The latent weed disease hop viroid attacks your plants
The so-called Hop Latent Viroid (HLV) is causing devastating damage across North America. This virus-like infection can sicken plants and destroy crops. It is highly contagious. Studies have found that perhaps 40% of cannabis flowers sold legally in Canada carry HLV. Up to 90% of cannabis in California could be infected, resulting in billions of dollars in crop losses.
What exactly is Hop Latent Viroid (HLV), how does it work and what can growers do to protect their valuable cannabis plants?
Cannabis plants can become infected with HLV when they come into contact with infected plants.
Latent hop viroid: What are viroids and how do they differ from viruses?
Viruses are tiny infectious agents. They can infect animals, plants or single-celled organisms. Much smaller than even a bacterial cell, they are made up of a small piece of genetic material (DNA or RNA) protected by a protein coat. These protective covers help preserve the virus’s genetic material and contain various proteins that allow them to infect specific host cells.
Viroids are similar to viruses, but differ in important ways. Viroids do not have a protective protein shell. Instead, they are small circular strands of RNA. They appear to have specialized in infecting flowering plants. In other words, they are tiny, “naked” pieces of genetic material that infect certain plant species and cause disease. If they infect valuable human-grown crops such as cannabis, it can have devastating economic impacts.
The “goal” of viruses and viroids is the same: replication. They cannot reproduce independently. They must come into direct contact with the right host cell, smuggle in its genetic material, and hijack the cell’s replication machinery. Eventually the host cell fills with virus particles and bursts. When you contract a viral infection like COVID or the common cold, it’s because your immune system is responding to large numbers of these viral particles circulating throughout your body.
Related
Marijuana seedlings and plant care
Latent hop viroid: What does it do to cannabis plants?
Hop Latent Viroid is a viroid that infects hop plants used to brew beer. Cannabis is a relative of hops. In recent years, HLV has transitioned from hops to cannabis. Infected plants exhibit various defects ranging from stunted growth and reduced foliage to uneven trichome coverage and reduced cannabinoid production – symptoms of what is known as “dud disease”. This is a major problem for cannabis growers whose livelihoods depend on reliably growing healthy, cannabinoid-rich plants and bountiful harvests.
Cannabis plants infected with HLV show obvious external defects: smaller overall sizes, reduced root development and discoloration. Here are some pictures. They have smaller buds (the part of the plant intended for human consumption) and can produce up to 50% fewer cannabinoids like THC.
How does hop latent viroid (HLV) spread in cannabis?
Similar to viruses, viroids like HLV must come into direct contact with their hosts in order to infect them. Cannabis plants can become infected with HLV when they come into contact with infected plants. Although HLV does not infect humans, we can spread it between plants through contact with body surfaces, tools, or equipment. Contaminated water supplies are also a major source of infection as HLV tends to concentrate in the roots.
All of these potential sources of infection allow for the rapid spread of HLV, as cannabis plants are often grown at high densities, require human contact at multiple points in the production process, and can be connected to shared water supplies (e.g., in hydroponic systems).
Latent hop viroid can also be transmitted from mother plants to offspring, both by clones produced by cuttings and by seeds. All offspring can potentially be carriers of HLV if their parent is infected. Therefore, it is important to identify infected plants even when there are no obvious external signs of infection or when you are working with tissue culture systems with physically isolated samples.
Because HLV is so contagious, it has already spread widely and caused massive losses to cannabis growers. It is likely to spread further. Farmers must be prepared.
How can farmers protect themselves from latent hop viroid (HLV)?
Whether farmers are already fighting HLV or not, they must have procedures in place to test for and remove infected crops. Learning how to visually identify potentially infected plants is obviously important, but it’s always possible to miss subtle signs.
As far as I can tell, the only reliable way to be sure if plants are infected is to do genetic testing, much like one would do to detect something like COVID infection in oneself. A sample must be taken from a potentially infected person and subjected to a laboratory test that can detect the presence of genetic material from a specific pathogen.
For cannabis growers, this means either building their own capacity and buying test kits, or sending samples elsewhere for testing. Any plants known or suspected to be infected with HLV must be removed immediately to prevent spread of infection. Plants in close proximity should be quarantined or closely monitored even if they show no signs of infection.
Diligent action could mean the difference between a few infected plants and the loss of an entire crop.
The research team of Dr. Zamir Punja has conducted studies to examine how well HLV infections can be treated using a test-and-remove approach. They were able to reduce the proportion of infected plants from 35% to 7% over a seven-month period. In other words, managing an HLV outbreak is likely to be time-, labor-, and cost-intensive. It is advisable for commercial cannabis growers to have a robust detection process in place before individual infections become full outbreaks. Diligent action could mean the difference between a few infected plants and the loss of an entire crop.
Other preventive measures should also be taken. HLV is surprisingly stable on surfaces and can survive on equipment or plant material for days or even weeks. This viroid is also apparently able to withstand high heat, UV radiation and disinfectants to some extent. For these reasons, farmers need to be proactive and conscientious about hygiene. Are tools and equipment completely sterilized between uses? Do supplies and staff travel between rooms with different plants? How often are disposable items reused and thrown away?
Related
Identifying bud rot, mold and root rot on marijuana plants
All large-scale growers with dense crops should be prepared, especially if their plants have a shared water supply, nutrient sources and soil. Given the rapid spread of HLV, cannabis growers everywhere should be prepared. As we all probably know by now, viral outbreaks are difficult to manage and can be extremely disruptive. Growing cannabis is difficult. It is a science and an art form. In an already competitive market with slim margins and the inability to deduct normal business expenses due to marijuana’s Schedule I legal status, every harvest counts.
Be prepared.
Post a comment: