Pepper Plant Viruses

• Several diseases of pepper plants can cause various symptoms on the peppers themselves, but the only types of diseases known to cause small and misshapen fruit on the vine are viruses. The most common viruses of pepper plants include cucumber mosaic, pepper mottle, potato Y, tobacco etch, tobacco mosaic and tomato spotted wilt viruses. It is sometimes difficult to distinguish between these viruses, since so many share common symptoms. A pepper plant can easily become infected by more than one virus at a time, making accurate diagnosis even more difficult.
  
  

Other Symptoms

• To confirm if your pepper plants have been infected by a virus, look for other symptoms associated with these viruses. Alongside small, misshapen peppers, these viruses cause mosaic, or alternating dark and light leaf spots; mottle, or raised leaf lesions; vein banding, or discoloration along the central leaf veins; and plant stunting, or diminished new growth and overall plant size. The prevalence of these diseases is highly regionally dependent, in the sense that in a given growing area, you are more likely to encounter one or more of these diseases than the other. Therefore, contacting a local university extension office and inquiring as to the most common pepper plant diseases in your area is another useful way to narrow down a diagnosis.
  
  

Preventative Steps

• Due to the destructive nature of these diseases in agricultural settings, many pepper cultivars have been developed specifically for resistance to these diseases, so always plant a diseases-resistant pepper cultivar if one is available to you. Some of these viruses, including pepper mottle, potato Y, tobacco etch and tomato spotted wilt, are transmitted by insects such as aphids and thrips, so insect control is another important way of preventing infection. These diseases also persist in host weeds such as ground cherries (Physalis spp.), nightshades (Solanum spp.), common groundsel (Senecio sp.), wild tobacco (Nicotiana sp.), toadflax (Linaria sp.), sicklepod (Cassia sp.) and jimson weed (Datura sp.), so exercising good weed control around your pepper plants can go a long way in preventing infection.
  
  

Treatment Approaches

• For treating a plant that has already been infected by one or more of these viruses, options are unfortunately more limited. Remove and destroy infected pepper plants, and consider fumigating or otherwise treating the soil in which they were growing before planting any more peppers in the same soil. For serious infections, a chemical fungicide, applied either preventively before symptoms appear or in reaction to an infected plant, can be very effective as well. Simply diagnose the exact disease affecting your pepper plant as accurately as is possible, purchase a fungicide targeted at that specific disease and follow the manufacturer's labeled application instructions exactly.