Both CymMV and ORSV are very stable pathogens that can ally as a single infection. However, if an orchid is exposed to
live outside of your orchid for very long periods of time. Let’s both viruses, they readily occur as a dual infection. A dual
take a closer look at both of these pathogens:
infection may cause an enhancement of the symptoms that
Cymbidium mosaic virus (CymMV) is a Potexvirus and prob- would have been otherwise expected from a single infection.
ably the most common and widely distributed of the orchid
viruses. It is generally found only in cultivated orchids, not Other common orchid viruses
those found in the wild. Mechanical transmission via tools
CymMV and ORSV only infect orchids, and are the most
and such is the way it is spread, not by seed or insects. Sympdocumented and studied viruses of orchids. However, other
toms typically include chlorosis or necrosis on the foliage usuviruses are known to infect orchids, many of which have a
ally as a mosaic pattern, lesions or streaks (Figure 1). Sunken
wide host range that includes house plants, garden plants, or
necrotic spots may also occur on the leaves (Figure 2). Flower
even field crops. All of these may be transmitted mechanically
symptoms consist of flower break (irregular discolored spots
with contaminated tools or media. Some of these other virusor streaks on the petals) or as necrotic streaks or sunken spots
es are also spread by insects or mite vectors, which if present,
on the petals. Flower symptoms generally do not appear until
must also be eradicated to prevent further spread of the virus.
after the bud has opened for a week or more. Freshly opened
These vectors may transmit viruses in one of two ways: a perflowers rarely have symptoms. Less obvious symptoms can
sistent manner (mites, nematodes or thrips) which transmit
also occur such as slowed or stunted growth, poor flowering,
the virus for weeks after last coming in contact with the virus;
or overall poor plant quality. For orchids recently infected
or non-persistent (aphids) which only transmit the virus for
with CymMV, it is common for the plant not to exhibit any
up to a few hours after exposure to the virus.
symptoms until the first time the plant flowers or becomes
Systemic infections are common in orchids meaning that
stressed after infection. Some orchids never display symponce the virus has infected its host, the virus may be found
toms. Even without symptoms, the virus is present, infectious
throughout the plant. For some virusand poses a risk of infecting the rest of
es, especially the Tospovirus group,
your collection.
the virus may infect its host locally,
Odontoglossum ringspot virus
meaning that the virus is limited to
(ORSV) is a Tobamovirus and was
localized parts of the plant. This usuonce referred to as Tobacco mosaic
ally manifests as lesions or chlorotic
virus orchid strain (TMV-O). It was
spots, and the virus is present only in
determined that these two pathogens
the immediate vicinity of the sympare very closely related but distinct
toms. Both infection types are equally
enough to be considered separate vicontagious. Described below are some
ral pathogens. Tobamoviruses other
of the other viruses for which growers
than ORSV are not considered to be
and hobbyists have been known to test
serious pathogens of orchids. As with
and how they infect orchids.
CymMV, ORSV is also spread through
Orchid fleck virus (OFV) is a Rhabmechanical transmission only. Foliar
dovirus which may also be spread by
symptoms generally include chlorotthe false spider mite (Brevipalpus caliic or necrotic rings, spots, or streaks
fornicus), a pest of orchids. Symptoms
which may or may not be sunken
associated with OFV infection include
(Figure 3). In the case of orchid varichlorotic or necrotic speck or spots on
eties with reddish or violet pigmented
foliage.
leaves, the symptoms could include Figure 2 - Healthy leaf on left / leaf on
Tomato spotted wilt virus (TSWV) is
right is CymMV infected Dendrobium
intense red pigmentation. Flower
a Tospovirus which may also be transsymptoms are common with ORSV, species. Photo: Dr. R. McMillan, Homestead Florida
mitted by thrips, a common greenusually as color break (Figure 4). As
house pest. For systemic