HLVd: The Menace to Cannabis Crops

Sweeping and dismantling numerous cannabis crops throughout the cultivation space, you need to look no further than at the plant disease called hop latent virus (HLVd). Also known as Dudding Disease, the virus needs in order to survive and reproduce, a compatible host which it has done in several other plant species but has now made its entrance into cannabis cultivation.

In continuation of our cultivation education series, Adam Jacques, a world-renowned expert with more than 20 years’ experience cultivating various unique strains of cannabis, as well as the Chief Geneticist at AgSense LLC, and Zacariah L. Hildenbrand, a research Professor at the University of Texas at El Paso, the principal founder of Inform Environmental, a partner of Medusa Analytical, and is a director of the Curtis Mathes Corporation, get to the root of the issue of experiencing an HLVd infestation and if anything can be done to salvage your crops.

Can you tell us about the Hop Latent Viroid (HLVd) virus and how have you seen it affect cannabis crops?

Adam Jacques, Chief Geneticist at AgSense LLC | Image Credit: © Adam Jacques.

Adam Jacques: These kinds of viruses started, we started noticing with this probably 15 years ago, right? And it got called everything tomato mosaic, hemp mosaic, you know, all of these, and everybody was considering it. Well, this must be a mosaic virus of some sort of tobacco mosaic, maybe. What we started seeing was what we call Dudding, the production of plant material wasn't great. You would see lower numbers, reduced yield, and would get worse over time. And so, you know, everybody was trying to come up with, 'well, what is this?' Obviously, now, we know it's HLVd, right? So once that got figured out, really, it was just, at that point, figuring out what are the metrics of damage that it's doing to the crops? It's not like hemp mosaic virus isn't a thing. It's a thing that exists and it expresses itself roughly in the same way. So, when we start talking about hop latent virus, we do to really know what you have, you're gonna need a lab test on it. I would say that, as of right now, I would be surprised if any number less than 50% of clones—and it's in this country—didn't have it.

Zacariah Hildenbrand, PhD, research Professor at the University of Texas at El Paso, the principal founder of Inform Environmental, a partner of Medusa Analytical, and a director of the Curtis Mathes Corporation | Image Credit: © Zacariah Hildenbrand.

Zacariah Hildenbrand: It's ubiquitous. From what I see, right, with so much of this poly hybrid desertion, with all these genetics, just being mixed and mingled together, there really hasn't been much concern for 'Are there any, is there any kind of genetic baggage associated with doing this', right? It's just like, 'Hey, this genetic was fire and this other genetic is fire, and I'm gonna put fire and fire together and it's gonna be 10 times better' and there's just no consideration for the genetic lineage and, and you can be stuck with hop latent viroid. The issue with this too, is you can have plants that appear asymptomatic for quite some time, and yet they're still carrying the virus. They're almost like a vector, if you will, and then boom, you then introduce that with another genetic. Based on the genetic background, maybe then the virus expresses into its actual phenotype and condition. And then you got a real problem. I think the folks at Medicinal Genomics probably have the best handle on this. They published a bunch of papers on this looking at hop latent viroid's prevalence across various genetics. And I mean, to Adam's point, it's well over 50%. I mean, it's everywhere. I think one of the questions I asked him is if you could detect this in the seeds? Or if or how long do you have to wait until this starts being detectable in the plant? And they were still working on that. But it's a ubiquitous issue with varying effects on client's outcome, and it still remains to be determined how to completely eradicate it.

How does HLVd avoid detection?

Jacques: A lot of ways to do this in this industry is observational. It's not like I'm going to every plant and doing a test on it every day to see if it has a virus or an issue. A lot of the things that I'm doing is with my eyeballs. So, if I have spider mites or russet mites, or something like that, I can visualize it. This is, it hides in the plant itself. So, it's not really expressing a lot of things that would cause me concern, especially in the vegetative state. I mean, you do things like stunted growth, reduced vigor, brittle stems, you know, less flower mass, those things happen. But in a newly planted clone and fresh soil who's real healthy, it may be using that energy fighting that virus, but it's in such a healthy state at this point that you're not really seeing any of the side effects. So, when you flip it into flower, and you start going and you're adding stress to the plant into a flowering cycle, and trying to push weights and things like that, that's when you really see the energy of the plant, focusing from production of the plant into fighting the virus in the plant. That's where you really start to see a lot of the side effects coming out at that point. It's too late, right? You've already wasted six weeks. Everything is stunted. Another awesome thing about this disease is that let's say you grow in aeroponics. Well then, your entire water supply and all of your lines are infected now because it will transfer through the roots. So, it hides by not being a big problem until it is.

Hildenbrand: It's a really good virus. Good viruses are one that really don't perturb their hosts much and their whole goal is just to spread its DNA. A really bad virus is one that's lethal, kills its host before it can spread on, but this one's actually quite effective in that it spreads so readily without having a significant impact on the host until it does. I've always seen it with the virus, that it's a really steep decline. It's like, 'Oh, there's something weird going on with this plant' and Adam's, right. You may see it initially in the veg, like, 'Ah, maybe it'll be okay here'. And then all of a sudden, it's just like, 'Wow, this looks terrible. We don't have any trichrome production, we have weird leaf morphology. Now we have discoloration, this plant is dead'. So, or it might as well be dead. You just end up sacking it anyways. So, it's definitely one of those things that if you're not on top of it, can be a major issue. And a lot of people to, kind of going back to my comment about the polyhybridism, people are so eager to get genetics from other folks. We've discussed about, you know, the prevalence of mites and bugs and pathogens, and but what about the prevalence of viruses that you're passing back and forth? You know, I think people need to be more cognizant of the provenance of the genetics that they're getting, before they get super excited about the new hype strain out of someone's garage.

Why should cultivators and consumers be concerned of HLVd?

Jacques: Consumers don't need to be. It's an issue with the cultivators. It is bad for the cultivators, you're looking at a 10 to 15% loss in cannabinoids, you're looking at a 30% loss and weight off of the plants. You're looking at a much lower quality flower. So, something that may have been top shelf money, you're now getting B or C grade money for less and you're getting less and the THC percentage sucks. Stuff duds out. It's just terrible. It's gross, right? So, it turns good flower into [unusable] flower. On the consumer side, you know, I don't think we'll ever see a financial hit to them on it being that the industry is what it is right now. I don't think smoking something that had hop latent viroid is going to do anything to you. But, if you are getting cannabis from like let's say your grower or your caregiver or something that it is this, you're getting a much lower quality product than you should be getting. So, I guess you're damaged a bit in that way.

Hildenbrand: Yeah, I don't think the virus can transform from plant kingdom to eukaryotic animals. I don't think that's the thing. But to Adam's point, it's just it's going to result in a diminished product, it's going to be less efficacious. And so obviously is not going to be the same medicinal value, as if you had an uncontaminated sample.

Jacques: And as a grower, those things that I mentioned, that is your margin, right? You'll go bankrupt if you have it and don't deal with it.

What can be done to prevent or contain the effects?

Jacques: So before I bring anything into my room, I would prefer to get a test on getting hop latent tests and getting tests isn't difficult, like I have to go to the university now to get something like that. You can actually buy testing kits online to test your plants for hop latent. Before you bring anything into your room, or if you're starting from seed or something new like that, it probably would behoove you to test for viruses in your plants. If they do have viruses in your plants, it's not a death sentence for the plant necessarily, right? We can fix this. But it's tough. Honestly, it's tough not to bring this into your space right now.

Hildenbrand: Yeah, it's just so ubiquitous. So, I think really, it just goes back to having a strong understanding of the reliability of the source of your genetics. I think that's your best course of action, getting it from people that take care of their plants, sterilize things that they can, and just run a clean operation. I think the worst mistake you can make is just haphazardly taking a clone from some bro that you met, and you just have no idea what sort of conditions they were dealing with there and then boom, you could have systemic termination of your entire facility.

Are there any other cannabis pathogens to be worried about? (Fusarium, Pythium, etc.)?

Jacques: Mosaic viruses, I would keep an eye on, they can do damage and the damage looks a lot like this. So, it's roughly the same. That's the one everybody was looking out for. For a long time. Specifically, tobacco, hemp, and tomato mosaic viruses. As far as viruses go, that's about, you know, those are the worries that that I have.

Hildenbrand: And then just the fungi, you know, Botrytis, those sorts of things. Aspergillus.

Jacques: Aspergillus, even powdery mildews. That's tough because that's systemic? Aspergillus will kill you so it’s a good one to worry about.

Is there any products you use/recommend to detect or use to deal with an HLVd infestation?

Hildenbrand: Yeah, I would just say again, it just goes back to the analytical techniques, [polymerase chain reaction] PCR. I think it's becoming so readily available, that you could have kind of at home kind of garage enthusiast, if you will, running their own PCR as a supplement to their grow. And it's been nice. I mean, we've seen the entire industry, like the folks at Shimadzu or the folks at Agilent. They're trying to take their cannabinoid analysis and their terpene analysis and make it kind of miniaturized so that the at-home user, maybe it's more accessible, and that the instruments are becoming cheaper. I think in five years' time, if you're a commercial outfit, you're going to have your own [high-performance liquid chromatography] HPLC to do cannabinoids, you'll have your own [gas chromatography mass spectrometry] GC-MS, to do terpenes, and you'll have your own PCR to do virus testing. And that's just going to be part of your daily protocol.

Jacques: I would say as far as products go to deal with this, no. There's not something you can water in or spray on the plant that's going to save it. If you have a virus in real life, same idea, right? You need to find something that's a directed cure for that thing, which just doesn't exist yet for this. You can make your plants healthier, which is going to help mitigate the damage that this virus is doing. But then you're just putting cost on top of costs to try and keep a sick plant alive. But no, there's no answer to fixing it in a product or a bottle that you can buy.

If you know somebody who's really good at tissue culture, you could go in and do a sanitizing tissue culture on it and that has been proven to remove the virus from plants. So, if there's a plant that you really want to keep in your stable, you can put out the financial needs to get something tissue cultured and completely cleansed like that. It does work, I’ve seen it. It's a lot to do for, let's say, 500 plants in a grow. Let's say it's some killer genetic that's unique to you, and you want to keep it and it has an illness, there are ways to remedy this. But the plant doesn't like it. Plants don't like getting bleached necessarily. And I would, there's certain genetics that if that issue came up with them, I would find a way to save them. I would go that far to save those genetics. But I would say, for the average home grower at home, if all of a sudden you figure out that's what's happening, just rip it out and start again. Getting your plant tissue cultured and cleaned, like that's going to cost more than grow in that plant’s worth.

Hildenbrand: If anyone experiences this for the first time, just start over. Don't try to play Sherlock Holmes to figure out where it came from and how to solve it. Just start over with new stuff and hopefully go back to the basics.

What are the risks of clone sharing?

Jacques: I think clone sharing in general is as old as growing this plant is. It's like baseball cards amongst each other. Right? Who's got the new, unique elite thing? When me and Christian West started out, that was the thing, right? You would go and you go around, you collect all the clones from the different areas and that's how you got genetics. Now, I don't think my number 50% + is wrong of clones out there, have this. Generally, you're not going to see this expressing itself in a clone. So, you have no way of knowing with clone sharing whether you're getting a clean clone or not. Could there be systems put into place to make that easier, like maybe a certificate of testing on it or something, but then all of a sudden that clone’s cost is not $20 anymore. It's hundreds of dollars to get a clean clone. I can't fault people for sharing clone and seed. That's a tough thing to do and it's exciting thing to do. And then you get new things. Turns out that can come with a lot of issues.

About the Guest Columnist

Madeline Colli is the Editor for Cannabis Science and Technology magazine. Direct correspondence to: MColli@mjhlifesciences.com.

How to Cite This Article

Colli, M. HLVd: The Menace to Cannabis Crops, Cannabis Science and Technology, 2024, 7(3), 14-17.