Tobacco mosaic virus (TMV) is a virus that was first identified in tobacco crops, but can impact other plants, including cannabis. While it cannot hurt the grower, it can significantly deform plants and lower yields. There is no cure. Here is how to spot it and what to do if you have infected crops.

Tobacco mosaic virus, as the name suggests, is a virus common to tobacco plants. TMV causes splotchy and twisted leaves, leaving a strange mottling or mosaic pattern in its wake. It can also slow growth and reduce yields. TMV was the first plant virus to be discovered.

Worse, TMV appears to have spread to other kinds of plants. These include tomatoes, peppers, eggplant, spinach, and marigold. It also appears that cannabis is susceptible to TMV. And although TMV cannot hurt the grower, it can prevent your plants from being successful.

SPOTTING SYMPTOMS

Plants with TMV have a very distinctive look to them. Leaves will be twisted and curved in ways unnatural to the plant. The leaves will also feature yellow stripes, spots, and a strange mottled, mosaic pattern.

Symptoms can be observed on several leaves or on just a few. Some plants are just carriers and never display symptoms themselves. It is also easier to see the leaf mottling if the affected plant is partly in the shade.

Specific visual cues that your plants have been infected with TMV include:

Strange leaf colour: Brown leaves with “burnt” edges, pale or yellow stripes in old and new growth, and dark purple or black patches are one sign. So is the yellowing of the leaves between the veins. A mottled, mosaic pattern is a major mark of TMV.

Stagnation in growth: Both old and new growth can be affected by TMV. If you plant appears not to be growing as it should be, it could be that TMV is slowing it down. Wilting is another possible sign of TMV infection, as is slowed root spread.

Abnormal growth: Leaves grow in a strange, twisted pattern. They also appear webbed, curling under or upwards in odd ways.

Strange Stems: The stems can be either significantly weakened or appear in strange colours like red or purple.

Anaemic buds: Your buds will not get nice and fat, but will stay small.

TREATING INFECTED PLANTS

So far, the incidence of this condition have not been proven - only reported - in cannabis plants. However, the news is not good if you suspect your plant has become infected. There is no cure. An infected plant will have TMV forever. Your main goal, in other words, is to find the infected plants and remove them from the grow. TMV appears to spread via contact. As viruses can also be present in pollen and seeds, they can live for a long time in a grow room. They can survive on grow room equipment, carpets, soil, and dead plant matter.

That is why it is also essential to immediately quarantine and remove any plant you suspect is infected, pronto. Be sure to fully sanitise all grow room surfaces of any TMV traces before starting your next grow cycle.

A NOTE ON PREVENTING INFECTION IF YOU SMOKE

If you smoke cannabis or tobacco, you run the risk of carrying the virus on your hands. As such, it is a good idea to always wash your hands before coming into contact with any plants.