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.
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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.
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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.
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