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Mosaic Viruses: How to Control and Prevent Mosaic Viruses | The Old Farmer's Almanac

Mosaic Viruses

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How to Identify, Control, and Prevent Mosaic Viruses

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Here are tips on how to identify, control, and prevent mosaic viruses on a variety of plants.

What Are Mosaic Viruses?

Mosaic viruses affect more than 150 types of plants, including many fruits, vegetables, and flowers. The disease is characterized by leaves that are mottled with yellow, white, and light or dark green spots and streaks (in other words, a “mosaic” of these colors). Some of the most commonly infected plants include tomatoes, squashes, cauliflower, and cucumbers, but many more plants are susceptible.

Types of Mosaic Viruses

There are a number of mosaic viruses that commonly affect plants in the vegetable garden, including:

  • Bean Common Mosaic Virus (BCMV) and Bean Yellow Mosaic Virus (BYMV) are the primary mosaic viruses that affect beans of all types. They are typically spread by aphids, but BCMV is also seed-borne, so do not save seeds from infected plants. 
  • Cucumber Mosaic Virus (CMV) is one of the most common types of mosaic viruses and tends to be spread by aphids. As can be inferred from its name, cucumber mosaic virus often affects cucumbers, but it is also a common problem for many other garden plants, including other cucurbits (melons, squashes), nightshades (tomatoes, peppers, eggplants, potatoes), and leafy greens (lettuce, spinach).
  • Tobacco Mosaic Virus (TMV) spreads through seeds and direct contact, and the best way to avoid it is to grow resistant varieties. 
Identification

How to Identify Mosaic Viruses and Damage

Viral diseases are difficult to identify because symptoms vary from plant to plant and may also vary depending on the age of the plant and its growing conditions. However, the most common ways of identifying mosaic viruses are listed below.

  • The leaves are mottled with yellow, white, and light and dark green spots, which appear to be elevated. This gives the leaves a blister-like appearance.
  • Plants are often stunted, or they grow poorly.
  • Plants may have other deformities and their leaves may be crinkled or wavy. 
  • Cucumber mosaic virus: Infected plants are stunted and often exhibit “shoestring sydrome,” which is a characteristic malformation in which the edges of the leaves fail to develop, with the leaf veins developing as long, narrow strips. Tomatoes are small and misshapen.
  • Tobacco mosaic virus: Infected plants have mottled and yellowed leaves and twisted or deformed young growth.
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Photo Credit: University of California. Cucumber mosaic virus causes severe damage and discoloration to a spinach plant.
Control and Prevention

How to Control Mosaic Viruses

Once plants are infected, there is no cure for mosaic viruses. Because of this, prevention is key! However, if plants in your garden do show symptoms of having mosaic viruses, here’s how to minimize the damage:

  • Remove all infected plants and destroy them. Do NOT put them in the compost pile, as the virus may persist in infected plant matter. Burn infected plants or throw them out with the garbage.
  • Monitor the rest of your plants closely, especially those that were located near infected plants.
  • Disinfect gardening tools after every use. Keep a bottle of a weak bleach solution or other antiviral disinfectant to wipe your tools down with.

How to Prevent Mosaic Viruses

  • Plant virus-resistant varieties in your garden. Resistant varieties of tomatoes have yet to be developed for cucumber mosaic virus, but tomatoes that are resistant to tobacco mosaic virus may have some slight resistance to cucumber mosaic virus as well.
  • Mosaic viruses are mostly spread by insects, especially aphids and leafhoppers. You can try covering your plants with a floating row cover or aluminum foil mulches to prevent these insects from infecting your plants. Look at our other tips for controlling aphids.
  • Control your weeds. Some types may serve as hosts for the disease, and when aphids and other insects feed on these plants, they will spread the viruses to your garden plants.
  • To avoid seed-borne mosaic viruses, soak seeds of susceptible plants in a 10% bleach solution before planting.

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