About 17 viruses have been reported to attack peppers. Those considered economically important in Africa include alfalfa mosaic, chilli veinal mottle, cucumber mosaic, pepper veinal mottle, potato Y, tobacco etch, tobacco mosaic, tomato spotted wilt and chilli leaf curl.
Most of these viruses are transmitted by insects, infected seed and a few by mechanical means. The first six above listed viruses are spread by aphids; tobacco mosaic is mechanically transmitted and infected seed; tomato spotted wilt by thrips; and chilli leaf curl by whiteflies.
Viral diseases are particularly difficult to firmly diagnose by symptoms because there is so much overlap in symptomatology. Furthermore, symptom expression can be altered by many factors among which are cultivar, age of host plant, environmental conditions, host plant nutrition, and viral strains, not to mention the occurrence of virus mixtures. General symptoms include mosaic patterns on leaves, yellowing , ring spots, leaf deformation or distortion, curling of leaves, and/or stunting of plants. They may also cause reduction of fruit size, distortion, and/or ring patterns.
- Plant resistant cultivars, if available.
- Select planting dates to avoid high population of vectors.
- Close plant spacing to compensate for diseased plants.
- Use barrier crops to minimise virus spread.
- Use oil sprays to reduce virus transmission by aphids.
- Use reflective mulches to repel aphids and thrips. For more information on mulching click here.
- Use certified disease-free seed in case of tobacco mosaic virus.