Hostas are susceptible to several virus diseases that cause a variety of symptoms. Symptoms of virus infection include stunting, ringspots (ring-shaped areas of discoloration), mottling (patchy areas of yellowing), mosaic (alternating patches of yellow and green) and withering of the leaves. Symptoms may vary with the cultivar of hosta and environmental conditions.
Hosta virus X is the most common virus attacking hosta in the Midwest and causes yellowing, mosaic, and death of leaves. It is transmitted on hands or tools that come into contact with infected plant sap. Impatiens necrotic spot virus is another common hosta virus that causes round white spots with concentric rings. This virus is transmitted by thrips.
Tomato ringspot virus causes yellow spots with indistinct edges and is transmitted by root-feeding nematodes. Tobacco rattle virus causes mottling, yellowing, death of plant tissue, and ringspots. It is also spread by nematodes. Finally, arabis mosaic virus is a less common virus disease of hostas. It causes yellow spots or mottling.
Distinguishing between the different virus diseases is difficult based on symptoms alone. In the lab, serological (antibody-based) tests are typically performed to tell the viruses apart.
Management of all virus diseases is similar. Avoid introducing viruses to the landscape by carefully inspecting all new hostas for virus-like symptoms and rejecting those that display ringspots, yellowing, mottling, or other typical indicators of viruses. Plants that are purchased as dormant crowns can not be inspected before planting and so should be obtained only from reputable sources. All viruses can be transmitted when infected plants are used as propagative material, so this should be avoided.
Plants with virus-like symptoms should be removed from the landscape to prevent spread of the virus. Weeds can serve as reservoirs of virus and should be eliminated from hosta beds. Viruses can survive over the winter in the crowns of infected hostas.
Pesticides such as fungicides and insecticides will not prevent or cure viruses. However, insecticides can help to manage insects such as thrips that may transmit viruses. Nematicides can be used before planting hostas to manage some of the nematodes that may transmit viruses, but no nematicides are currently labeled for use on established hosta plantings.
For more information on hosta viruses and other diseases, see the Iowa State University bulletin SUL 14, Hosta Diseases and Pests
Albo marginata hosta leaves showing yellowing and mosaic caused by an unidentified virus.
Gold Royal hosta leaf showing ringspot symptoms caused by an unidentified virus.
This article originally appeared in the 5/11/2005 issue.