Introduction

Hosta Virus X (HVX) was first described in 1996 by Currier and Lockhart at the University of Minnesota.  HVX is now a common virus on hosta, and it is a concern to nurseries, garden centers, and home gardeners.  HVX infects many different hosta cultivars, and in some cases can lead to complete death of leaves.  There is no cure for HVX. 
 

Symptoms

Symptoms vary by cultivar and time of infection.  Some hosta cultivars have natural coloring or striping, so it is important to know what is “normal” for a given cultivar.

The most dramatic and diagnostic symptoms include line patterns (especially along veins), mosaic patterns, blotches, puckering, twisting, or ringspots.  However, certain cultivars may only express small necrotic (brown/dead) spots.  And, some plants may be infected but display no symptoms.  This can occur if the plant was infected recently—it can take a year or more for symptoms to develop.  In addition, certain cultivars simply do not express symptoms well.  These “symptomless carriers” add to the challenge of preventing spread of this disease.

Spread

HVX is mechanically transmitted, meaning it can be spread on hands, pruning tools, and by propagation (divisions, etc).  It is a good practice to sterilize tools between plants when pruning or dividing.  Accidentally hitting hostas with a lawn mower or weed-whacker might also spread the virus.  There is no evidence that HVX is spread by insects.

Management and Testing

There is no cure for HVX.  The best management strategy is to prevent the spread of HVX by avoiding the sale and planting of HVX-infected plants.  It is important to remove and destroy infected plants.

Live plant dealers in Kansas that sell hostas should educate employees about this disease.  Plants that are suspected to have HVX should be removed from sale.  The diagnostic lab at K-State has acquired materials to test for HVX.  Clients may submit samples for testing.  Clients should be aware that this test can only detect HVX, even if other hosta viruses are present.  If there is a positive result, the client should contact the Kansas Department of Agriculture to follow up on the situation (contact regional inspector, or KDA plant pathologist Jon Appel at jappel@kda.state.ks.us).  KDA will contact the original source of the plant material (the wholesaler, for example) and will coordinate with the regulatory agency of the source state if it is outside Kansas.

Homeowners should also be aware of HVX and avoid purchasing symptomatic plants.  If any hosta plants at a store look suspicious there is a chance that nearby healthy-looking plants are infected but not yet showing symptoms, especially plants of the same cultivar or from the same source.  In a home planting, if a plant becomes symptomatic it can be submitted to K-State for testing.  Due to the cost, the homeowner may prefer simply to remove and destroy the suspicious plants.  Dig them up and throw them away or burn them.  The virus is not known to survive in the soil, so when the roots have all decomposed it should be safe to replant hostas in the site.

To submit samples to K-State:

Please send an entire plant if possible (the plant plus pot, or plant plus root-ball).  Place the plant in a plastic bag.  Do NOT add wet paper towels or wet newspaper.  Package in a crush-proof container and send to:

Plant Diagnostic Laboratory
Extension Plant Pathology
4032 Throckmorton Hall
Kansas State University
Manhattan, KS 66506-5504

Hosta Cultivars

HVX has been detected in the following cultivars: (other cultivars are also susceptible)

Before this virus was widely known, some infected plants were thought to be new varieties of hosta and were given names.  All plants with the following cultivar names are thought to be infected:  Breakdance, Eternal Father, Kiwi Watercolours, Leopard Frog, Lunacy, Parkish Gold.
 

References:

Currier S., and Lockhart, B.E.L.  1996.  Characterization of a Potexvirus infecting Hosta spp.  Plant Disease 80: 1040-1043.

HIS Nursery Inspectors Guide

Photos courtesy of J. Appel and B. Hilbert, Kansas Dept of Agriculture

Several more examples of symptoms are available at the following website:

http://www.hostalibrary.org/firstlook/HVXpics1.htm

Web updated 9/01/06
Web comments to jpierz@ksu.edu