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Hosta Virus X - A Brief History of the Epidemic by Chris Wilson, June 5, 2005

Hostas have forever been promoted as pest free, care free perennials, but slowly over the past several years the world hosta supply has become increasingly infected with an incurable virus first identified and named in 1996 as Hosta Virus X, or HVX for short. Today, the virus has reached epidemic proportions with virused plants showing up at nearly every nursery and garden center in the world. It is believed that hosta collectors everywhere now have virused hostas in their gardens, and many do not even know it.

The virus showed up in small nurseries in the late 1990's and early 2000's. Many people began collecting these interesting, mottled hostas, thinking that they were new hosta sports. Some infected plants were even named and sold specifically because of their bizarre coloration, such as Hosta 'Leopard Frog', Hosta 'Blue Freckles', Hosta 'Lunacy', Hosta 'Eternal Father', Hosta 'Kiwi Watercoulors', and Hosta 'Breakdance'. These strange looking plants were even purchased and taken from the US to Europe where they were grown and sometimes propagated.

At some point in the past 4 to 5 years the virus escaped from the backyard garden into the wholesale hosta supply in Holland. Virused plant stock might have even been purchased from the US. Because the virus itself takes years to reach a high enough concentration to show symptoms or test positive by ELISA (Enzyme-Linked Immunosorbent Assay, a test to determine the presence of antibodies of the virus), it went virtually unnoticed in the fields. Occasionally growers would find an obviously infected hosta and remove it, thinking that if a plant did not show symptoms it was not infected. In reality, if a single HVX infected hosta was in the field there was a very high probability that every other plant in the area was already infected.

Virused hostas have been regularly harvested and propagated to restock fields. In addition, mechanical weeding machines go up and down the rows during the summer, tilling between the plants often cutting roots and leaves along the way, spreading the virus even more. At harvest time, as plants are prepared for export, power washers are used to spray the soil off the roots. This washing strips off not only the soil but also the outer root material, and the water is continuously recycled to spray off thousands of plants. This combination of mechanical weeding and power washing is believed to have caused a large portion of the field grown hosta supply to become infected in Holland. Although tests of wash water by ELISA have given a negative result for HVX it is speculated that the concentration of HVX in the wash water is simply too low to give a positive test result. Some growers in Holland have now discontinued use of mechanical weeders but exporters continue to use power washing. Growers who have begun virus testing their plants also continue selling asymptomatic plants with a negative test result under the false assumption that a negative ELISA test means "virus free".

In time, the plants being grown in Holland have been sold back to wholesale growers in the United States and other countries around the world, where the cycle continues again in new fields. Obvious HVX infected plants are removed, the fields are certified "clean" by visual inspection and plants are propagated and sold to retail nurseries. It is believed that there isn't a hosta grower left in the world who has not been affected in some way by the virus, and many to this day do not even know it exists. Damage is blamed on frost, herbicide, sun, or drought, but by the time they learn about the virus they have already sold plants and people now have it in their gardens.

The only way to eliminate the virus is to destroy the plants. Wholesale growers and the hosta industry in Holland stand to lose hundreds of thousands of plants and may even lose their livelihood because of the HVX epidemic. The only way to prevent the spread of the virus is to destroy each and every virused plant that shows symptoms, clean and sterilize every tool and piece of equipment that comes into contact with any hosta plant, educate as many people as possible, and we absolutely must stop the propagation and sale of every single hosta infected with Hosta Virus X.

For more information, pictures, or to ask questions about HVX visit the Hallson Gardens Hosta Virus X forum at http://www.perennialnursery.com/forums/viewforum.php?f=63