Opinions on viruses

[katsucats]

I think the expense of testing every single orchid is not an excuse for not testing at all. No one expects that someone who has thousands of orchids test them all. Not even Six Sigma would prescribe this. Quality control is a balancing act of confidence and cost, after all. If you test a randomly selected subset, then you could calculate a sample mean and variance, and estimate the population at some confidence. You could look up the binomial approximation to Gaussian test to find out how many you need to test. For example, if you find that 10% of your plants are virused (which isn't unreasonable, in my experience), then you only need to test 139 to be 95% confident that your collection is between 5%-15% virused. If you test 50 plants and you find less than 3% virused, then you could say, again with 95% confidence, that virus isn't really a problem in your collection. This is what pollsters do -- they don't ask every single person in the country to see who they would vote for.

Once you know the rate you could decide whether to take further action. Some people might find a certain number acceptable. But if I buy three plants from a seller and get one virused, or I buy two and both are, I highly doubt that's a coincidence. For example, the chance that out of thousands of plants, I happen to get the only two that are virused is essentially nil. I assume that these vendors have a huge virus problem, and it isn't all that uncommon in the industry. Unlike MJG, I remember buying several orchids off eBay as early as 10 years ago, and found a third of them to have viruses. I highly doubt the businesses that people have come to respect, like SVO, Andy's, H&R, et. al. never test a plant, and I would gladly pay $35 for one of Andy's admittedly tiny Dendrobiums than an oversized plant off eBay for $15 with a high virus rate (some of the plants I bought off eBay were a great value in terms of size until you realize that they are 33%-100% virused).

[SouthPark]

Originally Posted by katsucats

I think the expense of testing every single orchid is not an excuse for not testing at all.

Can definitely see your side of things there! Although, maybe just depends on circumstances, conditions, and a grower's own choice and/or view ------ as well as on the grower ----- eg. new grower, commercial grower, etc.

I think that - if possible - whether particular favourite orchids have a virus or not ------- one could maybe assume no virus, and then aim to make back-ups (divisions) ------ to spread the eggs out in different baskets.

[katsucats]

Originally Posted by SouthPark

Can definitely see your side of things there! Although, maybe just depends on circumstances, conditions, and a grower's own choice and/or view ------ as well as on the grower ----- eg. new grower, commercial grower, etc.

Of course growers have a choice, a choice that I might disagree with, but I'm not them. Personally, I see viruses as a man-made (i.e. man is the primary vector) problem that has the possibility to back-spread into nature and destroy native populations (this according to a scientific researcher). I also see it as a preventable problem that became very expensive due to negligence over a long time. That no man is an island, and while they might not care that they have viruses, there is always the possibility that those viruses escape (e.g. with visitors touching plants, orchid shows, insects if outside etc.). I personally believe I should leave a hobby better than before I came in.

Now, I am no moral authority, nor are my standards necessarily the objective standards by which everything is judged. But in my garden, whether a plant remains healthy is immaterial; if it has a virus, it goes in the trash, period. And if one day, I have a cultivar that wins 14 FCC/AOS awards, and the source plant gets virused, then I will destroy that so as not to let its inferior genetics pollute the gene pool. Because as long as there are healthy plants with genetic variation, the genes exist to recreate any phenotypic expression with enough trials.

But I guess this philosophy is sort of unwarranted since I was just trying to give Nlamr some basic reasons on why he might want to test, and how he could test without testing every single plant.

Originally Posted by MJG

In terms of statistical testing, a simple random test in this example would not be sufficient. You'd need a stratified design plan (ie identifying and testing differing segments of the overall population, not just random samples from the whole). Each stratum once identified would have its own calculated sample size, blah blah blah. It gets complicated. A random test of the entire population without using strata becomes a broad brush when you have pockets of orchids raised and grown differently. You can end up with an overall false sense of confidence or otherwise skewed results with a simple random test.

I was making the assumption that every orchid has equal probability, and that there are no interaction effects (but to that end, we could randomly choose orchids from different grexes and test a grex further if an orchid test positive). You're right, of course, that it's not that simple, and that we would hire statisticians to be as rigorous as possible. I guess even if it is not rigorous (and highly flawed), the general process still makes sense since testing some plants give a high level picture over testing no plants. I guess instead of calling it statistical testing, I would prescribe testing some plants periodically over testing all plants at once.

[SouthPark]

Originally Posted by katsucats

Of course growers have a choice, a choice that I might disagree with, but I'm not them.

Definitely ok! Just as there are so many varieties of orchids in the world, there are so many different people, with different views.

My view of the universe or the world is ..... it doesn't last forever. As I see it, most things don't last forever - including this solar system and this galaxy.

We also know about - even if a virus does strike orchids ------ there will be those orchids that don't get affected by that particular kind of virus. So some 'evolution' or (cliche term now) ----- 'selection' can/will occur. Orchids will survive - as long as our planet is still hospitable for them (and us).

The other thing is - us humans are currently doing a 'great' job in doing nasty stuff to the body (the earth) - just like bacteria/parasite/virus does to whatever they get onto. Human activity do enough bad stuff already --- to the earth ----- to everything - including plants, animals etc. It's not 'unnatural' though. We're part of 'nature' too. The matrix movie does have a point ----- humans are like a virus/parasite. Very true. But at least many of us are good at heart.

Regular virus aren't 'bad' or 'nasty' as such ...... they don't have brains. They just do what they naturally were programmed/evolved to do.

My view is - if it's important for a grower to test for virus, and/or ensure their collection has no virus (or unlikely to), then that's quite ok. And if other growers don't want to test etc ..... also ok.

I definitely see your side too. It is a good topic actually. It's good to see the various views.

A lot of us growers - you, me, everybody here really grow beautiful orchids - and we care for them ----- genuinely. Each grower has their own way of doing things ----- we see that here and everywhere. It's all 'natural' - a part of nature.

[estación seca]

The problem is already solved - ask the vendor in advance whether the plant has been tested for virus. Then the buyer can make a decision.

If I went into the orchid business I would be a lot more careful than I am now. But I'm not in the orchid business. I don't want to pay extra to test plants that show no signs of virus.

[MJG]

I had an experience recently that helped form my expectations and understanding of viruses and grower practices.

I bought some orchids from Hausermann this spring. Two were virused. The response they send me after I emailed them is as follow:


We are sorry to hear about the virus test on our plants. We do test all of our plants before mericloning and practice sanitation habits as best we can.

We will be glad to credit you on these two plants, however we cannot in the future certify completely virus free plants. We propagate many of our own plants but we also bring in plants from many other sources (to create more variety) where we cannot control their virus testing,sanitation etc. It simply is not practical to test all plants from other sources. I would like to point out though that these positive tests are a rare occurrence


I think if you really want to understand what the likelihood is of getting a virused plant from a vendor, it is worth a call to understand their practices. But apparently you also need to understand where they source their orchids, and where the specific orchid you're interested in came from. It's not as simple as "Do you test your orchids?", unfortunately.

In terms of statistical testing, a simple random test in this example would not be sufficient. You'd need a stratified design plan (ie identifying and testing differing segments of the overall population, not just random samples from the whole). Each stratum once identified would have its own calculated sample size, blah blah blah. It gets complicated. A random test of the entire population without using strata becomes a broad brush when you have pockets of orchids raised and grown differently. You can end up with an overall false sense of confidence or otherwise skewed results with a simple random test.

I wouldn't expect your average orchid grower to do this, or to get it right if they did. Large agricultural companies certainly run statistical tests (hiring a statistician to design and develop the test results). But even then a company is not go to do this unless they are dealing with something (eg, crop yield with different fertilizers) that's going to affect their bottom line in a meaningful way.

[SouthPark]

Also one day in the future (just hopeful !) ......... there may be a cure!!!!!! One little - but very painful jab with a needle ----- and no more virus.

[SouthPark]

True! And is it true that some test kits can provide 'false positive' results? And sometimes, growers can't be sure if say a bug or something that had hung around on a nearby neighbour's orchid, then comes visit our place, and proceeds to infect another orchid. Outdoor growing that is.

For large nurseries with thousands or hundreds of thousands or million orchids etc ........ totally agree ------ practically impossible to test them all, and guarantee them all. And even after having successfully tested the whole lot of them (and then 'assuming' all are virus free) ...... there's always going to be uncertainty as to whether any 1 or more becomes infected at some time later.

So for the super wary home grower -- a combination of testing, plus good safe 'gardening' practices, plus making backups/divisions ...... should cut down on a lot of issues.

[Roberta]

SP, if you make a division of a virused plant, both pieces will be virused. It's systemic, not local. If you have a vector that might be infecting some plants and not others (the primary vector has two legs, a clippers, and sometimes takes shortcuts "just this once...") maybe it would help to have a "spare". But in general, two virused plants is no better than one, and probably worse because of space considerations. Also pretty hard to divide a plant without handling it... making many more places to spread the juices.

[JScott]

I spoke on this topic at some length in a different thread not too long ago, so I won't be as detailed here, but to sum up my feelings on viruses: I don't test for viruses. Most virused plants show no sign of infection, as long as they are grown well (as Ray said). I am careful with hygiene to avoid spreading viruses, because a virus that is asymptomatic in one plant may cause disease in another plant, but other than that, I don't worry about it. I probably have plants carrying viruses, but none of those plants are sick, so I couldn't tell you which ones do or do not have viruses. I've heard of people testing every new plant they buy for viruses and destroying any virused plant even if the plant is in good health. I think that is excessive and extreme.

I also agree with ES and Ray in that there is and should be a higher standard for those who grow and distribute orchids professionally. I know which nursery Ray is talking about, and I am very put off by the fact that they continued to sell plants they knew to be virused without informing their customers.

I recently bought several different plants of Cattleya tenebrosa of various high quality parentages, and the grower informed me that the plants had been tested and were virus free. I think that is going beyond the call of duty, and I appreciate it, but I would have bought them anyway even if they hadn't been tested.

I don't think it's worth worrying about beyond taking reasonable precautions regarding hygiene, but we should be doing that anyway, because proper hygiene does more for plants that just protect against the spread of viruses.