Early Pathogen Detection

With DNA-based 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.


Screen Incoming Clones

A single infected clone can spread pathogens through an entire grow. Don’t rely on visual inspections. Many pathogens remain invisible until late in the infection. Read more below.

Check Mom Before Cutting New Clones

Screen mother plants before taking any cuttings and significantly reduce the likelihood that the dozens of clones derived from that mother contain pathogens.

Protect Grow Room with Periodic Screens

Periodic screenings of grow rooms or mother plants for pathogens can help identify infected plants before they spread.

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.

Read more about Hop Latent Viroid

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.

Read more about Lettuce Chlorosis Virus

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.

Read more about Tobacco Mosaic Virus

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.


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.

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.

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.

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.

Available Pathogen Detection Products


Item # Name Reactions
420507 PathoSEEK® Cannabis Virus Multiplex Assay A Starter Bundle 200 Buy Now
420510 PathoSEEK® Cannabis Virus Multiplex Assay A 2000 Sample Bundle 2000 Buy Now
420511 PathoSEEK® Cannabis Virus Multiplex Assay A 5000 Sample Bundle 5000 Buy Now
420121 PathoSEEK® Cannabis Virus Multiplex Assay A (HLVd, LCV, and Cannabis Cryptic Virus) 200 Buy Now
420123 PathoSEEK® Virus Panel A Multiplex Positive Control 50 Buy Now
420128 PathoSEEK® Tobacco Mosaic Virus Detection Assay 200 Buy Now
420132 PathoSEEK® Tobacco Mosaic Virus Positive Control 50 Buy Now
420115 PathoSEEK® Powdery Mildew Detection Assay 200 Buy Now
420216 PathoSEEK® Powdery Mildew Positive Control 50 Buy Now
420127 PathoSEEK® Beet Curly Top Virus Detection Assay 200 Buy Now
420131 PathoSEEK® Beet Curly Top Virus Positive Control 50 Buy Now
420117 PathoSEEK® Fusarium oxysporum Detection Assay 200 Buy Now
420220 Fusarium oxysporum Positive Control 50 Buy Now
420116 PathoSEEK® Botrytis Cinerea Detection Assay 200 Buy Now
420222 Botrytis Positive Control 50 Buy Now
420146 PathoSEEK® Russet Mite Detection Assay 200 Buy Now
420224 Russet Mites Positive Control 50 Buy Now
420211 youPCR® Solution B – Powdery Mildew 50 Buy Now
420221 youPCR® Solution B – Botrytis 50 Buy Now
420223 youPCR® Solution B – Russet Mites 50 Buy Now
420219 youPCR® Solution B – Fusarium oxysporum 50 Buy Now

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

Frequently Asked Questions

Can I use youPCR® to test seeds?

No. Although we have done some initial research into using youPCR® to test seeds, we have not done enough to confidently say it works as well as testing leaf. We recommend sampling a seedling’s first set of true leaves when using youPCR®.

Can I use youPCR® to determine cannabinoid percentages?

youPCR® assays provide a positive/negative result. When using youPCR® to screen for CBDA or THCA synthase, a positive result means there is an active CBDA or THCA synthase allele. Unfortunately, that result can’t be used to predict what percentage the plant will ultimately produce. However, if you combine the CBDA and THCA tests you can determine the plant type.

  • Type I Plant (THCA-dominant) = THCA(+) CBDA(-)
  • Type II Plant (THCA:CBDA hybrid) = THCA(+) CBDA (+)
  • Type III Plant (CBDA-dominant) = THCA(-) CBDA(+)
  • Type IV Plant (CBGA-dominant) = THCA(-) CBDA(-)
Does a negative result on the youPCR® THCA Synthase Assay mean my plant will produce less than .3% THC?

No. Plants that test negative for THCA or CBDA may still produce low percentages (<2%) of either compound.

Can I use the youPCR® Gender Assay to detect hermaphrodites?

No. Cannabis plants typically hermie as a response to stress. Although there may be genetic markers that determine if a plant is more likely to hermie, we have not found them, and we do not target them with our gender test. The youPCR® Gender Assay specifically looks for a Y chromosome.

Are all the necessary consumables and equipment included in the youPCR® starter kits?

The youPCR® Starter Kits do not include PCR Thermal Cyclers. We recommend the following models:

  • miniPCR. Use Promo Code “MGC” to receive a discount off list price.

The youPCR® Starter Kits also do not include chemical reagents: Solution A, Solution B, Solution C, and Positive Control. Those must be purchased separately on the Medicinal Genomics web store.

What basic laboratory experience do I need to run youPCR® tests?

In order to successfully test with youPCR®, you should have experience with the following laboratory techniques/best practices:

  • Liquid handling with a pipette
  • Benchtop sterility techniques
  • Proper disposal of tips, punches, strip tubes
Are Medicinal Genomics products ISO certified?

All of the chemicals and reagents we sell in our webstore are manufactured in facilities that are certified to ISO 9001 and/or ISO 13485 standards.

Getting Started with youPCR is as easy as 1, 2, 3.

Purchasing Calculator