I'm CymMV Positive

[DebsC]

Nichole, first let me say I'm sorry for every plant you get a positive on. I know the feeling. I'm in the midst of virus testing my collection, too.

Are you dumping every positive plant? Or are you thinking of keeping some in a secluded area?

[MuscleGirl'sHobby]

That's interesting info Jerry. Thanks for sharing it. I am worried that I could be getting false negatives if plants were recently infected, so plan to be extra vigilant even with the ones who seem to be in the clear as of now. Any plants that begin to show symptoms down the road will probably be re-tested.

Debs, as of right now I've not tossed my positive plants. They are secluded though. I think I'm going to keep a small indoor growing area for them until they go to orchid heaven. Those who have tested negative and have no funky symptoms will go in the greenhouse where they will have more elbow room.

[DebsC]

Since I grow mostly the older 'classic' cattleya's, I expected to find a few positive and I have.

I don't intend to toss out plants that can't be replaced, either. Just wondered what precautions you were going to take, Nichole?

From everything I've read, some virus isn't passed on though insect vectors so I plan on putting 'clean' plants on opposite sides of the greenhouse from the positive plants.

Any input from anyone?

[lambelkip]

Originally Posted by DebsC

Since I grow mostly the older 'classic' cattleya's, I expected to find a few positive and I have.

I don't intend to toss out plants that can't be replaced, either. Just wondered what precautions you were going to take, Nichole?

From everything I've read, some virus isn't passed on though insect vectors so I plan on putting 'clean' plants on opposite sides of the greenhouse from the positive plants.

Any input from anyone?

Debs, as I said in an earlier post, viruses can and do get passed on by insects. it's somewhat rare, but that's pretty much the only way they're spread in nature. You're playing with fire by keeping your infected plants. If you're not willing to destroy the infected plants, you should at least spray for insects regularly, even when you don't see signs of an infestation.
test your clean plants again in a few months, and if you see signs of the infection spreading, please reconsider your decision.
I should also not that it may be illegal to knowingly keep infected plants, unless you have a plant pathogen and quarantine permit.

[Jerry Delaney]

Any plants that begin to show symptoms down the road will probably be re-tested.

Sounds like a good idea Nichole. I have about twice or three times the orchids I should have in the space available and so am probably contributing to the problem instead of aiding the solution!

Since I grow mostly the older 'classic' cattleya's, I expected to find a few positive and I have.

I think you bring up a very important point Debs. I also keep a number of the old "classics" and if we know the truth, depending upon how we got them, the plants may have been infected before we even received them. I don't know about you, but a number of my plants were derived as 'gifts' from friends, many who have passed on. I once heard an old timer state that if the orchid was registered before you were born, odds are it's virused. I suppose it depends upon ones age. An additional point is that in the early days of mericlones much larger amounts of tissue were used and if the plant was virused, the odds increased that virtually ALL of the mericlones were virused. Many of these were very popular plants and in the early market of mericlones and hobbyists snapped them up quickly since the only alternative was to get a division of the original. I just recently discarded a L. purpurata that I now know is virused. Problem is, it was a gift from a friend and I don't know if it contracted the virus while in my collection or if it was already infected when I got it. I think that perhaps we should put the question of viruses in the same category as insect problems. I often say there are only two kind of orchid growers concerning insects; those who have them, and those that are going to get them!

[Gin]

Maybe one way to get an idea of how things are spread is to buy a young seedling test it, if clean put it with the known infected plants then re test it down the road . Just a thought .. Gin

[camille1585]

Originally Posted by lambelkip

Debs, as I said in an earlier post, viruses can and do get passed on by insects. it's somewhat rare, but that's pretty much the only way they're spread in nature.

Actually, CMV and ORSV are both viruses for which no insect vectors are known and which don't spread via pollen/seed either. That's what I dug up in journal databases, including somewhat recent publications. Research has shown that there is a very very low incidence of the viruses in the wild, while cultivated orchids sometimes attain up to 70% infected plants at some growers. They are very likely only transmitted mechanically during division, repotting or transfering sap of infected plants to healthy ones while touching them.

I have an infected Cym, but since it lives completely apart from most of the other orchids (another country) I'm still keeping it.

[camille1585]

Originally Posted by Florida_guy_26

Ok, health 101- here is how things work in animal cells, A virus infects a healthy animal cell, that cell releases chemicals called interferon as it is attacked and succumbs to infection. The viral cell usually injects RNA into the nucleus of the animal cell and the RNA tells the DNA in the cell to make new virus cells. As the Interferon reacts with other animal cells it bonds and forms a protective coat on the other animal cells so they become resistant. There are also antibodies which disable the movement of viruses and bacteria and then white blood cells to eat the immobilized bacteria or virus. There are no known protective or immune cells in plants which would explain them getting viruses. I hope this helps for anyone who wants to know how the process works.

I don't know a whole lot about mammals, but its actually quite different in plants. There is no interferon pathway. Instead plants defend themselves by RNA silencing which is where a specific sequence is destroyed by the plant proteins. When a virus multiplies it has to become double stranded, and plants recognize dsRNA as foreign. If the plant manages to recognize the virus, it can kill it, if not the plant becomes infected. There is increasing evidence that RNA silencing also has a defense role in mammalian and insect cells. Knockdown of the system shows increased virulence of some mammalian viruses.

[MuscleGirl'sHobby]

Very interesting Camille. So the journals are saying that CymMV and ORSV can't be transmitted by insect, but only by human means. This is particularly unsettling to me since I've got plants that have never been in contact with one another who have tested positive. While I can attribute overcrowding for the infections of a couple of my plants, there are some who've been totally on their own, but in the same room on a neighboring shelf. This is why I assumed that it had to be insects transmitting the virus between my plants.

If insect are not responsible, this means far more plants came to me infected than I'd like to think. One plant that tested positive has been in my collection since late January and has not been within rubbing or dripping distance of any infected plants. So, unless a 10 minute soak in full strength bleach wasn't enough to fully disinfect my tools, this 'chid was infected by other means.

[DebsC]

Originally Posted by MuscleGirl'sHobby

Very interesting Camille. So the journals are saying that CymMV and ORSV can't be transmitted by insect, but only by human means. This is particularly unsettling to me since I've got plants that have never been in contact with one another who have tested positive. While I can attribute overcrowding for the infections of a couple of my plants, there are some who've been totally on their own, but in the same room on a neighboring shelf. This is why I assumed that it had to be insects transmitting the virus between my plants.

If insect are not responsible, this means far more plants came to me infected than I'd like to think. One plant that tested positive has been in my collection since late January and has not been within rubbing or dripping distance of any infected plants. So, unless a 10 minute soak in full strength bleach wasn't enough to fully disinfect my tools, this 'chid was infected by other means.

I have read and read and READ everything I can get my hands on about CymMV and ORSV in orchids.

The one fact(?) I've found in all the articles I've read so far is there is no known transmission of virus through insect vector.

Dirty tools, pots potting media and hands are the main cause of spread as well as sap dripping from an infected plant to or on it neighbor. Water from an infected plant draining into another pot is also suspect.

From the results of testing in various orchid growing and exporting countries, seems more likely than not to purchase an infected plant.

http://www.fshs.org/Proceedings/Pass...0(SIGMANN).pdf

The viruses are very common in commercial nurseries world wide. Some have rates as high as 70-90%

All this is truly discouraging and I can't see that much is being done about it, from what I've read.

Until commercial growers screen their stock for virus and offer only virus free plants, I have the feeling we're fighting a losing battle.