Hosta virus x found in Massachusetts

Hosta virus x (HVX) was first identified in 1996 and has become more prevalent in the nursery trade over the past few years. Several states have reported the virus, and hosta societies are concerned about the disease. In October, Massachusetts reported its first case of HVX at a nursery in Middlesex County. The varieties Sum & Substance, Striptease, and Gold Edger tested positive when sent to Agdia for ELISA testing. The nursery destroyed the infected plants.

HVX is a potexvirus, and, currently, hostas are the only known host. The most common symptoms of hosta virus x are mottled or crinkled leaves. On plants with gold leaves a green mottling, especially along the vein, indicates viral infection. There are several hosta viruses; so, virus testing is the only way to determine which virus your plants have. Hosta varieties can exhibit three different responses to HVX. (1) Susceptible plants will show viral symptoms such as mottling, leaf distortion, leaf desiccation, and poor vigor when infected. (2) Tolerant plants can be infected with the virus but show no symptoms. (3) Resistant plants are not susceptible to infection by HVX. Dr. Lockhart at the University of Minnesota has conducted experiments to determine what category different cultivars fall into. This work was written up in the article “Hosta Virus X: A three year study” in Hosta Journal in 2004. A few varieties are 100% infected with HVX and were selected for their viral symptoms such as interesting streaks, speckles or mottling of the leaf. The varieties Breakdance, Leopard Frog, Lunacy, and Eternal Father are reported as being infected with HVX.

The best way to deal with HVX is to prevent it from entering your nursery stock or garden and using good sanitation. Buy quality, disease-free stock from a reputable dealer. Keep new plants isolated to see if they develop viral symptoms and/or have new lots of hostas tested for HVX. Infected plants may go unrecognized because symptoms can take a couple of weeks, months or years to develop; and some tolerant plants may remain asymptomatic while carrying the virus. HVX is mechanically transmitted via transfer of infected sap; so, good cultural practices prevent spread of HVX. When cutting back or dividing hostas, clean tools and hands before moving to the next plant or block of plants. Deer browsing or a lawn mower blade can also spread HVX; but the virus has not been shown to spread via insects, nematodes, seeds, or pollen.

Once HVX infects a plant there is no cure. The only way to get rid of the virus is destruction of the plant. Hostas can be replanted in the same site, but wait a few weeks to be sure no living hosta material is present in the soil. HVX needs a living host and does not persist in the soil without one. If you suspect you have received plants that may be infected with HVX, testing is available. Commercial flower growers can send material to the UMass Plant Diagnostic Lab for ELISA testing. The cost is $50 per sample. Visit the UMass Floriculture website (http://www.umass.edu/umext/floriculture/grower_services/diagnostics.html) or call the diagnostic lab (413-545-1045) for instructions on sending samples. If you are a homeowner who has a hosta plant you want tested, call Agdia at 1-800-622-4342. Virus testing is expensive but may be warranted if you have a particularly valuable variety in your collection.

Resources:
Beckerman, Janna.2005. The X files: Hosta virus X. University of Minnesota, Yard and Garden Line News, Volume 7, Number 8. http://www.extension.umn.edu/yardandgarden/YGLN-June0105.html. Accessed 6 February 2006.

Blanchette, B. and B. Lockhart. 2004. Hosta virus X: A three-year study. The Hosta Journal. 35(3): 19-23.

Hosta Library website on Hosta Virus X- This site has many photos.
http://www.hostalibrary.org/firstlook/HVX.htm

Kirk, Willie.2005. About hosta virus X. Michigan State University Landscape Alert, Vol.20, No.16. http://www.ipm.msu.edu/CAT05_land/L08-26-05.htm#3. Accessed 6 February 2006.

The pest alert is from the Massachusetts Introduced Pests Outreach Project, a collaborative project between the Massachusetts Department of Agricultural Resources and the UMass Extension Agriculture and Landscape Program aimed at preventing the establishment of new pathogens and pests in Massachusetts. Visit the project website (http://www.massnrc.org/pests) for more information on hosta virus x and other emerging pests or to subscribe and unsubscribe for pest alerts.