Growers have long speculated the reason for “duds” seen across clonal varieties of cannabis.

A first discovery of Hop Latent Viroid (HLVd) in cannabis has finally offered some answers to this costly and confounding problem. Thankfully, HLVd is primarily spread through mechanical transmission, meaning it can be easily controlled when using best practices for cleanliness in your grow rooms.

Phylos’ discovery of the Hop Latent Viroid (HLVd) in cannabis took place in partnership with Glass House Farms in Santa Barbara, CA. You can learn more about our discovery and scientific methods in the August 2019 edition of Plant Disease, the leading international journal on new, emerging, and established plant diseases. Since discovering HLVd and completing our own additional testing, a second discovery was confirmed


Glass House Farms Discovers a Problem

Just outside Santa Barbara, California, Graham Farrar noticed something strange happening in his production rooms — a number of plants were lacking oil, heads were small, leaves were misshapen and yellowish in color and branches were brittle. 

Farrar, owner of Glass House Farms, is a self-proclaimed “tech geek” with a background as a developer for companies like SONOS. His rigorous approach to cultivation left him baffled as to the cause of his sick plants. “We’re in a homogenous environment with automated controls, so it’s unusual to see plants scattered throughout exhibiting symptoms of sickness.”

His curiosity led him to do investigative work through universities, including UC Davis. Eventually he was connected to Jes Staha, Chief Technology Officer at Phylos. After experimentation on the “dud” plants, the cause was finally discovered — Hop Latent Viroid (HLVd). 

How You Can Control the Spread of HLVd in Your Grow Rooms

The viroid is spread through mechanical transmission with non-sterile pruning tools and scalpels as the most common culprits. Transmission typically happens when infected tools come into contact with wounds in the plant. It has shown to be non-transmissible by aphids in hops. While seed production does not appear to be the primary mechanism for transmission, some researchers have shown that HLVd can be transmitted via seed at an approximately 8% rate.

Using well established biosecurity management such as not using clippers on an infected plant can reduce or stop transmission. The best way to control the spread of HLVd is to get rid of infected plants as soon as HLVd is detected. If this is not an option (because you want to save the stock plant, for example) viruses and viroids can generally be eliminated through heat and cold treatments of meristem via tissue culture.

More About the Phylos Detection Method

We isolated RNA from perceived sick and healthy plants in the same Southern California facility in February 2018. We then sequenced the samples and compared them to one another. We were specifically searching for non-cannabis sequence fragments that were only present in the sick plants and not the healthy plants. Check out detailed experimental methods and protocols in our publication


Shout-outs: This project was a cross team collaboration. It is only by combining in-field experience with sequencing in the laboratory and then data analysis that we were able to shed light on this elusive issue. Kristen Waterman and Kayla Hardwick, PhD were essential members of the Phylos team.