Should I be testing all new orchids for viruses?

[LauraM]

From reading many threads here, I suspect this is a question that comes down to opinion in the end. I have not tested any orchids to date for anything, nor do I suspect any of being virused (if infected, they are asymptomatic so far). But I'm wondering if it's really worth the cost to test all of the orchids I have currently (around 30, I think, between my mom and I - I care for hers when they are out of bloom), and then test all orchids acquired from here on out? I'd probably be doing the Regabio CymMV + ORSV combo test strips.

Also, when I'm at school, most of my orchids live around tons of other plants. Any idea the chances of transmission from other types of plants to my orchids? I don't know my plant viruses/plant virus transmission near as well as my human viruses.

For what it's worth, I'm extremely careful about preventing transmission when it comes to repotting, etc. - I had various central lines for several years so when I say I sterilize everything I mean I really sterilize EVERYTHING lol. I also ended up with about 200 new (sterile) blades for the 2 scalpels I have for non-orchid reasons (long story haha) so I've been using new blades each time, though that feels wasteful so I may start reusing. All of my orchids do live pretty close together for the most part though, and while I try not to let the leaves touch unless in transport and haven't had bug issues I'm just not convinced they couldn't manage to infect each other. Maybe I'm just over paranoid? Done too much reading on this perhaps?

[Roberta]

Personally, I test on suspicion (color break in flowers, or failure to thrive for a plant that doesn't seem to have other reason to not be thriving) Other orchid collectors are meticulous about testing everything. I think it comes down to the question... if you have an otherwise healthy plant that you find has a virus issue, how will you use the information? Throw out a plant that otherwise is performing well for you? Keep it but keep it away from the rest of the collection? Note that plant viruses don't spread easily (plants don't sneeze and cough), the main mechanism is the exchange of juices. So if, when you make a cut on a plant or otherwise put it in a situation where it could transmit fluids to another, you maintain good hygiene practices, you greatly reduce to likelihood of spreading disease (Those good practices also reduce the chances of spreading other, more common, pathogens like fungi or bacterial issues) I think it unlikely that virus would spread by simply having leaves touching. Having them drip water on plants below could be more problematical since water that goes through a pot can pick up pathogens. Again, not only viruses but also fungal/bacterial problems. So... you need to evaluate your own tolerance for uncertainty, as well as the expense and your attachment to the "individuals" in your collection. I think there is not one right answer... you need to weigh the pros and cons and decide for yourself.

[Ispahan48]

Excellent questions. Since you are a hobby grower like myself, I would absolutely continue to use disposable razor blades, one for each plant you need to cut and/or groom. When repotting plants, I wear disposable gloves and lay down newspaper to cover the work surface, all of which are disposed of and changed in between plants. I am also careful to never let my plants share water. Since I only have about 30 orchids, that means every one has its own cache pot to facilitate this.

Some might think it overkill, but I did invest in testing all of my current collection and disposed of any that were virused (it ended up being about 25%). I use either the Agdia or RegaBio strips to test every new plant as it enters my collection. I have a zero tolerance policy for CymMV or ORSV. Even as a hobby grower, I noticed a significant difference in overall vigor, resilience and floriferousness once the asymptomatic sick ones were rogued out.

One argument I often hear that makes no sense to me is that one should not bother to test for CymMV or ORSV using the strips because more than 20 other viruses are known to infect orchids. To me, that is like saying one should not test for HIV or Hepatitis in humans because humans can be infected with hundreds of other viruses. CymMV and ORSV are known to have detrimental effects in orchids overall, whether or not certain individual plants or strains can remain asymptomatic after infection. And they are relatively easy to test for.

As far as I understand, these two viruses are mostly spread through mechanical means and unsanitary hygiene practices among growers.

If I had hundreds or thousands of orchids, I would probably have to modify my approach somewhat and only test highly suspicious plants or more likely to be infected groups of plants. Which brings me to my final piece of advice: be mindful of your source and the type of orchids you are obtaining. In general divisions and mericlones will have much higher rates of virus than young, seed-raised plants. The older the cultivar, clone or individual plant, the more opportunities it has had along the way to become virused before it reaches your hands.

[SouthPark]

I've never carried out any virus test on my orchids before.

I've never encountered those issues such as colour breaks and alien ring circles and patterns etc. This doesn't mean all my orchids are virus-free.

I basically don't worry about it - and I just follow some procedures that hopefully cut down chances of spreading and propagating of diseases (if any) among the orchids.

Each grower will have their own views about virus testing.

If it's important to a grower to test for viruses and to have a long-term plan/strategy for virus testing, then that's ok.

The natural environment can give viruses themselves a hard time ------ ie. viruses probably find it hard to survive themselves. We just got to make things hard for them ourselves, and try to do things that prevent them from spreading around (for cases where we choose to not do virus testing that is).

The universe can be harsh on everything ----- can be. Viruses are just survive basically ----- just like we're surviving. In this case, we just so-happen to be siding with the orchids through choice heheh.

[Roberta]

A consideration - if one is growing in a small space in the house, or in a greenhouse, there can be more reason to be extra-cautious. I grow most of my orchids outside, so even where things are crowded, it's much less so than in a confined space and air circulation is, of course, much better. So the odds of cross-contamination from contact - splashing water, insects, etc. - is much reduced. I keep a propane torch handy, sterilize clippers between plants always. (Razor blades are fine for small plants, but you risk slicing a finger if you try to use one on a thick, tough rhizome... no organic matter is going to survive that torch flame. It's rough on the blades, so they need replacing every 6 months or so, for $10 I can be a sport for the sake of my orchids)

In short, if you are growing in confined spaces, your perspective will be different than that of those of us who can grow in the back yard.

[LauraM]

Thank you all for the advice! I hadn't thought much about what I would do if I did have one test positive, but that's a super helpful way to think about it.

[katsucats]

I'm one of those who tests every single plant, at the earliest convenience when they come into the house. Although I have spent a pretty penny on just the tests, I find it justifiable, and over some experience, I find cheaper ways of testing.

For example, I now do batch testing, where if a vendor has low reviews or bad reputation, or the plants are mericlones or large plants, I test 2 plants with one stick. If the plants look relatively safe, I test 3-5 with one stick. If it's negative, then it means all of them are negative. If it's positive, then I would need to take new samples and retest them using more sticks. That's why low risk samples justify more samples per test. With batch testing, and buying 25 tests in bulk, I find that the cost of the test per plant per one time could be $2-3.

If a plant tests positive, I have the opportunity to ask for a refund for that plant, whereas if they test positive a year later, that's unlikely to occur. I have a big spreadsheet of every sick plant I get and where they come from, so I know which vendors I could trust more. Otherwise I might as well keep buying virused plants that look okay from ethically questionable vendors and never know any better. I see other people on this forum and others online that buy from them, but they are unlikely to listen to my crusade, but I could at least save myself.

Furthermore, I do periodic statistical testing, where I pick random plants to test once in a while, using 5 samples per test. If my culture is right and my growing area has been clean, then this should always be negative. But I can't know unless I try it.

In my experience, the plants that have tested positive never have any really noticeable symptoms, so if I only test when symptoms show, then in my opinion 90% of the virused plants in my collection would escape notice, where they would carry on as Typhoid Marys silently infecting other plants at opportune times. And just because they don't have obvious rings and blemishes now doesn't mean they won't slowly decline in the long term.

I find that I'm a lot more relaxed and less paranoid when I know my collection is virus free. Although best practices are still warranted, and bacterial and fungal problems still exist here and there, I don't have to freak out when water splashes by accident, or if a plant starts declining, I could instantly rule out the culprit hardest to detect.

Furthermore, while viruses have low incidence in nature, it's because orchids propagate by seed in nature. Most viruses are propagated mechanically and cloning plants. Then, when poachers collect plants in nature, or when people grow their plants outside and the disease is spread by insect vectors, or virused green matter is improperly discarded and ends up in the ground, these viruses disseminate back into the native population. Most orchid growers enjoy being in a sort of bubble, no offense to anyone, but there have been scientific studies showing how widespread this problem is, to the point that the researchers worry about viruses infecting and causing extinction in the native populations.

So while not everyone agrees with my judgment on this issue, I test every plant for several reasons:

• It's cheaper in the long run because plants themselves are expensive, and there are hidden costs (e.g. shipping and handling, tools, water, electricity, fertilizer, fungicide, pots, time spent in care, etc.). Let's say you buy 3 plants from a vendor to lessen the blow on shipping costs. If shipping was $15, now your 3 plants might as well be $5 more expensive each. But if one of your plants die from a virus, then the rest of the 2 plants might as well split the shipping at $7.50 each, so the cost basis on shipping alone makes up the cost of testing.
• It makes it much easier to take care of a growing collection. Plant ailments come from cultural problems and infections. Most of the time, bacterial and fungal problems are localized, or at least visible. Virus problems are not. Expensive fungicides like Banrot could kill even stem rot pathogens, but nothing kills viruses that wouldn't also kill the plant. So if you have a problem, it would be easier to figure out what it is if you could rule out viruses. No matter how clean your practice is, there will be a day you will miss a spot when you torch your tools, or water will accidentally splash further than you expect, or you'll get a spider mite or thrip infestation because summer is hotter than usual.
• I would suggest that there is a moral component, in the same way that we don't buy illegally poached plants, we should do our best to contribute to the limiting viral vectors to ensure the longevity of this hobby.

Originally Posted by LauraM

Any idea the chances of transmission from other types of plants to my orchids? I don't know my plant viruses/plant virus transmission near as well as my human viruses.

It depends. There are many viruses that only infect a single genus, but there are also many viruses that infect a multitude of plants. From time to time, you'd find scientific literature noting cross infection from other plants, and this becomes hard to detect, since most growers only test orchids for ORSV and CymMV. But we should note that ORSV is also known as TMV-O, since it's closely genetically related to the tobacco mosaic virus. The TMV is notorious for being able to infect numerous other plants, and have been found to live in the ground for decades after a crop infection. It has been noted to survive months in a compost pile at 130F. Other viruses that may infect orchids would be the CMV (cucumber mosaic), CaCV (capsicum/green pepper chlorosis), TSWV (tomato spotted wilt), INSV (impatiens necrotic spot), and many others. In my opinion, while 99% of orchid virus incidents come from ORSV and CymMV, if the orchids are grown next to crop plants or other mechanically propagated ornamentals, all bets are off. This doesn't mean that you should just give up and not test. It means you could keep an eye on the other plants. For example, if you have monstera with vein clearing (yellow veins) or mosaic spots, you should get that tested.