Tomato Mosaic Virus Symptoms And Cause

Tomato Mosaic Virus (ToMV) is a fast spreading plant virus that has been around for millennia but was only isolated and identified after the identification of the Tobacco Mosaic Virus (TMV) in the late 1800s.

It quickly devastates a wide variety of crops, most especially tomatoes. In this article, we describe ToMV symptoms and provide sound advice for preventing and treating this plant disease. Read on to learn more.

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Table Of Contents

How Problematic Is Tomato Mosaic Virus?

This type of mosaic virus is very contagious and very serious. To make matters worse, identifying it can be quite difficult. An infected tomato plant may exhibit a wide variety of signs and symptoms depending upon factors such as:

  • Environmental Conditions
  • The Type of Plant
  • The Virus Strain
  • The Plants’ Age

Furthermore, ToMV and TMV are very similar, so it can be hard to distinguish one from the other.

What Are Symptoms of Tomato Mosaic Virus? 

ToMV may attack plants at any growth stage, and the viral disease can become established on any part of the plant. All parts of an infected plant may show signs of the infection.

You may notice a mosaic or mottled appearance on the plants’ leaves. 

Another foliage symptom is leaf stunting.

Plants with very severe infections may begin to take on a fern-like appearance with some areas of the leaves becoming deep green and raised. 

Plants that have been infected with this virus may have reduced fruit set, and the fruit that they do produce may have yellow or dead spots on the exterior and spoiled, brown interior. 

What’s the Difference Between ToMV and TMV?

The symptoms of mosaic viruses are very similar to those caused by several other types of plant disease. Additionally, problems such as lack of minerals in the soil, excessive pollution and herbicide use can cause symptoms similar to those caused by mosaic viruses.

ToMV and TMV affect many vegetable garden and ornamental plants and a wide variety of weeds. Examples include:

Even though TMV and ToMV look quite a bit alike and are quite closely related, they are genetically different. One way to tell them apart is to simply identify the host, but even then, there is confusing overlap. 

Mosaic viruses, in general, tend to infect common vegetable garden plants, such as squash, beans, potatoes and peppers. Additionally, roses and tobacco plants are subject to infection by all sorts of mosaic viruses.

To make matters even more confusing, ToMV negatively impacts garden plants and orchard trees, as well as lots of different weeds, such as lambs quarters and pigweed. Fruit trees (e.g. cherry, pear and apple) are subject to infection by ToMV. ToMV can cause fruit to ripen unevenly.

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How Can You Tell Your Tomatoes Have ToMV?

ToMV causes tomato plants to be stunted with yellowed leaves and reduced fruit production. However, tomato plants may be infected by TMV, and show the same disease symptoms. This variant will also attack cucumber plants and lettuces, in addition to tobacco. 

Affected plants may exhibit:

  • “Brownwall” in which the interior of the fruit turns brown just beneath the skin
  • Spots of necrotic leaf tissue, especially in warm weather
  • Leaves that are mottled deep green and pale green
  • Small numbers of stunted tomato fruit that ripen unevenly
  • Yellow rings on fruit in warm weather
  • Stunted, malformed or curled leaves
  • Generalized stunting and yellowing

Symptoms of ToMV may not be as evident when temperatures are cool, but when weather warms up you may see a sudden increase in the symptoms.

If you are unsure what type of mosaic disease or other disease your tomato plants may be exhibiting, check in with your local agricultural extension. They may ask you to submit a sample of the foliage for testing.

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Florida Division of Plant Industry, Florida Department of Agriculture and Consumer Services, Bugwood.org
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How Is ToMV Spread?

As with all viruses, once ToMV is spread from one plant to another and enters the plant’s system, it replicates and takes over. It’s difficult to control ToMV because it spreads in several ways. 

Dormancy

ToMV can remain dormant through the winter on weeds surrounding the garden plot. The virus can linger in plant debris and in the soil for as long as two years. For this reason, one of the best ways to keep this determined virus under control is to keep weeds cleared and to do away with plant debris promptly.

Pest Insects

During the growing season, pest insects such as:

… spread the virus from plant to plant. 

Human Activity

The ease with which this virus can be spread from plant to plant by simple touching and handling cannot be stressed enough. When you handle infected plants or even brush against them, you can pick up the virus and carry it to another plant.

For this reason, you should be very careful about washing your hands with soap and hot water and disinfecting your tools between plants. It’s important to note that chemicals have a limited effect on the virus. It’s best to boil your tools for a solid five minutes for complete decontamination.

Use of Tobacco Plant Products

If you use tobacco products and the tobacco with which your cigarette or other product was made is affected by ToMV or TMV you can spread the virus through smoke or through physical contact. For this reason, you should always wash your hands after using tobacco products and before working in your garden.

Why Are Your Tomato Leaves Turning Yellow?

graphic showing tomato plant with ToMV - Tomato Mosaic VirusPin

Is It Possible To Cure ToMV?

As with most viruses, there is really no treatment for ToMV. It must simply be contained and controlled as it runs its course.

https://extension.umn.edu/diseases/tomato-mosaic-virus-and-tobacco-mosaic-virus

The bottom line is that all mosaic viruses are incurable and produce very similar symptoms in plants. All should be addressed in the same manner. 

Follow these tips to prevent and control mosaic viruses: 

  • When choosing plants, look for those that are resistant to mosaic viruses. Always purchase seeds that have been certified as disease-free.
  • In addition to removing weeds and plant debris around your garden, take care to control insect pests.
  • Destroy affected plants. If you believe that some of your plants may have been affected by ToMV or any mosaic virus, dig them up and burn them.
  • Replace affected soil. You want to remove not only the affected plants, but the soil in which they were planted. Take care not to plant crops such as cucumbers or tomatoes or other susceptible plants in that area for a minimum of two years.

Questions and Answers On Tomato Care

How Can You Control ToMV?

Follow these tips to keep ToMV under control:

  • Choose disease-resistant varieties. To determine whether the variety of tomatoes you have chosen is resistant to ToMV and/or TMV, look for these initials at the end of the plant name on the seed packet or seedlings that you purchase. [source]
  • Use only seed that has been certified disease-free or use one of these two methods to treat the seed that you purchase:
    • Soak your tomato seeds in trisodium phosphate (Na3PO4) at a 10% solution for a minimum of fifteen minutes.
    • Heat dry tomato seeds to a temperature of 150°F and keep them at that temperature for several (3 – 4) days.
  • Only purchase plants from reputable nurseries. Inquire as to the establishment’s sanitation procedures.
  • Be sure to inspect any plant you plan to buy thoroughly before purchasing. If it shows any symptoms of disease, give it a pass.
  • Always remove all parts of your plants at the end of the season. Don’t leave roots in the ground, especially tomato roots, as this is just inviting trouble.
  • Keep your garden soil watered and mulched. Although ToMV can survive in dry plant debris and dry soil for a couple of years, moist conditions in the soil can reduce this amount of time to as little as one month.
  • Don’t allow tobacco use in or around your garden. This includes cigarettes, chewing tobacco, snuff, cigars, and any other tobacco containing product.
  • Examine your plants frequently and take quick, decisive steps to remove them and sanitize the moment you notice any signs of mosaic virus.
  • Remember to keep your hands and your tools scrupulously clean. If it is not possible to boil your tools, you can use a solution of germicidal bleach diluted to one part bleach and nine parts water. Soak for at least one minute. Alternately, you can make a solution of two parts nonfat dry milk powder and eight parts water to use as a soak. [source]
  • Disinfect everything! Remember to disinfect all garden equipment, such as:
  • Wire mesh
  • Stakes
  • Ties
  • Disinfect as you work. When you are pruning, use two sets of shears. Prune one plant with one set while the other set is soaking in a disinfecting solution. Remember to switch out between plants.
  • Keep potentially contaminated tools separate. If you do discover disease in your garden, designate a specific set of tools to use in that area. [source]

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