Virus Diseases—Beet western yellows, Lettuce infectious yellows, and Lettuce mosaic
Many viruses are difficult to distinguish from one another by symptom alone. In addition, for each particular disease, the symptoms will vary greatly depending on stage of plant at time of infection and other factors. In general, symptoms consist of various leaf and plant deformities, stunting and poor growth, and yellowing or a mosaic or mottling pattern in the leaves. Identification of the particular pathogenic agent can only be made with serological, inoculation, or other laboratory tests.
Buy and plant virus-free seed if available. After symptoms on plants occur, there is no practical control. Reflective mulches or row covers may help prevent infection by aphid- and leafhopper-transmitted viruses. Plants showing symptoms near harvest are edible. Plants that show symptoms early may produce no heads or only small ones.
Plants infected with virus