How to Protect Your Cannabis from Hop Latent Viroid?

Who knew cannabis plants could also go through pandemics as we did, but here we are. Cannabis does go through something similar to a pandemic: hop latent viroid. It's a condition that affects many cannabis plants, resulting in stunted growth or low-quality yield.

Learn what hop latent viroid is, how it spreads, how you can identify it, and how to prevent and deal with it in your cannabis garden. Here's everything you need to know about the hop latent viroid in cannabis plants. 

What is Hop Latent Viroid?

Image Credit - Greenhousegrower

Commonly mislabeled as a viroid, hop latent viroid is actually a type of viroid. Before looking into this infection, let's take a look at what viroids are and how they are different from viruses. 

Viroids and viruses are similar in the sense that they are both made of nucleic acid and are non-living organisms that can cause infections in living organisms. Apart from that, they are quite different. Viroids are the smallest known non-living organism that can spread infections; they can be up to 80 times smaller than the smallest viral genome! Another major difference between the two is that viruses have a protein shell that viroids lack. 

Hop Latent Viroid Studies

In the late 1980s, experts at the Institute of Agronomy and Food Technology (Spain) found a viroid-like RNA in a couple of hops varieties in the Leon region of the country. This RNA seemed to be asymptomatic at first, so they named it the hop latent viroid (HLVd).

However, further studies on the crop in the United Kingdom found that this RNA only appeared asymptomatic, but it was capable of affecting the plant in many ways. Experts found HLVd could significantly affect the yield, essential oil content, and α-bitter acid content in the crop. 

Research on HLVd in relation to cannabis has focused on several aspects, such as detection methods, transmission, symptomatology, and potential management strategies. Here are a few findings that throw some light on the studies conducted on HLVd and cannabis:

• Detection Methods: Some researchers have come up with sensitive molecular techniques, such as reverse transcription polymerase chain reaction (RT-PCR), to detect the presence of HLVd in cannabis plants. These methods help in identifying it early and monitoring the viroid, thereby allowing growers to take appropriate measures to prevent its spread.
• Transmission: HLVd can be transmitted through infected plant material, such as cuttings and seeds. Studies have shown that vertical transmission (from mother plants to offspring) is also possible, which means the viroid can persist in subsequent generations. Additionally, vector-mediated transmission through insect pests, such as aphids, has also been suggested but requires further investigation as it's not backed by solid evidence.
• Symptomatology: HLVd infection in cannabis plants can lead to various symptoms, including stunting, leaf chlorosis (yellowing), leaf distortion, and reduced yield. However, the severity of symptoms may vary depending on factors such as viroid strain, host genotype, and environmental conditions.
• Viroid Variability: Different strains or variants of HLVd have been identified in cannabis plants. These variants may exhibit variations in symptom expression, pathogenicity, and prevalence across different geographic regions. Understanding viroid variability is crucial for developing effective control strategies.
• Management Strategies: While eradicating HLVd from infected plants completely is challenging, several management strategies have been proposed. These include the use of certified disease-free plant material, quarantine measures to prevent the introduction of infected plants, and sanitation practices to reduce viroid transmission. Additionally, genetic resistance through breeding programs and RNA interference (RNAi) technology are being explored as potential avenues for HLVd control.

While scientists are still studying this RNA-based species, not much is known. And since this is an active area of study, we may know more about it in the future. 

Hop Latent Viroid and Cannabis

If your cannabis plant suffers from a hop latent viroid, it can produce similar results. At first, you may attribute your plant's reduced or poor-quality yield to genetics, but HLVd would be the reason behind those problems. 

When cannabis suffers from HLVd, the viroid alters its DNA, which leads to the cannabis stunting disease, aka dudding. This is when the viroid doesn't produce direct symptoms but affects the plant's health and leads to other health issues. And it moves systematically through the plant before replicating. 

We already know how viruses replicate quickly, and viroids are no different. Once they find a host in your plant, they start replicating at an amazing speed, and the symptoms start showing up as the viroid increases in number. This usually occurs after your plant has experienced any kind of stress that may compromise its immunity, like damage, heat stress, drought, or other diseases. 

Transmission of HLVd in Cannabis

Not a lot is known about the hop latent viroid, but experts have found some evidence that hints at how the viroid spreads from one plant to another. So far, studies have shown that this viroid tends to spread via mechanical transmission through contaminated tools or equipment. This can occur during pruning, cloning, trimming, or defoliation — any time you wound your plant. 

Primarily, the transmission can occur through infected plant material like cuttings, for example, but it can also happen through seeds. However, the exact routes of transmission are still being studied. Here are a few ways the transmission could occur:

1. Vertical Transmission: HLVd can be transmitted from infected mother plants to their offspring through seeds. This vertical transmission is one of the main sources of HLVd infection in cannabis. The viroid can be present in the seed coat, embryos, or other parts of the seed, allowing the infection to be carried over to the next generation. Researchers have also found that HLVd is quite effective at transmitting through clones. So, if you take clone cuttings from an infected mother plant, around 10% to 30% of the clones will also be infected and exhibit symptoms of HLVd.

• Horizontal Transmission: HLVd can also spread horizontally between plants through various means. While the exact mechanisms of horizontal transmission in cannabis are not yet fully understood, studies suggest the involvement of vectors, mechanical transmission, and potential transmission through pollen.
• Vector-Mediated Transmission: Insects, particularly aphids, have been considered potential vectors for HLVd transmission. Aphids can feed on infected plants and acquire the viroid, which they can then transmit to healthy plants during subsequent feeding. However, the extent to which aphids or other insects contribute to HLVd spread in cannabis remains a topic of ongoing research.
• Mechanical Transmission: Mechanical transmission can occur when you prune or trim the plant or anything else that involves physical contact with infected plant material. Tools, equipment, and hands can be mechanical agents for HLVd transfer between plants. Hop latent viroid can also occur due to infected water, especially in a hydroponic setup that shares the same water among many cannabis plants. Additionally, experts have also found HLVd in root tissue, so if you recycle your old soil and it's not done properly, your next batch of plants can experience an HLVd infection. 
• Pollen-Mediated Transmission: There is some evidence to suggest that HLVd may be transmitted through pollen. Infected male plants could release HLVd-contaminated pollen, which, upon reaching receptive female flowers, could potentially introduce the viroid into the developing seeds.

Note that the transmission routes may vary depending on various factors, including the prevalence of HLVd in the cultivation region, cultural practices, vector presence, and the use of infected plant material. It is important for you to understand the dynamics of transmission to implement effective control measures and prevent the viroid from spreading. 

How to Spot Hop Latent Viroid in Cannabis?

When experts first discovered hop latent viroid, they thought it did not affect the hop plant in any way since it did not show any symptoms. However, later it was discovered that HLVd was indeed a dangerous viroid that caused indirect symptoms in the plant. 

This is the same challenge that many new growers face with their cannabis plants when they suffer from HLVd. At first, if the plants don't grow healthy or show symptoms, they are attributed to things like diseases, genetics, stress, environment, etc., but growers seldom know that the symptoms can be caused by the hop latent viroid. 

Additionally, what makes the problem worse is that hop latent viroid tends to stay dormant for a long time until the plant experiences stress, which causes the viroid to suddenly wake up and start multiplying. This is the reason HLVd has spread to thousands of plants globally without their growers even knowing about it. 

These factors make it difficult for you to identify this viroid in your cannabis plants, but there are some subtle signs that you must look out for. Being able to identify these signs will help you take the right steps to protect your cannabis plants. 

The primary and most obvious symptom of the hop latent viroid is stunted or irregular growth, due to dudding. Another common symptom is the growth of branches at a 90-degree angle from one another. 

Apart from the obvious symptoms, the hop latent viroid can also exhibit other symptoms, both during the vegetative and flowering stages. So, here are the common symptoms:

• Stunting: Infected cannabis plants may exhibit reduced overall growth and stunted development compared to healthy plants. This will be particularly evident in younger plants during the vegetative stage.
• Leaf Chlorosis or Yellowing: It's easy to misunderstand that your plant may be suffering from nitrogen deficiency; however, plants affected by HLVd may also display chlorosis or yellowing of leaves. The chlorotic areas are often irregularly shaped and can vary in intensity, ranging from pale yellow to a more pronounced yellow or white coloration.
• Leaf Distortion: The leaves will appear distorted. In addition, they may exhibit curling, cupping, or twisting, resulting in a deformed appearance. The severity of the distortion can vary from mild curling to more pronounced and dramatic leaf malformation.
• Reduced Yield: HLVd-infected cannabis plants may experience reduced yield or lower quality of the harvested buds. The impact of the viroid can vary depending on the severity of infection, timing, and other environmental factors.

In addition, you can see other symptoms in your plants, broken down by their growing stage:

Symptoms of HLVd during the vegetative stage:

• Smaller spaces between the internodes
• Plant not growing tall enough 
• Reduced vigor 
• Smaller leaves than expected 
• The stems may be brittle 

Symptoms of HLVd during the flowering stage:

• Underdeveloped or smaller buds 
• The buds may not smell as strong as you would expect from the strain 
• The buds may not develop their full color
• The buds may also grow hairy or loose 
• Low trichome production on the buds 
• The yield could be 50% less potent 
• The overall loss in the quality and quantity of yield 

You must also note that not all cannabis plants that suffer from HLVd exhibit these symptoms; some plants tend to stay asymptomatic for a long time. 

Once you glance at these symptoms, it's easy to chalk them up to bad genetics, poor growing conditions, or other problems. But if you know your plant is not supposed to perform like that and have taken the right steps for healthy growth, your plant may be suffering from HLVd. 

Know for Sure by Testing Your Plant

Unfortunately, the only way to know for sure if your plant is suffering from HLVd is to opt for genomic testing. You can either send a sample to a nearby lab or order a hop latent viroid testing kit; the latter is available in online stores and are not so expensive. 

Most of these tests use leaves or root hair as samples, but the latter is the most reliable sample for HLVd testing. This is because HLVd tends to collect in the root tissue in higher concentrations than in leaves. 

What to Do If Your Plant is Suffering from Hop Latent Viroid?

Image credit - moderncanna

If you suspect your cannabis plant suffers from hop latent viroid, you must act quickly. The first step is to determine if the plant is actually suffering from hop latent viroid and then take the right steps to ensure the viroid does not spread to other plants in your garden. Follow these steps if you think there's an HLVd infection in your cannabis plant.

1. Screen the Plant First

The fastest and most effective way to determine if your cannabis plant is suffering from HLVd is to screen it. As mentioned earlier, you can contact your nearby lab and ask for a qPCR test, but depending on where you live and your budget, this may not always be the best option. A lab test is only recommended for commercial growers. For small cannabis gardens, a lab test is an overkill, so you should instead get a hop latent viroid testing kit off the internet. 

2. Isolate the Plant 

If your plant is infected with hop latent viroid, you need to isolate it immediately so it does not spread the infection to other plants. So, you must remove the plant from the garden and place it in quarantine (or toss it in the bin). In any case, you should also test other plants in your garden, especially if you've used the same tools on them or if they have come in contact with the infected plant in any way.

3. Use Tissue Culture 

If all your cannabis plants are suffering from HLVd or your mother plant is infected, you can use tissue culture to get rid of HLVd. Tissue culture uses a special treatment that removes the viroid, so the next batch of plants can grow healthy. 

Tissue culture is an advanced method that involves certain chemicals that kill the viroid and help you grow healthy plants, but this method is laborious and time-consuming. So, it is only recommended for commercial growers whose business relies on plants that are infected, like a special mother plant. 

4. Use an Alternative Treatment 

HLVd infects thousands of plants across the world, and since most cannabis growers want to get an easy cure for it, they have been experimenting with various treatments. One of them is showing promise, so you can try that to get rid of HLVd in your cannabis plant. Remember, there is no scientific evidence backing this treatment, so it may or may not work for you. 

Follow these steps:

1. Take 8 mp of any broad-spectrum fungicide or bactericide 
2. Mix the fungicide or bactericide with a liter of water 
3. Dunk a fresh clone cutting into the mixture for a few minutes and plant it as usual 
4. Once they root, again dunk the clone in a mixture that contains 0.5 ml of the fungicide or bactericide mixed in a liter of water

Try this for your plants, and let us know how it goes. 

5. Toss Your Plant 

If you aren't interested in cloning and tissue culture, the next best solution is to toss the infected plant and start again. Yes, this sounds harsh, but it is the only way to ensure your other plants don't get infected by HLVd. Sometimes, it's better to just cut your losses. 

6. Disinfect Everything

As mentioned earlier, HLVd can spread via contaminated tools and equipment, including the soil. So, you need to start disinfecting everything that you use in your cannabis garden — from the soil to the pruning scissor, everything! 

You can use basic disinfectants to disinfect the tools and pieces of equipment. As for the soil, while you can recycle the soil, it would still be a better option to replace it. Yes, it does sound like a hassle, but it guarantees that the same viroid will not transmit to the next batch of cannabis in your garden. 

Is There a Cure for Hop Latent Viroid?

Tissue culture can fix the issue and help you save the good genetics of the mother plant, and alternative treatments are a hit or a miss. Unfortunately, there is no other definitive cure for hop latent viroid. 

Many experts and growers are working to find a cure, but even the remedies that are currently in use, like the one mentioned above, don't cure the issue entirely. Such treatments only ensure the pathogen load in the plant stays below a point where it does not induce dudding (or other symptoms) in the cannabis plant. 

Experts are also experimenting with other traditional agricultural practices, like thermotherapy, root-tip micrografting, and cryotherapy, to see if any of them can cure HLVd, but the studies are still in their infancy, and we must wait for any substantial outcome. 

Meristematic tissue culture is promising, but right now, this method is expensive and requires a super sterile lab, so it is not the ideal solution for most growers. But there is hope with more and more countries legalizing cannabis and more tissue culture labs being set up worldwide. 

The day isn't far where if your favorite mother plant is suffering from hop latent viroid, all you have to do is take it to your nearest lab, and they will remedy the situation for you. Some labs are offering this already, but again, their services are super expensive and only aimed at commercial growers. 

How to Prevent Hop Latent Viroid While Growing Cannabis?

Image credit - Dudegrows

In 2021, a group of experts from a cannabis nursery conducted over 200,000 tissue tests on cannabis plants in California. The study found that approx. 90% of cannabis facilities tested positive for hop latent viroid, and according to the experts, around 30% of the plants in each facility exhibited symptoms of HPVd.

Considering how common hop latent viroid is in cannabis, it is crucial that you take the right steps to prevent this viroid from ever infecting your cannabis plants. So, here are some of the best tips on managing and preventing HLVd in cannabis plants. 

1. Start with Good Genetics

The first step in preventing HLVd in your cannabis is to start with good genetics. This viroid can transmit genetically, so you need to choose high-quality seeds that are certified and healthy or take clone cuttings from healthy mother plants that are not suffering from HLVd or any other diseases. 

So, always purchase seeds from reputable seed banks that offer an in-depth chemical analysis of the seeds along with all the other crucial information you need to know about them on the product page itself. 

2. Test Everything that Comes into Your Garden

According to the review authors of the aforementioned study, an important step in preventing hop latent viroid is to test all cannabis plants that you bring into your garden, whether it is via seeds, grown plants, or clones, along with all the propagative tools or equipment. 

You can test the plants with hop latent viroid testing kits as they are cheap and easy to use, and even if the tests come negative, you must quarantine every new plant for at least 30 days. Here, you can also test your plants in the third week of quarantine for more accurate results. 

3. Test Your Plants Regularly

Testing does not end when you bring the plants into your garden. In fact, you must test your plants regularly for HLVd (or any other disease, for that matter). This way, you can spot any problems earlier and take immediate action before it has spread to other plants. 

4. Disinfect Your Tools 

You should also disinfect your tools properly since one of the primary ways hop latent viroid transmits to other plants is mechanical. One of the most effective ways of disinfecting your tools is using a 70% isopropyl/ethanol solution. However, you can also use a 10% bleach solution to disinfect your tools. 

5. Don't Keep Your Mother Plants for Too Long

Many growers attribute the transmission of HLVd to mother plants that have been used for too long. So, if you're growing a mother plant, consider testing it before each new cycle of cloning and consider changing the mother plant often. 

6. Keep Yourself Clean

Whenever entering your grow room, it is advisable to always keep yourself clean and sterilized. Wear clean clothes, wash your hands, and put on a new pair of gloves every time you enter your grow room or work on your plant. Good hygiene goes a long way when growing cannabis as it protects your cannabis plant from not only HLVd but also various other diseases like mold or mildew. 

7. Protect Your Plant from Pests

Lastly, pests may be vectors for HLVd, too, so you should also protect your cannabis plants from pests. One of the effective ways of doing that is by placing screens at every opening of your cannabis grow room. You can also consider using companion plants or other remedies to deter pests from your garden. 

Summary: How to Protect Your Cannabis from Hop Latent Viroid?

Hop latent viroid was first found in hop plants, which belong to the same family as our beloved cannabis plants. However, experts thought that HLVd was not so dangerous since it didn't show any symptoms in the crop. But over time, cannabis growers around the world started reporting symptoms that we now know as dudding, which experts found to be the result of the hop latent viroid.

Hop latent viroid has been infecting cannabis plants for some years now, but it was only discovered five years ago in cannabis plants. It has already spread to thousands of cannabis facilities across the world. And it is a notorious infection that can stunt your plant's growth and affect its quality of yield. 

So, it is best to avoid HLVd in the first place. You can do so by ensuring your cannabis plants contain good genetics, and you must also quarantine any new plants coming into your garden. Plus, you need to test your cannabis plants using HLVd testing kits regularly and keep your tools disinfected and the grow room sterile. 

If you happen to find one of your cannabis plants suffering from HLVd, you should take immediate action. For a hobby grower, the best approach is to discard the plant and cut your losses. Unfortunately, it is the only viable option until experts figure out a cure that is easy and cheap. For commercial growers, you can try alternative methods or tissue culture. The latter is expensive but also promises the best results. 

HLVd can be frustrating to deal with, but with the right knowledge, you can prevent it easily. But it is only one of the many issues that your cannabis plant may face. So, stay tuned to know more about other common issues your cannabis plant may face and how to deal with them.