Hosta Virus Myths
contributed by C. H. Falstad
MYTH - HVX spreads easily/HVX is difficult to spread.
FACT
- Which is it? Dr.
Lockhart, who is credited with discovering HVX has said it is difficult to
spread, while others say it is easy to spread. It depends on the point of view.
A virologist considers it difficult compared to other viruses which can spread
more easily because they are transmitted by insects or other vectors. Gardeners
and nursery owners on the other hand feel that it spreads easily because it is
easy to spread it while doing the things they normally do with the plants, like
cutting flower scapes, damaged leaves, or dividing. In this case there is no
myth because both are true.
MYTH - Some hostas are immune.
FACT
- The basis for this myth (and it is a
dangerous myth at that) is a study done by Dr. Lockhart. In this study several
varieties were not infected despite numerous tries. The report on this study in The
Hosta Journal did unfortunately use the word "immune" to describe
these plants. Testing for this "immunity" was not exhaustive, and the
use of the word was clearly a case of jumping the gun. Since this study, one of
the "immune" cultivars has tested positive (not the actual plant from
the study), and this should be taken as evidence that these cultivars are not to
be considered truly immune unless further testing proves them so. In a
sidelight, articles mentioning this "immune" list have started adding
plants that were not in the original study. One included 'Gold Standard', which
is one of the most easily and heavily infected in the marketplace. No hostas
should be considered immune at this time.
MYTH - Plants infected with a virus may recover.
FACT
- Viruses do not just
disappear, nor does a plant "fight off" an infection. The virus is
permanent and will be with the plant until it dies. For practical purposes in
the garden and nursery, there are no cures for viruses.
MYTH
- Hostas
from Tissue Culture will not have viruses.
FACT
– If a hosta has a virus before going into tissue culture, the virus will
be propagated along with the plant. Many infected hostas in the marketplace were
tissue-cultured. Plants that were clean after the tissue culture process may
also be infected when being grown on. Labs are beginning to test all propagating
material so in the near future tissue cultured hostas from those labs will be
clean.
MYTH
- All
hosta cultivars will exhibit the same symptoms if infected with the same virus.
FACT
– Symptoms can vary
considerably with the same virus, and different strains of a virus may cause
different symptoms.
MYTH
- All
mottled foliage in hostas is caused by viruses.
FACT
– Mottling patterns in hostas can
have a variety of causes, some of them environmental, and many have causes which
we do not yet understand. 'Xanadu Paisley' has been repeatedly tested and
despite its similarity to HVX symptoms has yet to be shown to be infected with
any diseases. Old plants like 'Cynthia' and 'Filigree' also have no known cause
for their mottled appearance and have never been know to pass this trait to
other plants.
MYTH
- Viruses
will kill, or at least severely inhibit growth of the host plant.
FACT
– Eventually, some
deterioration in the health of the plant can occur, but a plant may survive for
many years when infected with a virus. Different viruses affect the plant's
health at different rates, but some effects may go unnoticed.
MYTH - If symptoms disappear after showing up in a previous year the plant has
either cured itself or didn’t have a virus in the earlier year.
FACT
– The expression of virus symptoms
can disappear, but this does not mean the plant is cured. The virus is still
present in the plant and still able to infect other plants. Sometimes this can
be due to environmental factors that might reduce the rate a virus replicates
thus preventing a high enough population, or titer, to effect expression.
MYTH
- Removing
a leaf showing infection, or dividing out the portion of the hosta showing
symptoms will help cure the plant.
FACT
– Removing some
symptomatic tissue will have no real effect in "curing" a plant of a
virus. The virus is already in all or most all parts of a plant by the time
symptoms show.
MYTH
- All
plants infected with HVX will show symptoms immediately.
FACT
– To the contrary, many
plants in Dr. Lockhart's study did not show symptoms after three years despite
testing positive for infection. We do not know if they will ever show symptoms,
but they are infectious in this state.
MYTH
- If
the symptoms have not spread to nearby plants the virus is safe.
FACT
– If a virus is
"safe", how did that plant catch it? The only way to tell if HVX has
spread to other plants is through ELISA or other more sensitive scientific
testing. It may be years before infected plants show symptoms.
MYTH
- If
a plant doesn’t show symptoms it doesn’t have a virus.
FACT
– It can take years for an
infected plant to show symptoms. During this time it very much can infect other
plants. Only careful scientific testing can determine if a plant that does not
show symptoms is infected with a virus - there is no way for the gardener or
nursery owner to tell.
MYTH
- HVX
is the only virus affecting hostas.
FACT
– There may be more than
ten viruses currently known to be found in hostas. HVX is now the most common by
far, but Impatiens Necrotic Spot, Tobacco Rattle Virus, and Tomato Ringspot
Virus have been frequently identified. Some as yet unidentified viruses have
appeared also.
MYTH
- Symptoms
of Hosta Virus X look attractive.
FACT
– Actually, this is not
really a myth. The effects of HVX on some hostas can be attractive to many, thus
heightening the risk of introducing the virus into the home garden. In addition
to the mottling, these symptoms can include making the infected plant more
compact and more glaucous. Nursery professionals and home gardeners alike have
actually named HVX-infected hostas and offered them as new varieties.
MYTH
- Virused
hostas are worth more money than healthy hostas.
FACT
– Well, does this really make any sense? If you buy a hosta for $5 and
infect it with a disease as common and widespread as HVX, how could it possibly
be worth more? When infected with an incurable disease, it should be thrown away
because it is no longer worth anything. Putting a different name on it once it
is infected doesn't really change this.
MYTH
- If
we pretend the virus doesn’t exist it will go away.
FACT
– If we ignore the
presence of Hosta Virus X in our gardens or nurseries, it will continue to
spread until many more plants have it. In time, the number of infected plants
will increase beyond any hope of eliminating the virus. It is irresponsible to
keep the virus around, because it can infect other plants and spread itself. All
plants exhibiting HVX symptoms must be destroyed immediately to prevent further
infection, and in nurseries all plants in a batch that had symptomatic
individual plants must be also considered infected and likewise destroyed.
MYTH
- Talking
about HVX and other diseases will ruin hosta gardening.
FACT
– While it may be
unpopular in the short term, allowing incurable diseases to run unchecked
through nurseries and gardens will certainly cause worse problems down the road.
The long-term impact of disease-filled gardens on their owners will surely be a
negative one and far outweigh any short-term effects of facing our problems now.
A healthy garden is a source of joy to the gardener, but a garden full of
diseases and other problems will never provide the same enjoyment, and if it
gets worse every year we will lose our enthusiasm.
MYTH
- People
don't want to know about HVX.
FACT
– It is not a pleasant subject, but as adults we all understand
that life isn't perfect. The world contains many harmful organisms, and some of
these do affect hostas. We can face the issues of plant health when we need to.
We understand that sometimes there are outbreaks of a particular disease that
require our special attention. We don't really want to know, but we have to know
to keep our plants healthy. We don't want that information kept from us when the
time comes that we need it.
MYTH
- Viruses are a "grower
problem" and not a cause for concern among gardeners.
FACT
– Hostas infected with HVX
or other viruses ceased to be simply a "grower problem" when the
retailers sold them to gardeners. Thousands of virus-infected plants have
already been sold at the retail level, and many gardens now harbor
virus-infected hostas. All gardeners should be aware of HVX and other viruses
and be careful to avoid spreading them to other plants and to other gardens.