Peppers - Virus Diseases

Virus Diseases:
      Many viruses infect peppers. Sometimes, plants are infected by a combination of viruses. This, and the variation in symptoms produced as a result of cultivar and environmental differences, make identification of virus diseases by symptoms alone unreliable. A typical virus symptom is leaf mosaic, which is a mottled, non-uniform appearance of color. The pepper mottle virus, which is spread by aphids, causes such mottling [Picture]. Another virus, the Texas pepper geminivirus, which is spread by whiteflies, causes a yellowed, mottled appearance [Picture], in addition to leaf curling and distortion. Viruses can cause stunting; for example, the pepper mottle virus [Picture]. Some of the symptoms caused by the cucumber mosaic virus, which is transmitted by aphids, include vascular and fruit discoloration [Picture] or death of terminal portions [Picture]. The tobacco etch virus, which is transmitted by aphids, can cause mosaic, fruit distortion and stunting, but in the cultivar 'Tabasco', it can cause a lethal wilt [Picture ].

Pepper-infecting viruses can infect other species of plants, often without producing symptoms. These viruses can be transmitted from such plants to peppers by feeding activities of insects such as aphids, whiteflies and leafhoppers. However, vector control is not usually a good strategy for virus control. By the time the vector is noticed on the pepper, the plants are already infected. Once a plant is infected with a virus, the infection can not be cured. If the infection occurs early in the life of the plant, there may be severe yield loss. In areas where pepper viruses and their vectors are endemic, the use of transplants or row covers can protect the plant during the early, critical growing period. Sometimes, cultivars resistant to a particular virus are available. Weed control both within and around a field may help by reducing the available virus reservoirs.

Virus disease diagnosis can be difficult and can require the use of a plant disease diagnostic laboratory. To complicate diagnosis, sometimes agents other than viruses can cause virus-like symptoms. For example, a chimera can cause mosaic-type symptoms on leaves [Picture]. A chimera is a genetic mutation, which occurs rarely, i.e. one plant in a field. Persistent high temperatures (exceeding 100 F) at planting time can injure young seedlings, resulting in distorted foliage [Picture]. Broad mite injury can cause slight [Picture] or severe leaf distortion [Picture ].

See section on Virus Diseases