The Most Common Orchid Viruses: CymMV & ORSV [Orchid Health Blueprint]

In our first installment, we introduced viral pathogens and their devious ability to make their way into your orchid collection unnoticed. We'll now focus on the two most common viruses that infect orchids.

Many viruses are spread by insect vectors like thrips, aphids and mites. We’ll talk about these later. However, the two most common viral pathogens found in orchids, Cymbidium mosaic virus (CymMV) and Odontoglossum ringspot virus (ORSV), are not transmitted or spread by insects. Instead, you play the role of the vector with all your tender, loving care. Viruses can be spread by primping and preening with dirty tools (known as mechanical transmission), reusing dirty pots and potting media and not cleaning hands or work surfaces. Virus particles live in plant cells and are released when the leaf is cut into or wounded during any kind of orchid maintenance or division. Both CymMV and ORSV are very stable pathogens that can live outside of your orchid for very long periods of time. Let’s take a closer look at both of these pathogens:

Cymbidium mosaic virus (CymMV)

Cymbidium mosaic virus (CymMV) is a Potexvirus and probably the most common and widely distributed of the orchid viruses. It is generally found only in cultivated orchids, not those found in the wild. Mechanical transmission via tools and such is the way it is spread, not by seed or insects. Symptoms typically typically include chlorosis or necrosis on the foliage usually as a mosaic pattern, lesions or streaks (Figure 2). Sunken necrotic spots may also occur on the leaves (Figure 3). Flower symptoms consist of flower break (irregular discolored spots or streaks on the petals) or as necrotic streaks or sunken spots on the petals. Flower symptoms generally do not appear until after the bud has opened for a week or more. Freshly opened flowers rarely have symptoms.

Less obvious symptoms can also occur such as slowed or stunted growth, poor flowering, or overall poor plant quality. For orchids recently infected with CymMV, it is common for the plant not to exhibit any symptoms until the first time the plant flowers or becomes stressed after infection. Some orchids never display symptoms. Even without symptoms, the virus is present, infectious and poses a risk of infecting the rest of your collection.

Odontoglossum ringspot virus (ORSV)

Odontoglossum ringspot virus (ORSV) is a Tobamovirus and was once referred to as Tobacco mosaic virus orchid strain (TMV-O). It was determined that these two pathogens are very closely related but distinct enough to be considered separate viral pathogens.

Tobamoviruses other than ORSV are not considered to be serious pathogens of orchids. As with CymMV, ORSV is also spread through mechanical transmission only. Foliar symptoms generally include chlorotic or necrotic rings, spots, or streaks which may or may not be sunken (Figure 4). In the case of orchid varieties with reddish or violet pigmented leaves, the symptoms could include intense red pigmentation. Flower symptoms are common with ORSV, usually as color break (Figure 5). As with other viruses, ORSV-infected orchids might not exhibit any symptoms while still serving as an infectious host.

These two viruses often occur individually as a single infection. However, if an orchid is exposed to both viruses, they readily occur as a dual infection (Figure 1). A CymMV & ORSV dual infection may cause an enhancement of the symptoms that would have been otherwise expected from a single infection.

Stay tuned for the next Orchid Health Blueprint installment: a primer on other viruses that can infect orchids.

Contact us

We’d love to talk with you about how we help you grow a healthy and profitable orchid collection by empowering you to detect and remove plants impacted by pathogens before they spread and cause irreversible damage.