Hosta Virus Myths
contributed by C. H. Falstad
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.
*NEW* 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.
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.
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.
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