New Virus Detected in Cannabis: TNV-A Jumps from Tobacco to Hemp

What is TNV-A? The Tobacco Virus That Has Now Infected Cannabis

As legalisation progresses, cannabis cultivation has evolved from being an illicit activity to a more professional crop. This shift entails large-scale operations equipped with all the latest technology.

Proof of this is a recent study conducted in Colombia, where researchers identified the Tobacco Necrosis Virus A (TNV-A) in a Cannabis sativa L. plant for the first time. TNV-A belongs to the Tombusviridae family and had until now been found primarily in tobacco crops and tulips.

Tobacco Necrosis Virus in Agriculture

TNV-A was first identified in tobacco crops in the mid-20th century. Although considered a "limited" virus in terms of the range of plant species it attacks, this silent enemy has steadily gained ground, being detected in crops across Asia, Europe, and America.

One of the features that makes it such a difficult threat to eradicate is its ability to survive in the ground for years and to adapt to new plant species, as has apparently happened with cannabis.

Discovery in Colombia: First Documented Case of TNV-A in Cannabis

This recent study identified the presence of TNV-A, a virus known for causing necrosis (i.e., the death of plant tissue). The analysed plant exhibited symptoms of the disease, such as colour changes in the leaves and the appearance of necrotic areas.

This virus seems to belong to a group called Alpha Necrovirus, a particularly aggressive subtype. In addition, this analysis revealed something interesting: while one of the virus' essential proteins (an enzyme critical to its reproduction) closely resembled that of others in its group, another key protein (the capsid protein that encases the virus) showed much greater variability.

This suggests that, although the internal mechanisms of the virus remain stable, its "outer envelope" can change more easily to adapt to new plant species.

How Has TNV-A Reached Cannabis?

Although it is not yet entirely clear how the virus has infected cannabis plants, researchers are considering several hypotheses, such as cross-contamination via cultivation tools or the presence of the virus in neighbouring plants.

This discovery underscores the importance of stringent hygiene and sanitation measures in professional cannabis cultivation, especially in countries like Colombia where cannabis has already been legalised. It is vital to maintain strict protocols that prevent the spread of plant diseases such as this virus, which, if not properly managed, could spread to other regions through the export of contaminated material.

How Do Viruses Act on Cannabis Plants?

Detecting a virus in a marijuana crop can be more challenging than identifying other diseases like Botrytis, which present unmistakable symptoms. Viruses cause damage that can easily be mistaken for fungal infections, pests, or even nutrient deficiencies.

Furthermore, viruses attack the plant from within, impairing vital functions such as photosynthesis and nutrient absorption. Consequently, growers often don't detect the problem until it is too late.

Added to this is the fact that prohibition policies have stymied cannabis research for decades, making it a race against time for professionals in the sector to stay up to date.

Is It Possible to Detect TNV-A in Cannabis Plants?

Detecting a virus like TNV-A in cannabis is no easy task, particularly in the early stages. However, several visual indicators could serve as warning signs:

• Chlorosis in the leaves: yellowish areas that don't follow typical nutrient deficiency patterns.
• Foliar necrosis: progressive death of plant tissue, seen as brown or black spots on the leaves that may spread from the edges or appear randomly.
• Wrinkling or deformities: leaves grow irregularly, sometimes curling or adopting abnormal shapes and textures.
• Loss of vigour: generalised slowdown in the plant's growth and development.

Unfortunately, these symptoms are not exclusive to TNV-A infection. If you have some experience in growing marijuana, you will know they can also indicate other diseases.

For now, the only 100% reliable way to confirm the presence of this virus is through laboratory tests such as: PCR (Polymerase Chain Reaction) RNA-seq (RNA sequencing) ELISA (Enzyme-Linked Immunosorbent Assay for viral protein detection)

How to Prevent TNV-A in Your Cannabis Grow

Prevention is key to a successful cannabis harvest. If you wish to avoid the incursion of this virus (or any other) into your garden, follow these recommendations:

• Monitor for abnormal leaf morphology and colouring. Immediately isolate any suspicious plants.
• Constantly disinfect your tools (such as scissors) between handling different plants.
• Keep your grow area clean and sanitised - this is essential for avoiding viruses and other potential hazards.
• Control potential vectors of infection such as nematodes and mites, which can carry viruses from one plant to another. Reducing their presence limits disease spread.
• Avoid using clones of dubious origin.
• Implement quarantine protocols when introducing new genetics.

Since there are currently no available treatments, it is crucial to strictly adhere to prevention and disinfection protocols. In the event of an infection, remove or isolate the affected plant (if unsure about the cause) to prevent further spread.

What Are the Implications of This New Study?

This case serves as a wake-up call. As cannabis integrates into the global agricultural system, it is only natural that it faces the same phytosanitary challenges as other commercial crops. The discovery of TNV-A in cannabis should not cause panic, but it should inspire more responsible and proactive disease management practices.

Having access to clear information and implementing proper prevention measures will be key to the success of an industry that continues to expand daily, especially for those investing heavily in large-scale operations and risking significant capital with each cycle.