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Past Issues

Hosta Viruses

July 18, 2006

The Plant Clinic receives calls about hosta viruses on a fairly regular basis. We have not seen many positive cases of hosta viruses, so possibly the calls are more a function of the media concern than a widespread problem. On the other hand, department of agriculture inspectors in some states reported finding record numbers of hosta virus X (HVX) in inspected sales lots last year, so it is likely that the problem is more widespread than we know. It is good to recognize symptoms to watch for when purchasing hostas.

Several hosta viruses have been reported in scientific literature. These include HVX, tomato ringspot, impatiens necrotic spot, and arabis mosaic virus. Hosta virus symptoms may be subtle or obvious. The most common symptom is mottling of the leaves; but stunting, twisting, ring spots, and puckering may appear. There are many hosta cultivars on the market, and some have odd coloring, odd leaf form, and even some leaf puckering. Be familiar with the cultivar you are purchasing so that you can recognize abnormal symptoms. Plants do not have immune systems, so a virus stays with a plant for life. There are no chemicals that can be applied to rid the plant of the virus. If the hosta is very susceptible, it dies from the viral infection. More resistant plants may be mildly stunted or show symptoms without a growth response.

The image here shows a hosta infected with HVX, a current concern in the hosta industry. The plant on the left is affected; the one on the right, healthy. The infected plant was planted next to the Plant Cllinic building on campus to see how it fared over winter. Interestingly, the plant survived the winter, even with the viral disease present. It has since been removed to prevent spread to other plants. I do not know the cultivar.

The University of Illinois Plant Clinic can identify virus-infected suspects. We cannot positively identify hosta viruses. Virus particles cannot grow on lab media. They cannot be seen with a compound microscope, but they can be detected with specialized enzyme-linked immunosorbant assays called ELISA tests. If symptoms suggest viruses, a private lab offering serological tests is suggested. One lab that can help is AGDIA, Inc., in Elkhart, Indiana. For information on services and costs, go to http://www.agdia.com. There are separate images of hosta infected with arabis mosaic virus, HVX, and tomato ringspot virus on their Web site under “slide show.”

The method of virus particle transmission varies with the virus, so identification is helpful for disease management. For example, HVX is mechanically transmitted through plant sap. You could move it in the garden by pruning an infected plant before a healthy one. Be sure to disinfect cutting tools frequently when trimming or dividing hostas.

Carefully inspect any hostas planted into your gardens. Do not plant those with disease symptoms or those that appear abnormal. Another option is to plant suspicious plants in an isolated location until they prove healthy.