What is wrong with my Cannabis?

Over the last couple of years, the cannabis industry on the west coast has increasingly been dealing with a ‘mystery’ issue. At first, many referred to it as “dudding”. Cannabis plants were not performing to expectations. Smell, taste, potency were all affected — even in strains that had just completed a solid run. 

Everything was smooth sailing until you went into flower. Then, a general lack of vigor started to show: brittle branches; lack of trichome production; a yellowish tinge to the buds; odd-canopy formation; the list of symptoms goes on. What gives?

The epidemic spread rapidly in California, with people really taking note in 2019. But now, as we enter Oregon and Washington’s 2021 harvest season, this ‘unknown’ disease may be affecting more farms than we know in Oregon, Washington and beyond.

What is Hop Latent Viroid (HLVd)?

Hop latent viroid (HLVd) is an infectious, RNA pathogen that is completely dependent on its host plant’s metabolism for replication. As the name suggests, HLVd occurs worldwide in hops, but has also been found to affect cannabis.

How does Hop Latent Viroid affect Cannabis and Hemp Plants?

If HLVd is the only pathogen present, it will not likely kill the plant or even cause obvious symptoms of infection before flowering (i.e., curling or yellowing leaves). However plants will show subtle symptoms and be more susceptible to other infections/pathogens.

HLVd can greatly reduce the quality and quantity of the flower the infected plant produces.  During the vegetative stage, plants may grow shorter with smaller leaves and tighter node spacing. Flowering plants may have smaller, looser buds with much fewer trichomes. At Pinnacle Analytics Lab, we have found that plants infected with HLVd may have <50% of the cannabinoid content of healthy plants — sometimes as low as 6%.

How can Hop Latent Viroid be Controlled?

Although HLVd can be eliminated from a cannabis or hemp plant via tissue culture, it is a long and laborious process that should only be reserved for cultivars that are critical to your business.

With HLVd, prevention is key. Creating and upholding adequate sanitation procedures will significantly contribute to preventing the spread of HLVd and all other plant pathogens. It is recommended to use fresh gloves and sterile tools each time you handle a plant. If gloves are going to be reused, be sure to sanitize them before touching another plant.

If possible, cultivators should screen their mother plants, via qPCR, before taking cuttings to ensure they will be free of HLVd. It is also recommended that incoming clones be screened to verify infected plants will not be introduced to your grow.

List of Potential Symptoms

Note: These are not necessarily indicators of HLVd but come from feedback we are constantly gathering via clients and other sources.

• • Lack of vigor
  • Smaller leaves
  • Weak branch joints (even in younger stages)
  • Branches out more like a broomstick (widely spread branches that ‘SCROG’ themselves flat) unlike a more naturally ‘rounded’ plant with identifiable main cola(s).
  • Small, ‘popcorn’ nugs
  • Close internodal spacing
  • “Yellow head” – Lack of trichome production leads to a yellow tinge on cola tips
  • Alfalfa or hay smell – Lack of terpene production

Grow Facility SOP Tips for Sterilization

• • Use a 10% bleach/distilled water solution for sterilization. 70% ethyl alcohol has also been proven successful, but bleach is recommended. Mechanical transmission is the main spreader.
  • WIPE tools clean, not just a dip. Keep sponges and buckets of solution on hand whenever using tools. ISOPROPYL ALCOHOL IS NOT AS EFFECTIVE.
  • Use a new pair of scissors, or razor blades, when taking cuttings from mom stock and when pruning if possible.
  • Quarantine potentially infected plants. Unfortunately, there is not yet reliable information on the amount of time it takes for a plant to become systemically infected or if insect transmission is possible.
  • Until more research becomes available, it is better to be safe by isolating potential problems!

Further HLVd Education

Future Cannabis Project YouTube Video — Interview with Glass House Farms and Dark Heart Nursery. (Great discussion by growers and scientist from UC Davis who helped discover HLVd in California

Encore Labs Article — A Novel RNA Virus (quick descriptive article; importance of screening in commercial agriculture)

APS Publication: Occurrence of Hop Latent Viroid in Cannabis sativa with Symptoms of Cannabis Stunting Disease in California — Study completed by Phylos Bioscience sequencing plants and confirming RNA virus

Darkheart Nursery Article: What is Hop Latent Viroid? — The nursery in California who investigated the issue and helped discover that HPLV was the source of the problem