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Hop Latent viroid infected Chemdog.jpeg
Chemdog (same age as infected).jpeg



Visible effect of Hop Latent Viroid AKA “Dudding Disease” – same strain and age

Photos courtesy of Dark Heart Nursery

Kaprikorn's mother plants are created from donor plants that were themselves test-negative at least twice over the previous 3-4 months. New moms test negative prior to being added to the mother block.

Hop latent viroid

What is Hop Latent Viroid?
Hop latent viroid, often abbreviated as HLV or HLVd, is a highly transmissible pathogenic agent that originated in hops, and was discovered in cannabis in 2019. It is a small, circular RNA molecule responsible for causing diseases in various crops. 

How is Hop Latent Viroid Spread?

The primary method of HLV transmission is mechanical, typically through the use of contaminated tools. However, it's important to note that transmission can also occur from having sap from infected plants on clothing, hands, or gloves and subsequently touching a viroid-free plant. It is suspected that insects might play a role in the manual transmission of the viroid through their mouthparts, but further research needs to be conducted in this area to confirm this.


Additionally, there is evidence that suggested HLV can be transmitted through alternative routes, such as contaminated water sources and via seeds produced from infected plants. Viroid is prevalent in plants' roots, so it is possible that a water source shared between infected and non-infected plants could lead to transmission. 

Why Does Hop Latent Viroid Matter to Cannabis Cultivators?

HLV is alarmingly prevalent in cannabis. According to Tumi Genomics it appears to be indicative of a "cannabis pandemic."  Tumi's research has revealed that this viroid is present in approximately 75% of facilities across the United States, Canada, and Europe*. In a separate study conducted by Dark Heart Nursery, it was suggested that as much as 90% of California's cannabis facilities test positive for HLV. The detrimental impact of this viroid on yields has been estimated to account for a staggering $4 billion in lost revenue across the cannabis industry.*

In short, HLV can have severe economic and crop loss implications for cannabis cultivators. It can affect plant health, reduce yields, and compromise flower quality. Early detection and management are paramount to prevent the viroid's widespread infection within your cannabis crops.

Symptoms of HLV Infection:
You must test plants to verify they have HLV, infection cannot be confirmed visually. However, there are some symptoms that you might look out for when deciding if you want to test your plants. Common symptoms include stunted growth, leaf discoloration, decreased yield, reduced trichomes or reduced cannabinoid content. 

Kaprikorn's Prevention and Management Strategies


  • Kaprikorn has been testing mother plants for HLV since 2019. Consistent and rigorous testing is essential. 

  • Kaprikorn’s mother plants are cut from stock plants that are test-negative at the time of cutting. The new mothers are then tested again to verify they are negative for HLV before mother plants go into production and are cut on for customers.

  • New genetics are tested continuously every 3 weeks for the first 6 months to ensure they are clean, before they are cut for the first time to become mothers.

  • Every 15 weeks, Kaprikorn creates a replacement set of mother plants for every strain and the HLV testing process is repeated each time a new mother block is created. Kaprikorn's results can be viewed, here

  • Kaprikorn took part in a study with Tumi Genomics to help identify the tissue type that most reliably predicts infection. Failure to test roots can mean missing the majority of HLV infections.

  • Since late 2021, Kaprikorn has used 3 Rivers Biotech and Tumi Genomics exclusively as testing partners.  These labs have superior sample handling practices and can detect viroid at much lower levels than most other testing companies.

Sanitation and Internal Protocols

  • Between pruning or cloning on every mother plant, Kaprikorn's team uses sanitized tools. Tools are submerged in a 20% bleach solution for at least one minute--this kills the viroid. 

  • Cut on plants from youngest to oldest. Older plants are the most likely to develop infection over their lifetime. 

  • Keep mother plants on irrigation to avoid touching hundreds of plants with a single hose

Additional Resources:
For more information and support on managing HLV in the cannabis industry, you can refer to the following resources:

HLV Test Results
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