Orchids Viruses and How To Protect Your Orchid Collection

As if orchid growers didn’t have enough to worry about, orchids can also have viruses! There are actually many viruses, but two are more commonly identified in orchids than the others: Cymbidium mosaic virus (CMV) and Odontoglossum ringspot virus (ORSV).

Fortunately, humans don't get orchid viruses! It might make an interesting science fiction novel though...

How do orchids get viruses? Orchid viruses also are NOT passed through the air. Direct contact between the plant and the virus is necessary. This is one reason why it is not a good idea to reuse water between your orchids, as this can spread viruses in addition to other pathogens (funguses and bacteria) and pests. Instead, give each plant fresh water+nutrients and collect excess to feed to non-orchid plants or your landscaping plants. Shared tools are another possible source of contamination, which is why it is a good practice to sterilize tools or use single-use tools (such as razor blades). Some sources suggest that viruses can be spread via sucking pests, but this might be a less common method of transmission. 

Viruses can also be passed to new orchids if an infected plant is cloned via tissue culture. Theoretically a virus can also be passed onto seed-grown progeny from infected parents, but this would be much less likely and could probably be prevented with sanitary measures. 

How do you know if an orchid has a virus? The only reliable method is to use a virus test kit. There are two main sources that I know of: Agdia and Regabio. I have the Agdia kits, which I bought over a year ago and the price has increased since then. Regabio is available in 50 kit boxes from Taiwantrade, and could be economical if a small group ordered together and shared the kits. 

Can't you tell just by looking at a plant that it has a virus? In my experience, that has not been the case. I've tested plants that have looked suspicious or have been sickly looking, and they've tested negative, while perfectly healthy looking plants have tested positive. For example, can you tell by looking which of these two plants has a virus?

Agdia batch test for two plants showing a line indicating a positive ORSV test.

Does This Orchid Have a Virus? Banfieldiera Guilded Tower 'Mystic Maze.' Has a healthy new growth, but the previous growth is looking quite ragged with creased leaves and discolored spots.

Or, Does THIS Orchid Have a Virus? Oncidium Sharry Baby, a very vigorous grower, has more than doubled in size since I got it a year before this photo. 

And the winner is: Option 2, Oncidium Sharry Baby tests positive for ORSV. 

Since early 2023 I have been testing all new arrivals in my collection and spot testing older plants using the Agdia tests. I batch test 5-6 plants at a time. While this is not a suggested way to use the Agdia tests, it seems to work in the very limited instances where I've had positive results, and there is no way I could afford to test every single plant in my collection with its own test kit. Though batch testing, I've tested almost 50 orchids, and still have tests left. 

The other sneaky way I stretch out my test kits is to cut them in half. The Agdia test kits consist of a stick and a bag of solution. I cut the stick vertically with a sharp pair of scissors, making two skinny test sticks. Then I also cut the bag in half, with some solution in each half. This is certainly not suggested by the manufacturer, but seems to work.

The only plants that I've had test positive are divisions of older legacy plants. The above pictured Sharry Baby was rather large when I got it, and seems likely to have been a division rather than grown from seed, and no other plants from this vendor have tested positive. The other positive was a huge Cattleya intermedia that tested positive for CMV that came from a well-known vendor who has since retired, and was likely something that had been in his collection a long time. None of the other plants from that vendor tested positive for CMV (paphiopedilums that were clearly grown from seed as part of a breeding program). Despite the reports that high percentages of plants from Taiwanese greenhouses are infected, none of the many, many seedlings I've bought have tested positive for viruses, which suggests that growers are aware of the problem and have taken precautions. 

Why worry about infected orchids? First, infected orchids are likely to decline and become less productive over time. I have a lot invested in my collection and I'd like to grow them into specimen plants over time, and I'd rather not waste my time on plants that will fail to thrive. Second, infected plants can spread that infection to the rest of your collection, and while some orchids may be resistant to the effects of viruses, others may be more susceptible. 

Can you cure an infected orchid? No, there is no known cure for orchid viruses. 

What should you do with an infected orchid? First, if you are testing incoming orchids and one tests positive, contact the vendor. In my experience, reputable vendors will want to make things right and will offer a refund or replacement. 

As for the infected plant itself... one could destroy it, and remove it from circulation. I haven't been able to quite bring myself to this point. In one case, I offered the virused plant, with full disclosure, to members of my local orchid society. Someone gladly took the offered free plant, saying that they had plenty of room to keep it isolated from other plants. In the case of the Sharry Baby in the above picture, I still have the plant. I keep it isolated from my other orchids-- in the winter it lives on its own windowsill with a private light fixture and some succulents for company, and in the summer it hangs out on an isolated part of the porch with a nice view 😄. I have been keeping an eye out for a replacement, but a mature, vigorous, floriferous, deliciously scented Sharry Baby is difficult to part with, and I have developed a method to keep this one plant isolated for now. 

How do you avoid getting virused plants? One good way is to buy from sellers who are known to have clean plants. Vendors that I personally have tested multiple plants and have not gotten any virused plants from are: Brookside, Sunset Valley, Andy's Orchids, Diamond Orchids, Big Leaf, Flask and Flora and Orchid Classics. Orchid Board has several discussions about this issue, and other members have published their personal lists of experiences with vendors and seller virus policies. However, the only sure way is to get your own test kits and test for yourself, and you may have different results.

Should you contact vendors in advance and inquire about their virus policies? Unfortunately, only a few orchid vendors will definitively back their products with solid virus guarantees. I'm not sure whether this is distrust of the consumer, the slim margins of the business, or dispute as to the science and effects of viruses on orchids. In conversations with vendors on this issue, some may be unwilling to offer blanket policies but still want their customers to be satisfied and will replace or refund when reasonable concerns are documented.