How to Test for Hop Latent Viroid in Your Cannabis Cultivation Facility, and What to Do If You're Positive

Cannabis cultivators have always faced a long list of enemies in the garden. Cultivators work tirelessly to ensure their facilities are free from harmful cannabis plant pests and pathogens. Some are easily seen and controlled with proper cannabis cultivation hygiene, while others are more discreet as they proliferate. 

The newest threat to hit growers is a cannabis plant disease that can drastically affect plant vigor and yields: the Hop Latent Viroid (also known as HLV, HpLV, HpLVd, HLVd, or “dudding” disease), a microscopic agent that can wreak havoc on your crops—if it isn’t already.

Hop latent viroid has become a hot topic of conversation for cultivators across America for good reason. HLV, first reported in California in 2019, is one of the most significant threats to face the cannabis industry—on the garden side, anyways. In this guide, we will explore what HLV does to cannabis and the steps you can take to test for it in your cultivation facility. Additionally, we will delve into best practices for dealing with a positive result, focusing on the importance of cannabis cultivation protocols to minimize the risk of further contamination.

HLV Symptoms in Cannabis

Hop latent viroid (HLV) is a pathogenic RNA molecule that affects plants, including cannabis (and its botanical cousin hops). It belongs to the family of viroids, which are small, single-stranded RNA molecules that lack a protein coat. HLV is particularly concerning because it can remain latent in plants, meaning it may not show visible symptoms while still causing harm. When symptoms do appear, they can include stunted growth, reduced yield, leaf curling, and other abnormalities. 

These symptoms, and the effect of the viroid on the health of the plant, can be very strain-specific, with some strains showing signs of reduced vigor in growth, root development, yield and quality, while other strains can show no signs at all, only serving as a discrete host for the viroid, ready to transmit to its susceptible neighbor through a cultivation tech’s unsterilized set of pruning shears. HLV can easily spread through infected plant material, tools, soil and even nutrient runoff.

How Does HLV Hurt Cannabis Cultivation Facilities?

HLV has become a significant concern within the cannabis cultivation community due to its ability to damage plants without immediate signs of infection. Its widespread presence is attributed to the global movement of plant material, making the spread of HLV in the cannabis industry nearly inevitable. The viroid can devastate cannabis gardens by diminishing yield and overall plant health, leading to economic losses for cultivators. 

California has been hit particularly hard over the last few years, with online clone nurseries and dispensary clone racks serving as major sources of cannabis disease transmission. 

Truly no commercial cannabis cultivator that uses clones is immune. By the time cultivators understood the risk of HLV, it was too late: Clones had been purchased from unsanitary dispensary clone shelves or ordered online from infected nurseries and brought into the gardens of the most popular brands and the largest multi-state operators. Garden staff went about their day-to-day, and in facilities that lacked proper cultivation hygiene protocols, they were spreading the viroid to everything they touched.

HLV may be prevalent in some of the oldest cannabis markets in the U.S., but it presents an added challenge for growers in emerging markets. If a business sources diseased cannabis clones during the immaculate conception—that brief period of time when state regulators typically look the other way while cultivators acquire plants in newly legal states—that business will struggle to course correct after the window has closed. Not only does HLV blow clone and seed budgets, it can be hard to find new plants from a reputable source once regulators start enforcing seed-to-sale tracking.

Testing for Hop Latent Viroid in Cannabis Plants: Best Practices

Testing for HLV is a crucial step in preventing its spread and managing its impact on your cannabis garden. While the science and our understanding of how the hop latent viroid moves through the plant, along with the most accurate and effective way to test for it, continues to evolve, we’ve put together a guide to testing for HLV in your garden based on what we know today.

How to Select and Collect HLV Sample Materials

Choose plant material that is representative of the plants in your facility. Consider root sampling, as the hop latent viroid can be present in the roots even when it's not evident in the foliage. Wear new, disposable gloves and use sterilized tools to collect samples. Make sure not to touch non-sterilized surfaces or other plants during the process to prevent cross-contamination.

Best Hygiene and Sanitary Practices to Stop Hop Latent Viroid

Clean all tools and surfaces before and after sample collection. Sanitization helps prevent the accidental spread of HLV between plants. Tumi Labs, the Colorado (and possibly U.S.) leader in HLV testing and research, recommends sterilizing tools like pruning shears and gloves in a 10% bleach solution for at least 30 seconds between plants—that’s a lot longer than you’d think!  Next Big Crop uses Tumi Labs for all of our testing needs.

Hop Latent Viroid Sample Storage and Delivery

Place samples in airtight containers and keep them cool during transportation. If possible, deliver the samples to the testing lab on the same day they were collected to ensure accurate results. Use laboratory-provided test sample containers and packaging, if available. Be sure to label all samples (and the source plants) accurately. Create a spreadsheet that includes the sample number, strain name and source plant for simple tracking once results are received.

My Garden Has HLV, Now What?

Discovering HLV in your cannabis garden requires swift and thorough action to prevent further spread. Your cannabis growing SOPs need to be clearly communicated with the facility team, and followed to the letter. It starts with isolating the problem areas and protecting non-infected plant stock with cultivation hygiene protocols. Follow these steps:

1. Remove Contaminated Plant Stock. Identify and remove infected plants immediately to prevent the viroid from spreading to healthy plants. This requires some tough decisions— cultivators can get super attached to their favorite strains and the idea of killing off a great genetic can be heart-breaking, but unless you plan to remediate the strain through tissue culture (see below), it’s best to take the advice offered time and time again in numerous zombie movies: The infected ones gotta go.

2. Isolate Plants in Question. Isolate plants that are suspected of being infected to prevent potential contamination of healthy plants. Verify test results and even retest to ensure you are keeping only uncontaminated cultivars/plants.

3. Use Separate Tools. Designate tools and protective gear such as gloves and overalls exclusively for quarantined areas to prevent cross-contamination. Clean tools thoroughly with a 10% bleach solution for at least 30 seconds between each plant.

4. Have Hygiene Protocols in Place, Facility-Wide. Regularly sterilize all tools and equipment, even if they haven't been in direct contact with infected plants. This practice helps maintain a clean environment and minimizes the risk of infection.

5. Remediation Techniques. If valuable or essential strains are infected, explore remediation techniques. Modern tissue culture methods can isolate clean plant cells from the viroid, offering a chance to salvage crucial cannabis genetics.

6. Consult Genetic Experts. Work with qualified genetic consultants who specialize in HLV testing, elimination, and remediation. They can guide you through the process of sourcing cannabis genetics that aren’t contaminated and the implementation of effective processes to ensure the hop latent viroid is managed properly.

Maintaining a healthy cultivation facility and cannabis strain library requires diligence and a commitment to effective testing and mitigation strategies. Hop latent viroid poses a significant threat for all cannabis cultivators, but with proper testing, cannabis growing SOPs, and timely action, you can minimize its impact and ensure the success of your cannabis garden. Remember, prevention and proactive measures are key to safeguarding your investment and maintaining a thriving cultivation operation.

We grow, so we know: The team at Next Big Crop is deeply experienced in creating cannabis cultivation SOPs that improve facility efficiency and safety for the long term. Reach out to learn more