Tobacco Mosaic Virus

You don’t have to grow tobacco to have reason to worry about the tobacco mosaic virus (TMV). 

Tomatoes are highly susceptible to tobacco mosaic, and the virus can travel on tools, clothing, cigarettes, and, yes, even on saliva and other bodily excretions of cigarette smokers. The tobacco mosaic viruses remain viable after their host dies and can withstand the extreme temperatures of tobacco curing.

Tobacco mosaic virus symptoms on orchid leaves (USDA Forest Service) Public Domain

Tobacco mosaic hosts

In addition to tomatoes and tobacco, the tobacco mosaic virus infects over 350 plant species, including cucumbers and all plants in the nightshade family, as well as many flowers and ornamental plants. While they may not show symptoms, grape vines and apple trees can also become infected.

Symptoms of tobacco mosaic

Tobacco mosaic starts as nothing more than pale green between the veins of young leaves. This lightened area quickly becomes mottled, leaving a green, white, or yellow mosaic pattern. Bumpy wrinkles may also appear, in a behavior known as rugosity, and leaves may appear distorted or stringy. Leaf cupping may also occur. 

Leaf veins may also turn yellow, and you may see yellow streaking on the leaves. Many of these symptoms can be mistaken for signs of chemical overspray, but the mosaic pattern is usually distinct enough to rule this out. While this disease does not kill plants, it can stunt them severely. Infected leaves soon die, leaving dead patches in the plant and reducing production by up to 20%. The fruit that does grow is often discolored and deformed.

How is the tobacco mosaic virus spread?

Unlike many other diseases, which are spread by sap-sucking insects, such as thrips and aphids, the tobacco mosaic virus spreads primarily by direct contact. Chewing insects, such as grasshoppers and caterpillars, may infect plants. And bumblebees may transfer the infection as they pollinate flowers.

Preventing tobacco mosaic virus

Plants infected with tomato mosaic must be removed and destroyed. According to the Michigan State University Extension, you can prevent the virus from moving onto uninfected plants by spraying, just before transplanting, with a 20% nonfat dry milk solution. The milk solution coats the virus, rendering it inactive. The milk treatment only works while wet. You can spray containers, walkways, and other surfaces, as well.

These other tips can also help reduce the likelihood of tobacco mosaic in your garden:

• Quarantine all new plants until you are certain they are pest and disease-free.
• Buy disease-resistant varieties, especially when shopping for heirlooms and hybrids.*
• Wash your hands before working in the garden.
• Wear garden shoes, not street shoes, when working in the garden.
• Avoid taking cuttings from potentially infected plants.
• Employ crop rotation.

*Check plant labels for the letters V, F, N, T, or A. These symbols indicate resistance to verticillium wilt, fusarium wilt, nematodes, tobacco mosaic virus, and Alternaria stem canker.

According to a study by the National Institutes of Health, all the cigarette brands studied tested positive for tobacco mosaic, while only 53% of those viruses were viable. Also, 45% of the saliva samples taken from smokers tested positive for tobacco mosaic virus. So, smokers and users of other tobacco products, please wash your hands before entering your (or someone else’s) garden, and always throw your butts in the trash. Thank you.