Testing Infected Cannabis Plants for Hop Latent Viroid and more!

With qPCR pathogen detection assays from Medicinal Genomics, cannabis and hemp cultivators can identify plants infected with a number of molds, mites, viruses, and viroids, including powdery mildew, botrytis, russet mites, fusarium, hops latent viroid, and lettuce chlorosis virus. Cultivators who use this preventive strategy can reduce their risk of suffering costly pathogen outbreaks and improve yield.

Hop Latent Viroid

Hop latent viroid (HLVd) is a single-stranded, circular infectious RNA that completely depends on the metabolism of the host plant. As the name suggests, HLVd was first  identified in the hop plant, but it can also infect cannabis, which is a relative of hops.  In fact, some experts claim the effects of the disease are even more serious in cannabis, causing stunted plants with small, loose buds that have fewer trichomes. Once infected, plants can only be saved via a lengthy tissue culture process that will produce a new viroid-free plant.

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Fusarium is a soil-dwelling fungus that causes yellowing and wilting of cannabis leaves and stems. The fungus can sit dormant in soil for years before becoming active and infecting a viable host plant. There is no effective treatment against fusarium. Cannabis plants that are infected are a lost cause, as well as any seeds they produce.




Pythium is a soilbourne fungus that can cause crown rot or root rot in cannabis plants. In either case, the plant will wilt and die. Pythium affects a broad range of crops, including greenhouse crops, ornamentals, and field crops. As a result, the host range of the Pythium species infecting cannabis is broad and pathogens may originate from and spread to other host plants. 



Lettuce Chlorosis Virus

Lettuce chlorosis virus (LCV) is a linear, single-stranded positive-sense RNA virus and a member of the Crinivirus family. Cannabis and hemp plants that are infected early will suffer stunted growth, but may not show visual signs until a few weeks into flowering. Those visual signs of LCV infection include yellow, rolling, brittle leaves. While the infection does not kill cannabis and hemp plants, it significantly affects yield and potency. The plant will produce smaller flowers with fewer trichomes, cannabinoids, and terpenes.

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Cannabis Cryptic Virus

Cannabis cryptic virus (CCV) is a double-stranded RNA virus and a member of the Partitiviridae family. Researchers detected CCV in leaves showing signs of hemp streak virus; however, the presence of CCV alone did not cause streak symptoms. It’s possible that CCV interacts with other fungal pathogens to produce disease symptoms in cannabis and hemp plants, which is why monitoring the presence of CCV could be valuable. Furthermore, CCV can be vertically transmitted through seeds, which means breeders may want to screen plants before crossing.




Tobacco Mosaic Virus

Tobacco Mosaic Virus (TMV) is a positive-sense single-stranded RNA virus that infects a number of different plants, most notably tobacco. Although there are no documented cases of TMV infecting cannabis or hemp plants in the literature, many growers suspect TMV in plants that develop a mosaic-like pattern of discoloration on the leaves that cannot be attributed to nutrient deficiencies. Our team has screened several suspected TMV plants only to find Hop Latent Viroid. While this does not rule out the possibility of TMV infecting cannabis and hemp plants, we have not been able to confirm an infection, yet.

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Powdery Mildew

Powdery Mildew is arguable the most destructive Cannabis pest. It is an obligate biotroph that can vascularize into the plant tissue and remain invisible to a grower. It tends to emerge and sporulate 2 weeks into flowering thus destroying very mature crop with severe economic consequences. It is believed to travel in clones and its is not known if it travels in seeds. Other stressful events like cloning can trigger Powdery Mildew spore formation.

Read more about powdery mildew





Botrytis cinerea is a systemic mold infection in Cannabis. This mold is often called “Bud Rot” or “grey mold”. It can remain cryptic or dormant for long periods of time before it sporulates. The infection starts within the bud, making it difficult to detect in the early stages of infection. Peer-reviewed papers have also demonstrated that Botrytis is a systemic infection that can be passed to future generations via seeds.




Russet Mites

The microscopic Hemp Russet mite infects cannabis and can result in significant crop loss and chronic infestations. Russet mites are 200um x 45um and are thus invisible to the eye until late infection when their numbers begin to discolor the plant.

Russet mites are resistant to most pest treatments and thus care must be taken to screen incoming material to a grow. Visual detection of mature mites is possible with 14X objective loupe but eggs and nymphs likely escape convenient optical detection. They are believed to be hosts for other plant viruses.



Two Options for Pathogen Detection

Use the youPCR® Plant Screening Platform to test 4mm biopsy of the plant leaf. If the sample contains DNA of the target pathogen, a chemical reaction will turn the pink solution yellow, indicating a positive result.

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Use the PathoSEEK® Microbial Safety Testing Platform to test 4mm biopsy of the plant leaf. If the sample contants DNA of the target organism, the assay will emit a fluorophore signal that the qPCR instrument will display on a computer screen.


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Available Pathogen Detection Products

420135PathoSEEK® Hop Latent Viroid Detection Assay v2200Buy Now
420123PathoSEEK® Hop Latent Viroid Positive Control50Buy Now
420515PathoSEEK® Hop Latent Viroid Assay Starter Bundle200Buy Now
420507PathoSEEK® Cannabis Virus Multiplex Assay A Starter Bundle200Buy Now
420510PathoSEEK® Cannabis Virus Multiplex Assay A 2000 Sample Bundle2000Buy Now
420511PathoSEEK® Cannabis Virus Multiplex Assay A 5000 Sample Bundle5000Buy Now
420121PathoSEEK® Cannabis Virus Multiplex Assay A (HLVd, LCV, and Cannabis Cryptic Virus)200Buy Now
420123PathoSEEK® Virus Panel A Multiplex Positive Control50Buy Now
420128PathoSEEK® Tobacco Mosaic Virus Detection Assay200Buy Now
420132PathoSEEK® Tobacco Mosaic Virus Positive Control50Buy Now
420115PathoSEEK® Powdery Mildew Detection Assay200Buy Now
420216PathoSEEK® Powdery Mildew Positive Control50Buy Now
420127PathoSEEK® Beet Curly Top Virus Detection Assay200Buy Now
420131PathoSEEK® Beet Curly Top Virus Positive Control50Buy Now
420117PathoSEEK® Fusarium oxysporum Detection Assay200Buy Now
420220Fusarium oxysporum Positive Control50Buy Now
420116PathoSEEK® Botrytis Cinerea Detection Assay200Buy Now
420222Botrytis Positive Control50Buy Now
420146PathoSEEK® Russet Mite Detection Assay200Buy Now
420224Russet Mites Positive Control50Buy Now
420211youPCR® Solution B – Powdery Mildew50Buy Now
420221youPCR® Solution B – Botrytis50Buy Now
420223youPCR® Solution B – Russet Mites50Buy Now
420219youPCR® Solution B – Fusarium oxysporum50Buy Now

Prefer to Outsource Testing?

Cultivators who don’t have enough volume, lab experience, or start-up cash to test plants in-house can outsource to one of our partner labs. Fill out the form below and we will connect you with one in your area, if available.

Still have questions? Don’t hesitate to reach out to us.

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