Many cannabis growers seem unaware of a common disease that is becoming increasingly common in the United States: Hop Latent Viroid (HpLVd). This story is part of a recurring series of comments from professionals associated with the cannabis industry. Joseph Ramahi, Ph.D., is the Chief Science Officer at Cultivaris Hemp, a hemp plant producer in Encinitas, California.
“Viroids are not viruses, but a plant-specific pathogenic RNA. HpLVd was first publicly announced in California in 2019 in cannabis. ” He said.
However, there is reason to believe that the California cannabis industry has been grappling with many reports of “dudding” since 2014 – stunted growth, deficiencies in trichomes, and deficiencies in secondary metabolites such as cannabinoids and terpenes. Testing for HpLVd is still not common in the marijuana or hemp industries.
An unfortunate by-product of the post-2012 wave of legalization was the spread of plants from California that were latent carriers of the viroid across the country. Although originally intended to establish legal markets across state lines, these plants unwittingly quickly introduced Viroid.
Recreational and Medical Marijuana Hygiene
Another problem that has been uncovered in recent years is the high cost of failing to follow aggressive hygiene and quarantine protocols. The lack of proper quarantine and control of new varieties as growers increase their production can open up an entire production system to infection. In the case of HpLVd, mechanical propagation through tools and gloves is the main mode of transmission. The status through which insect pests (aphids, thrips, etc.) can transmit HpLVd is still little known but is currently being investigated.
Tool hygiene is a must for any propagation, but not all disinfectants are created equal. A 10% household bleach solution seems to be the most effective way to keep viroids and viruses from spreading in your facility. Alcohol is ineffective as it doesn’t always kill viroids and viruses on tools.
While it is common in the cannabis industry to use 70% isopropanol / ethanol for tool hygiene, research in the horticultural and agricultural industries has found that bleach is the most effective and easiest way to stay clean.
Cannabis challenges ahead
The greatest challenge in controlling the latent hop viroid is the “latent” nature of the viroid. It is possible for the pathogen to invade a production system and spread quietly without showing symptoms. Many plants test positive but also show no symptoms over time, which is very problematic. It makes it difficult for growers to quantify the problems associated with viroid infection, and any harmful effects of the infection are attributed to genetics, fertility or damage from insects / sprays.
Because of the asymptomatic nature of the latent hop viroid and the fact that it is often only partially transmitted through seeds, this disease will affect both the marijuana and hemp industries for many years.
Secondary stress (heat / nutrition / pest) occurs during vegetative growth and flowering. At this point, 10 to 30% of a harvest can be lost to “dudding”. It is also possible that no secondary voltage is required. It is possible that over time, even over the years, a turning point will be reached and asymptomatic infections become symptomatic as viroid levels in the plants grow. The transmission and progression of the latent hop viroid in cannabis is currently being researched across the country.
Growing cannabis and hemp
The practice of holding the parent stock for an extended period of time and continuously reproducing from previous generation cuttings can also be problematic. Illnesses are certainly housed in poorly maintained mother’s rooms.
With the increasing spread of tissue culture in the marijuana and hemp industries, bank varieties in tissue culture laboratories and their disease testing can become the industry standard by making mother plants only with “Elite” -tested starter material and restarting mother plants from a new tissue culture material three to six times per Year.
The most important aspect of production in preparation for the 2021 season is access to pathogen-tested young plants from tested mother stocks. Along with concerns like botrytis, powdery mildew, fusarium, and other common cannabis diseases, hop latent viroid is a threat that needs testing. The idea of “clean” stock is not a new concept in horticulture. At Cultivaris, they index their maternal herd by pathogen in order to obtain an ever-growing list of diseases that affect the plants.
As testing becomes more common in the marijuana and hemp industries, questions arise about these types of tests. How often are plants tested? Which test methods should be used? Was the sampling representative of the entire system?
One problem with large mother plants is that individual parts of a large plant can test positive and negative because the viroid is not evenly distributed throughout the plant. That is, infected plants can test negative in one test and positive a few months later. Pathogen indexing is a recurring process in which multiple negative tests identify a plant as suitable for the parent herd.
Medical marijuana and recreational marijuana testing solutions
To test for latent hop viroid, breeders can use the polymerase chain reaction (PCR), a molecular biological technique that can be used to detect the presence or absence of a specific sequence of DNA or RNA in a sample. Using known sequences of viruses and viroids, it is possible to create and design PCR methods to detect them in plants.
However, the PCR methods used to identify viroids are not standardized, and some PCR methods are more sensitive than others. Cultivaris uses probe-based quantitative PCR, one of the more sensitive PCR approaches. As you prepare for the 2021 season, it is important to lay the foundation for future growth. Hygiene, hygiene, hygiene. It is an important mantra that includes tool hygiene, growth remediation, and personal hygiene.
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