Mosaic Virus Symptoms and Treatment

Plants, like humans and other organisms, are susceptible to viral diseases. Likewise, many viruses have also adapted to target specific species of plants.

Mosaic virus is a broad term for a group of plant pathogens that disrupt the normal function of plant cells. This results in leaves with a mottled or mosaic-like appearance.

There are no cures for mosaic viruses once a strain has infected a plant. Proper handling and sanitation are critical in protecting vulnerable plants and keeping an infection under control. 

How Do Mosaic Viruses Work?

A virus operates much like an intruder with a copy of the keys. It binds to a receptor on the plant cell wall and gains access to the cell, where it hijacks the cell’s machinery. The virus reprograms the cell to reproduce the virus instead of carrying out its intended function, leading to cell death and systemic spread throughout the plant.

Infected plants pose a significant risk to surrounding plants. Early detection and removal are essential to prevent outbreaks. Mosaic viruses can spread through leaf-to-leaf contact, grafting, propagation, or wounds caused by insects, mechanical damage, or weather. These viruses can survive on contaminated hands, plant debris, gardening tools, and even clothes, making stringent sanitation practices crucial.

Symptoms

Healthy plants typically exhibit dark green or lush green leaves. However, mosaic virus symptoms include blotchy light and dark green or yellow mottling on foliage, leading to distorted leaves. Due to the compromised function of these leaves, they may drop, stunting plant development.

Additional symptoms include small, misshapen leaves and flowers, brown streaks on flowers, and unevenly ripened or discolored fruit. The specific symptoms of mosaic virus can vary depending on the strain and the host plant species.

Common Strains

There are hundreds of strains of mosaic viruses not genetically related to each other. Many of these strains cause considerable economic damage to farmers and have names including the infamous Tobacco Mosaic Virus, Cucumber Mosaic Virus, Rose Mosaic Virus, Cowpea Mosaic Virus, and Pepino Mosaic Virus, just to name a few. 

Tobacco Mosaic Virus

The tobacco mosaic virus is one of the most studied of all mosaic viruses and is the first virus to be purified in the late 1800s. It transmits viral RNA within a rod-shaped virus particle (virion) and can infect a variety of edible and ornamental plants, including tomatoes, peppers, lettuce, and cucumbers.

These plants can also be affected by other types of mosaic viruses so it’s not possible to diagnose the specific type of virus without sending samples to a lab. Tobacco mosaic virus is persistent and can linger in infected soil without a host and survive hot temperatures. Resistant tomato varieties are available, often denoted with “TMV” in seed catalogs.

Tomato Mosaic Virus

Tomato mosaic virus (ToMV) is another significant threat to tomato growers. Like TMV, it can spread through contact with healthy plants. Resistant varieties are marked with “ToMV,” and researchers continue to develop transgenic plants to improve resistance. Infected plants transmit the disease upon contact with healthy plants. In addition to tomatoes, this strain also affects many other plants. 

Cucumber Mosaic Virus

The cucumber mosaic virus (CMV) is a disease found around the world that affects over 1200 plant species. In addition to mottling on the leaves, an infected plant might also exhibit ring spots on leaves and fruits. This virus is seed-borne and spread by aphids, making it one of the more challenging strains to control.

Control

Start your garden off right by purchasing virus-free seeds or seedlings from certified distributors. Infected plants should not be composted because the virus can persist in the soil for years.

Disinfecting gardening tools or farming equipment is important in controlling the spread of a number of viral diseases. Viruses can also be transmitted to new host plants through minor insect wounds. For example, aphid vectors or thrips can exacerbate the spread of the disease.

Using a floating row cover can be an effective way to create a physical barrier around susceptible plants. As with other viral diseases, antibiotic or antifungal treatments would not work. 

Frequently Asked Questions