Viruses are an unusual entity in that they exist in a gray area between living and non-living. Unless they are attached to a cell, a virus exists as a protein coat with a membrane. Viruses that kill plants attach themselves to the cells of the plant. The virus injects its genetic material into the plant cell, taking it over. As the virus reproduces, its offspring damage or kill an increasing number of cells, causing plant death.
Mosaic viruses include the cucumber mosaic virus, squash mosaic virus, zucchini yellow mosaic virus, watermelon mosaic virus and the watermelon isolate version of the papaya ringspot virus. These varieties attack vine-based crops like squash, gourds, watermelons and cucumbers. Sugarcane and tobacco mosaic virus are plant-specific. You can identify infested plants by a mottling on the foliage that resembles a mosaic. In some cases, the mosaic patterns may also be present on the fruits or vegetables produced by the plant. Mosaic viruses are often transmitted by aphids, but can also be transmitted by various beetles. The best way to control issues with mosaic virus is to plant hybridized varieties that are resistant to the disease. Keeping your garden free of weeds is another way to help reduce the risk of an infested weed supplying the virus to an insect that could later infect a garden plant. Insect control is not an effective way to manage mosaic virus problems, according to Ohio State University.
Peanut Stunt Virus
Peanut stunt virus was first found in Virginia and North Carolina in 1964. A relatively new plant virus, this virus can cause a severe drop in yields both in home gardens and on commercial farms. How much damage the virus causes will depend on when the infection occurs. If the infection is early in the season, the infected plant may never grow more than a few inches high and wide. Although called the peanut stunt virus, this virus affects a number of plants. Crops susceptible to this virus include peanuts, tobacco, soy, clover and snap beans. Leaves on infected plants may curl up and turn yellow. Fruit and produce from these plants are generally small and malformed. Peanut stunt virus generally affects plants that are under stress, such as when lacking water. There is no known treatment or control for this virus.
Bud blight is a virus that is caused by the tobacco ringspot virus. It primarily affects soybeans and can, according to North Carolina State University, reduce yields in home gardens and commercial farms by between 25 and 100 percent. Although most soybeans are grown commercially, some home gardeners plant them to harvest the young beans and pods as edamame. The virus is spread by planting soybean seeds that are infected with the virus. Usually, the percentage of infected seeds is low. Infected plants are very small with brown discolorations on their stems and branches. Leaves on infected plants are smaller than normal and can have a bronze discoloration. The leaves can also sometimes be wrinkled. Buds die and become brown and brittle, hence the name of the disease. The terminal bud often deforms into a crook when this disease is present. There is no treatment for bud blight. The best way to avoid this disease is to always plant high-quality seeds.