Many viruses are difficult to distinguish from one another based on symptoms alone. In addition, for each particular disease, symptoms will vary greatly depending on stage of plant at time of infection and other factors. In general, virus symptoms consist of various leaf and plant deformities, stunting and poor growth, or yellowing or mosaic or mottling pattern in the leaves. Leaves may be crinkled or wavy. Dry, corky areas or necrotic streaks may be present. Identification of the particular pathogenic agent can only be made with serological, inoculation, or other laboratory tests.
Life cycle
For the most part, mosaic viruses that infect potatoes are transmitted by aphids. They feed on the sap of infected plants and transmit the virus to healthy plants. Nearby weeds may also serve as alternate hosts for the virus. Potato tubers are probably the primary overwintering reservoir of these viruses. Other viruses with no known insect vector may be carried in tubers and transmitted mechanically by machinery, root-to-root contact, sprout-to-sprout contact, or seed-cutting equipment.
Solutions
Control weeds as some may serve as alternate hosts for virus. Buy and plant virus-free seed or seed tubers. Some varieties may show resistance. After symptoms on plants occur, there is no practical control. Reflective mulches or row covers may help prevent infection by aphid-transmitted viruses. Plants showing symptoms near harvest are edible.
