The presence of Hop Latent Viroid in cannabis has been a hot topic in the cannabis community for the past few years. This particular viroid has many acronyms, including HpLVd, HLV, and HLVd, but for our purposes, I will abbreviate it as HLVd.
HLVd is a great concern to cultivators and the cannabis industry as a whole because it can greatly impact cannabis quality and yield. In this article, I will explain Hop Latent Viroid and the resulting “Dudding Disease” and give advice on how to identify symptoms of infected plants. I will also explain how HLVd spreads and how to test and rid your garden of the viroid. By being vigilant and well-educated on the topic, you will be able to keep your garden free of plant pathogens and prevent an unfortunate outbreak.
What is Hop Latent Viroid?
HLVd is commonly mislabeled as a virus but is actually a viroid. Viroids, like viruses, are made of nucleic acid but lack the protein shell that viruses have. Viroids are much smaller than viruses, but like viruses, they are not living organisms. Viroids are single-stranded genetic material that cause a systemic infection in living things. HLVd was first diagnosed in hop plants (hence the name), which share the same family as cannabis. HLVd was first diagnosed in cannabis five years ago, but the symptoms of the resulting Dudding Disease were seen in cannabis years before it was known to affect cannabis crops.
What causes “Dudding disease”?
During an HLVd infection, the viroid starts altering the plant’s DNA, causing what many people call dudding or cannabis stunting disease. Much like how HIV can lead to AIDS in humans, HLVd leads to these other greater health problems in plants. When the viroid infects the plant, it moves systemically throughout the organism and starts replicating.
HLVd replicates quickly; symptoms become more apparent as the pathogen load increases. A plant won’t even appear to be infected with a low load. However, after any stress event such as drought, heat stress, or physical damage to the ‘healthy’ plant, HLVd will be opportunistic and start replicating at an alarming rate, and symptoms will become apparent much sooner.
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What are the symptoms of HLVd or Dudding disease?
There are many Hop Latent Viroid symptoms (like the resulting Dudding disease) to look out for in your garden. Being able to identify these symptoms early on will help you be able to hopefully get rid of plants infected with the viroid and help save the rest of your healthy plants.
The most obvious symptom is stunted and irregular growth of the HLVd-infected plants. A 90-degree branching habit often forms on infected plants and is a tell-tale sign of infection.
Other symptoms to look for later in flower are underdeveloped, smaller flowers on your plants. The flower’s scent may also be less potent when a plant is infected, and they don’t fully develop their color on strains that tend to turn shades of purple.
The cannabis plant in the forefront is infected with HLVd. The plant looks underdeveloped compared to its peers. Her leaves haven’t fully turned purple, and many of her pistils remain white, which, this late in the flowering stage, can be a sign of late HLVd infection.
However, some plants can remain asymptomatic and not show these symptoms while being initially infected with the viroid.
How do plants get HLVd, and how does it spread?
HLVd infects plants through many different vectors. Once infected, it starts altering its DNA. This causes the symptoms and damage we associate with the Viroid and resulting Dudding disease.
Hop Latent Viroid is mainly spread through mechanical transmission, basically defined as physical contact. This type of transmission happens during tasks such as pruning, defoliating, cloning, and trimming. Any time you create an open wound on a plant, there is a chance for the viroid to possibly affect your plants. Typically, HLVd is spread on unsanitized scissors and gloves, so developing good sanitation habits is crucial to stopping the spread of HLVd in your garden.
This very first marijuana plant on the table shows early signs of stunting associated with HLVd. You can see how the other plants have more leaves and have bushier, more healthy-looking growth compared to the infected plant.
Hop Latent Viroid spread is also caused when infected water is shared among plants in certain hydroponic systems.
Hop Latent Viroid can also be found in root tissue, so growers who reuse their potting soil could transmit the viroid by reusing the soil of an infected plant. Your first line of defense against the viroid is being able to spot the symptoms. Early detection can prevent cross-contamination from infected plants to healthy ones.
Here’s our guide on: Bacterial and fungal controls for marijuana plants, if you are worried that you may have another disease on your plants.
Can I test my cannabis plant for HLVd?
The only way to be 100% sure a plant is infected with HLVd is through genomic testing. There are many different services and hop latent viroid testing kits available. They usually involve leaf and root hair sampling.
Root hair sampling seems to be the most effective way to test for HLVd since there tends to be a higher concentration of the viroid in root tissue than in leaf samples. When a plant tests positive for HLVd, there is not much you can do to save it.
A good side-by-side comparison of an infected weed plant next to a healthy one. The plant on the left shows signs of infection such as 90-degree branching, irregular growth, and underdeveloped flowers.
How do you get rid of HLVD in cannabis plants? Is there a cure?
As of now, there is no definitive Hop Latent Viroid cure. However, there are steps you can take to treat Hop Latent Viroid contaminated equipment and spaces to prevent further spread.
Multiple people are working on products that can possibly remediate the viroid but only to a certain point. From what I have seen, these products can lower the pathogen load within a plant and possibly keep the load below a threshold where you will not see the effects of dudding disease in your flowering plants. Due to HLVd’s mode of infection, there currently is no definitive product to cure the viroid. But, at ILGM we do sell mold resistant seeds so that you can avoid diseases and issues ahead of time!
There are also experimental methods from traditional agriculture that remediate plants with HLVd. Some techniques, such as cryotherapy, thermotherapy, and root tip micrografting, are being explored, but the efficacy of these treatments is questionable for cannabis. One promising method is meristematic tissue culture. However, this type of propagation requires an extremely sterile space and very expensive lab equipment. It is also a very long and tedious process that requires extreme accuracy and attention that most of us don’t have time for in our personal lives.
For more information about symptoms in infected cannabis plants, check out the video below, which is made by Professor Debacco from the University of Connecticut. In the video he clearly explains which symptoms are present in plants when they are infected by the Hop Latent Viroid (HLVd).
Matthew DeBacco is a Professor of Agronomy (MS) as well as Plant Pathology and Horticulture (BS), who teaches several courses on the Horticulture of Cannabis at the Department of Plant Science and Landscape Architecture at the University of Connecticut.
Be sure to like and subscribe to his channel: https://www.youtube.com/@DeBaccoUniversity
With cannabis becoming more widely legalized, more tissue culture labs are popping up worldwide. One day we may be able to take a plant to a lab and have them take your prized cultivar infected with HLVd and remediate it for you. A few labs in the USA offer services like this but only at a commercial scale. For home growers, there are no viable cures as of yet. Your only option is prevention.
If you want to learn how to properly keep your marijuana plants healthy, check out our Grow Bible by Robert Bergman!
Final thoughts and tips on HLVd
By increasing your efforts to keep equipment and your garden clean and sterile, your chances of spreading Hop Latent Viroid and other pathogens drastically decrease. With so many pathogens that damage cannabis plants, such as Botrytis and Powdery Mildew, there’s already plenty to worry about. Plus, new pathogens, like the recently discovered Citrus Yellowing Vein Associated Virus (CYVCV) and Beet Curly Top Virus, add to the list.
The left image shows a plant with ‘Citrus Yellowing Vein Associated Virus’ next to healthy plants. The right image shows a close up of said plant.
That’s why it is more important than ever to stay vigilant as growers if we want to keep our gardens happy and healthy.
Used sources for this article
University of Connecticut. (2021). Prof. Matthew Debacco. Retrieved October 19, 2023, from https://cannabis.cahnr.uconn.edu/matthew-debacco/
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