We have seen several disease problems on hostas in the past few years, including anthracnose, Sclerotium blight, and foliar nematodes. A few problems have been found in the last few years in Illinois. Fusarium root and crown rot causes leaf yellowing, stunting, rotting of roots, and death of crown tissues. Viruses have been the most troubling to hosta growers. They may cause stunted growth and various odd leaf-color patterns. These include ringspots, mosaic, speckling, and discoloration.
Several hosta viruses have been reported in scientific literature, including hosta virus X, tomato ringspot, impatiens necrotic spot, and arabis mosaic virus. The University of Illinois Plant Clinic can positively identify all of the problems just described except viruses. We can identify symptoms that suggest a virus, but we cannot make positive identification of 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, 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, hosta virus X, and tomato ringspot virus on the Web site under “slide show.” Virus diseases cannot be eradicated from a plant. Usually infected plants need to be removed and destroyed. Transmission varies with the virus, so identification is helpful for disease management.
Carefully inspect any hostas that are planted into your gardens. Do not plant any with disease symptoms or that “look funny.” Beware of reduced-priced plants that you might want to nurse back to health. If purchased, these plants should be isolated until health is regained. Only then should they be planted into the garden.