Grace Anderson, MAg, UM Department of Plant Pathology
Hennepin County Master Gardener
HVX is a plant virus in the Potexvirus group first identified in 1996 by Dr. Ben Lockhart: Plant Virologist, Department of Plant Pathology, University of Minnesota. It is thought to be host specific and is not transmitted by traditional insect fungi or nematode vectors, or via seed or pollen. It is transmitted mechanically through wounds created during propagation or transplanting, or any time sap to sap contact is made through dividing or trimming plants. Vegetative propagation of infected plants, whether by tissue culture or division, will produce infected plants. Once a plant has HVX, there is no cure and it must be destroyed.
HVX reduces plant vigor and destroys foliage appearance through leaf distortion, color bleeding, and necrosis. Symptoms vary among cultivars and may take years to surface, however the likely result is an unattractive and unacceptable foliage plant (Photos 1 - 3). See http://www.americanhostasociety.org/Education/HostaViruses.pdf for additional pictures of these symptoms.
The disease appeared to be widespread and yet little was known about procedures to identify the virus, its methods of transfer, or the existence of resistant varieties. In order to address these issues The American Hosta Society under the leadership of Cynthia Wilhoite (VP Genus Hosta, Indianapolis, Indiana) initiated an effort to obtain research-based, empirical data on the nature and transmission of the virus. Funds were obtained and the research effort was led by Dr. Ben Lockhart.
Experiments were designed to replicate the actions taken by gardeners and growers in maintaining and propagating Hosta. The goals of the experiment were to answer the following questions. Results of the experiment follow each question.
Can HVX be transmitted during normal cultivation?
Virus transmission was accomplished through the use of contaminated tools and by planting in soil containing pieces of infected plant material.
If it can be transmitted in this way, how long is it infective on tools and soil?
Infected plant material kept in the refrigerator remained infective for more than nine weeks. Fresh infected plant material was always infective. Soil with HVX infected plant debris and root material was infective for more than two years.
What practical measure can be taken to eliminate the virus if it can be transmitted by my tools or via infected soil?
All three tested methods of decontamination including, household detergent (Dawn), 70% alcohol solution, and 10% household bleach solution were effective at eliminating infectivity of the virus. The decontamination process required intense scrubbing and cleaning of tools, hands, and pots to remove plant material, soil and sap. It is not enough to simply dip tools in cleaning solution. Tools must be scrubbed free of all dirt and debris.
Is HVX transmission dose dependent?
No difference in infectivity or speed of infectivity was related to dosage of the virus isolate. A significant difference in the rate of infectivity was dependent on the stage of plant growth. The virus was most easily transmitted prior to flowering and when the plant was rapidly growing the spring. We were not able to transmit the virus while the plants were flowering in late summer/fall or dormant.
Are all isolates of the virus transmissible?
Yes, we collected and mechanically transmitted 15 isolates of HVX. The success of transmission was not only dependent on mechanical injury but also on the season in which the contact occurred.
Are there resistant varieties of HVX?
This warrants further study. We were able to infect all Hosta tested under the proper conditions in the field, home garden or greenhouse. At this time, we believe all hosta are susceptible to the virus.
What is the best way to test for the virus?
ELISA testing through Plant Disease Clinics and certified labs is the most reliable method of testing. The new rapid test strips are accurate, reliable, and portable. The strips can be used in the field or greenhouse and will work with leaf or root material.
Strips can be obtained from Agdia, Inc.
What is the best protection against HVX?
Know whether the original sources of plants you buy tests for HVX. Don't be afraid to ask your retail or wholesale source for this information.
For further information on this topic please visit the American Hosta Society.
Grace Anderson recently completed her 23rd year as a Master Gardener in Hennepin County. She is a scientist in the Soybean Pathology Project at UMN and recently received the Master of Agriculture degree in Horticulture at the University of Minnesota. Conducting this research was one of the requirements for receiving this degree.