Tomato Mosaic Virus
All plant parts can be affected during any growth stage. The symptoms depend on environmental conditions (light, day length, temperature). Infected leaves show a green and yellow mottling or a mosaic pattern. Younger leaves are slightly distorted. Older leaves show raised dark green areas. In some cases, dark necrotic streaks appear in stems and petioles. Plants are stunted to varying degrees and fruit set may be severely reduced. Unevenly ripening fruits develop brown spots on their surface, and internal, browning blotches in the fruit wall. Crop yield might be reduced significantly.
The virus can persist in plant or root debris in dry soil for periods of over 2 years (1 month in most soils). Plants get contaminated through minor wounds in roots. The virus can spread via infested seeds, seedlings, weeds and contaminated plant parts. Wind, rain, grasshoppers, small mammals and birds can also transport the virus between fields. Bad cultural practices during plant handling favor virus transmission, too. Day length, temperature, and light intensity as well as plant variety and age determine the severity of the infection.
Dry heating seeds at 70°C for 4 days or at 82-85°C for 24 hours will help to rid them of the virus. Alternatively, seeds can be soaked for 15 min in a solution of 100 g/l of trisodium phosphate, rinsed thoroughly with water and dried.
Always consider an integrated approach with preventive measures together with biological treatments if available. There is no effective chemical treatment against Tomato Mosaic Virus.