring the Aphids to the new growth to suck the tender spots. The droplets are formed by the plant . There is sticky that you will find on plants that are infested but not the same as the plants droplets .
Rocco

[Becca]

Originally Posted by Tindomul1of9

In that case, I will not be tasting this honeydew until further inspection.
But as for mine, there is alot of honeydew and no damage to the plant, as well as no obvious signs of pests. Hopefully.

I too have lots of honeydew droplets on one of my catt's...I always called it sap. I have also found it on my cymbidiums.....and I was told that there had to be something like aphids causing this....but I could never find anything, nor have I.....and it still continues. The sap on my cattleya is mainly on the new growth....I have looked and looked....and I can not find any pests other then those dang fruit fly looking things that hide in the soil. It seems happy and is growing very fast with just a hint of purple to the leaf, but no actually burning so the lighting must be ok. I have noticed on some of my other catt's that they start out purplish, and sometimes black-purple and then green up as they mature and all seems well...so until one dies, I am not going to worry to much about it! Hope this helps....reading all the replies in this thread has help allot! Thanks!

[quiltergal]

I've inspected the plant in question thoroughly and it has no pests anywhere on it. I've noticed honeydew before on other plants mostly on new leaves or buds. I thought I remembered reading somewhere honeydew was related to lots pressure in the cells that caused them to ooze. But don't quote me on that. I may have been hallucinating!

[Tindomul]

Originally Posted by quiltergal

I thought I remembered reading somewhere honeydew was related to lots pressure in the cells that caused them to ooze. But don't quote me on that. I may have been hallucinating!

Well I must have been hallucinating right along with you cause I also remember reading that.

[Rosim_in_BR]

Let me give my cent of contribution. I don’t think that internal cell pressure has something to do with the droplets seen on buds, sheaths, leaves, or sepals/petals tips. The plant has other mechanisms to deal with cell pressure, like loosing water under the form of vapor, not droplets. Professors Koopowitz, Joseph Arditti and David C. Jeffrey (University of California)* analyzed orchid exudates to understand the implications on pollination and myrmecology. They technically confirmed what was long known, the droplets are rich in sugars, several types of sugars. As we know, sugars are the basic source of energy for the plants. Why would some orchids put out its precious source of energy, hardly made up through photosynthesis and other chemical processes?
The researchers concluded and I quote them: “there appears to be no correlation between the sugar content of exudates and orchid pollinators”.
Although those sugar droplets can be found on flower parts, they do not seem to attract any pollinator. Also, the plant produces them on the leaves, far from where it would be useful (near the column). Or, when there is no flower on the plant! Their suggestion is that the plant exudates sugars through those droplets as attractants for ants, which feed on them, not pollinators. What the plant gain doing this? Their suggestion: protection! The presence of ants on the plant would help repel grazers. In other words, the droplets would function as a mechanism the healthy plants use looking for protection.
So, Rocco is on the right path when he says that sticky from insects is totally different and also that orchid exudates attract ants.
All this leads to the conclusion that those droplets produced by our plants when in normal cultivation conditions are not symptoms of any disease or malfunction, on the contrary.
My own experience growing orchids for 25 years leads me to the same conclusion.
Sorry for the long post and the paste English. If something is not clear, let me know and I’ll try to rewrite.

* David C. Jeffrey, Joseph Arditti, Harold Koopowitz (1970)
Sugar Content in Floral and Extrafloral Exudates of Orchids: Pollination, Myrmecology and Chemotaxonomy Implication
New Phytologist 69 (1), 187–195.
doi:10.1111/j.1469-8137.1970.tb04062.x