TMV is a virus belonging to the Potyviridae family that consists of small rods approximately 700 nanometres long. In an infected plant the youngest leaves develop ring-shaped yellow-green patches, circular shapes and meandering lines. The older leaves develop a yellow mosaic. The leaf turns fully yellow in a short space of time. Sometimes infection happens without the symptoms of the virus being visible.
An attack by mosaic virus occurs mainly in summer and autumn when there are a lot of winged aphids around. Aphids can easily introduce the virus. When you’re working amongst your crops you can also inadvertently spread the virus to a lesser degree. Spreading by seed or in soil is not possible.
The virus has many carriers, including lettuce and various weeds, and can survive in these plants. It also infects other commercial crops including tobacco, cucumber, tomatoes, and so on. Cross-infection is possible (hemp to tomato and visa-versa).
From the moment that the virus enters the plant there is no way to get it back out again; clones from this plant are also now infected with the virus.
Warning: tobacco mosaic virus (TMV) can also be carried in cigarettes and rolling tobacco/shag!!
The effects on the plant are very diverse, and the plant will never recover its previous strength because thanks to the state of the leaves, photosynthesis will remain reduced. The plant will never be a great one, that’s one thing that’s for sure, and in general it will always be underdeveloped.
As said earlier there is no real solution since once it’s in the plant it cannot be got rid of. But the environmental factors are important; a plant in a constant environmental temperature of 21 degrees Celsius or higher will have less trouble from the virus, so keeping your temperature up at this level is essential.
The first step is to make sure you start your grow with a clean space, so make sure it has as few bugs as possible and wash your hands before playing with your plants.
If this virus gets in the mother plant, then there’s a 99% chance that you’ll get it in your grow space too. In principle it is already possible to detect in a clone whether there is viral infection in it. So inspect it carefully. If the plant has any strange features simply discard it and use another one.
In order to slash the chances of an infection you need to start with good clones or take the process of making them into your own hands. You can also choose to grow from seed, which reduces your chance of TMV infection to a minimum.
The big question of course is what’s the cost to your yield? The answer is ‘considerably’. Because your plant has the virus it will make leafage and these will deliver less. If you keep the temperature at 21+ the damage is liveable with, but outdoor plants will have a lot more stress from the infection if you live in a country that tends to have outdoor temperatures below 21 degrees.