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Tobacco Mosaic Virus

Tobacco Mosaic Virus

Growing a perfect cannabis plant takes a lot of work. There are lighting schedules to perfect, nutrient levels to maintain, and insect infestations to prevent. However, there is one other danger that growers must be aware of, and that is the challenge of viruses.

There are several viruses that can cause severe damage to cannabis plants, and one of the most well known is the Tobacco Mosaic virus. Identified by two scientists in 1892, the tobacco mosaic virus is the first plant virus to have ever been discovered. It devastates the plants it infects and is not picky about the host. Besides infecting tobacco, the plant after which the virus is named, it has been known to infect tomatoes, spinach, eggplant, marigold, eggplant, pepper, and marijuana.

What is Tobacco Mosaic Virus?

Tobacco Mosaic virus is most common in tobacco plants, as the name suggests. It is harmless to humans, but it can devastate a wide range of crops. It prevents plants from growing, making them weak and appear stunted, and can also reduce yield significantly.

The Tobacco Mosaic virus can survive in temperatures as low as 40 degrees Fahrenheit (4 degrees Celsius), which means it can reproduce in almost all growing conditions. Young plants that are infected with this virus tend to look like they have a nutrient deficiency which means many growers miss the first signs that their plant is infected.

Does Tobacco Mosaic Virus Harm Cannabis Plants?

Tobacco mosaic virus can cause significant damage to cannabis plants, such as stunted growth and as much as a 20% reduction in yield. Tobacco Mosaic virus harms plants by inhibiting their ability to process UV light. As the virus progresses, it will penetrate the cannabis plant’s deep vascular system and infect it from roots to the top of the plant.

Once the plant is infected, there is no cure. The only course of action from that point on is preventing the Tobacco Mosaic virus from spreading to surrounding plants.  While the virus will not kill the plant, it can ruin the quality of the buds.

How do Cannabis Plants Catch the Tobacco Mosaic Virus?

Wounded areas of the plant provide the Tobacco Mosaic virus with a point of entry, typically from a branch or leaf breaking or an insect bite location. The wound area can be small enough to be invisible to the naked eye, as the virus only needs to invade one wounded plant cell to take hold. There are several ways that cannabis plants come into contact with the Tobacco Mosaic virus, including the following:


One of the most common aspects of an insect infestation is their ability to transmit diseases to the plants on which they feed. This holds true for the Tobacco Mosaic virus, as many infected plants first came into contact with the virus through insects. While insects are not infected with the virus themselves, they can carry it on their bodies when they move from plant to plant. The most likely insects to transmit the Tobacco Mosaic virus are those that feed on a plant’s leaves.

Seeds and Pollen

Much to the dismay of growers, the Tobacco Mosaic virus can be carried to other plants via pollen and seeds. This means that the virus can linger inside of a grow room, possibly infecting future grows. It is critical for growers to disinfect their growing area thoroughly, as well as their equipment between grow cycles to limit the transmission of this virus, and many other dangerous pathogens.

Soil or Water

Tobacco Mosaic virus can easily survive in water or oil for extended periods of time, so long as the grow room remains above 40 degrees Fahrenheit. It is recommended that growers avoid reusing soil for many reasons, but among them is to limit the transmission of dangerous viruses. When the Tobacco Mosaic virus infects a plant at the roots, it will infect the plant much faster.

The Grower

By far the most common method of transmission of the Tobacco Mosaic virus is through the grower. When growers handle a diseased plant, they are likely to carry the virus on their hands or clothes. Simply brushing against a healthy plant can transmit the virus, so it is easy for growers to do it accidentally.

The Tobacco Mosaic virus can survive on processed tobacco products. Growers who smoke cigarettes and cigars or consume other tobacco products have a greater risk of introducing the virus to their plants.

Signs of Tobacco Mosaic Virus

The Tobacco Mosaic virus is highly infectious, which means growers must be able to identify the virus on their plants to limit transmission to healthy plants. The virus can even lie dormant in some young plants, not showing signs of the virus until they are stressed after being transplanted. Additionally, many growers mistakenly attribute the symptoms of Tobacco Mosaic virus as a nutrient deficiency.

To assist growers in preventing the spread of the this virus check out the most common signs in cannabis plants below.

Discolored Leaves and Stems

One of the first signs that a cannabis plant is infected with the Tobacco Mosaic virus is the appearance of mottled light green or white spots that resemble a mosaic pattern. Leaves may be brown and burnt looking. Additionally, growers may notice yellow or pale green stripes on both new and old growth.

The stems of cannabis plants infected with the Tobacco Mosaic virus may be discolored as well. Typically, the stems will turn a shade of red or purple, and may appear weak.

Deformed Leaves

Besides discolorations, cannabis leaves may have physical deformities. Infected plants may have leaves that curl at the edges or have tips that curve to the side and appear to have a web on them. In hot and dry climates, the lower part of the cannabis plant may weaken and have spots of necrosis.

Slowed Growth

Growers who notice that a few of their plants are progressing much slower than the rest may have a problem with the Tobacco Mosaic virus. This stunted growth will keep the plant from reaching its size potential and will limit root growth. Overall, the plant will appear shrunken, wilted, and weak, with symptoms worsening as the disease progresses.

Reduced Yield

Tobacco Mosaic virus is known to reduce bud size significantly. If growers notice that their buds are not filling out nicely, the virus may be the culprit. Not only will buds look anemic, but they will remain small and produce much less THC and CBD. Once the buds are harvested, growers will notice a less enjoyable taste.

Treating Plants with Tobacco Mosaic Virus

Since there is no treatment or cure for plants with the Tobacco Mosaic virus, growers must focus their energy on preventing their plants from contracting it. Growers who use the following tips have the best chance at avoiding issues with this virus.

Plant Genetics

One of the best steps a cannabis grower can take is to be sure the genetics of the plants they are growing are as strong as possible. Growing plants from seed is the best way to get strong plants, so growers should choose a hearty strain and source their seeds from a reputable cannabis seed bank. This way, plants have their best chance at resisting a Tobacco Mosaic virus infection.


As mentioned above, keeping the grow area clean and sanitized is paramount. The Tobacco Mosaic virus not only lingers in unclean grow rooms, but it can lie in wait on dead plant material. A disinfected and tidy growing area is the best way to avoid infections.

Quarantine and Remove Infected Plants

If growers notice that a plant has the Tobacco Mosaic virus, they must quarantine and remove that plant from the grow area quickly. If the grower suspects a Tobacco Mosaic virus infection but is unsure, they can quarantine it while running tests and continuing to monitor it for signs of an infection.

This virus spreads easily, so removal of an infected plant must be immediate. It is up to the grower if they want to keep the plant elsewhere, but their best chance at avoiding an infection in their healthy plants is to destroy the infected one.

Use Caution

The most important thing growers can do to prevent a Tobacco Mosaic virus infection is use extreme caution when handling their plants. They should be vigilant in cleanliness and checking for infection among their plants. They need to be mindful of what their hands have come into contact with when they handle their plants and be careful to wash their hands frequently to avoid any accidental virus transmission.

Bottom Line

Even though the Tobacco Mosaic virus is one of the most well known plant viruses in existence, there is still no way to treat plants that contract it. Instead, when it comes to the Tobacco Mosaic virus, preventing transmission is the only course of action.

Preventing the transmission of this virus is like preventing any virus that humans can contract. Growers must wash their hands frequently, keep everything clean, sanitize frequently, and isolate sick plants. Armed with the right information, growers can avoid losing a crop to this dvirus.