There is an extremely damaging virus sweeping across Canadian cannabis crops and drastically affecting crop quality and yield. You may not be familiar with the virus as it is relatively new to cannabis, with the earliest known infections emerging from California in 2017. It’s called the Hops Latent Viroid, and it’s destroying LP grows all over Canada.
The virus is actually a viroid, meaning that it is even smaller than a regular virus. The viroid has historically affected hops, a genetic relative to cannabis. This is why it has been dubbed the Hops Latent Viroid. The latency aspect of the moniker comes from its ability to remain dormant in an asymptomatic plant. It was first detected in British Columbia, Canada a couple of years ago in and is said to have infected nearly 40% of Canadian licensed producer's crops.
Latency makes it very difficult to detect, requiring testing of tissue samples by lab technicians in order to verify an infection. A plant infected with the virus can pass it on to a cloned offspring, or it is spread through mechanical transmission, the use of contaminated gardening tools like shears or scalpels. HLV can lay dormant in a strain for several generations and can be transmitted by seed as well. Transmission via seed is said to be present in 8% of seeds from an infected plant.
Cold and heat treatments on tissue culture samples are effective at eliminating the virus but are costly, time consuming and unsuitable for the home grower. The most effective way to manage HLV is to eliminate the infected plants. Much like a parasite, HLV requires a host (cannabis plant) to live.
The most effective known measure to stop its spread is by using sterilized propagation equipment. A bath of 10% bleach and water solution is highly effective at eliminating the presence of HLV on gardening equipment. One should be very cautious when swapping genetics with other growers, because HLV is not easily detectable like fungus or pest damage which can be diagnosed with the naked eye.
Plants infected with HLV may become stunted, with diminished yields, brittle branching, reduced flowering, diminished THC levels and trichome production. THC and cannabinoid production in infected plants has been shown to be reduced by 50-70%! The virus will continue to degrade cannabinoid production through generations of propagating infected mother plants.
Unfortunately, to the home grower, there's really no way to be certain your plant has HLV unless you send a tissue sample to a lab. Home gardeners have referred to HLV as 'dudding disease' for years. To the home grower, they are just dud plants. The average home grower is likely to move on from the strain, and the problem is (hopefully) resolved.
For licensed producers, detection and eradication of the virus is not something to be taken lightly. The recreational market has dictated a demand for high THC cannabis, with rich terpene profiles. The Hops Latent Viroid can compromise the quality, quantity and vigor of a crop, representing unacceptable losses to an LP's bottom line. It is, however, hard to fully quantify such losses yet due to the tight-lipped nature of the industry's close-guarded secrets.
The suspected prevalence of the virus, according to the research community, highlights the importance of sourcing disease-free genetics, and developing sterilization protocols into an integrated pest management regimen. A failure to identify the disease in a commercial setting could mean losing the competitive edge in a turbulent industry.
As the industry adapts to the spread of the Hops Latent Viroid, experts say they should also take it as a warning of potential pathogenic mutations that could affect crops in the future. Cannabis grown at a commercial scale in Canada is still quite new, and we are likely to see other viruses that adapt and spread through commercial production practices.