Arabis mosaic virus (ArMV) in cannabis – symptoms, spread, and prevention

Arabis mosaic virus (ArMV) belongs to the family Secoviridae and is classified under the genus Nepovirus. It is a significant plant pathogen with a wide host range – including strawberries, hops, grapevines, and ornamental plants – and has also been experimentally transmitted to Cannabis sativa. For hobby growers, the virus is especially concerning because it is seed-transmissible and often latent.

Characteristics of ArMV

Virus type: Positive-sense RNA virus (bipartite genome: RNA-1 and RNA-2)
Vectors: Transmitted by soil-dwelling nematodes (primarily Xiphinema diversicaudatum)
Other routes: Transmission via pollen and seeds has been scientifically confirmed
Persistence: The virus can survive in soil for years if host plants or vectors are present

ArMV is considered a classical quarantine pathogen in agriculture and is routinely checked during seed imports – including hemp.

Symptoms in cannabis

ArMV can cause both noticeable and subtle symptoms in cannabis. These symptoms are not specific to ArMV and may overlap with those of other mosaic viruses:

Vegetative phase

Light green to yellowish mosaic patterns on young leaves
Vein-associated chlorosis
Leaf deformation: Wavy margins, slight curling, sometimes reduced leaf size
Growth disorders: Severe stunting, especially with early infections

Flowering phase

Stunted new shoots
Mosaic symptoms on leaves in the flowering region
Indirect yield loss due to reduced photosynthesis and plant vitality
No specific changes to resin or trichomes have been observed

Important: Many plants show no obvious symptoms, yet can still be infectious – especially when the infection originates from seeds.

Transmission and spread

ArMV poses challenges for hobby growers for three main reasons:

Seed transmission: Studies show that ArMV can be passed to the next generation through infected seeds – likely also in cannabis, although quantitative data is still lacking
Pollen transmission: Infected male plants can transmit the virus to healthy female plants during pollination
Soil-borne vectors: Nematodes like Xiphinema diversicaudatum live in soil and transmit the virus when feeding on roots

Mechanical horizontal transmission (e.g., through tools) is possible with ArMV but less relevant compared to viruses like HLVd or PVX.

Relevance in home cultivation

Because hobby growers rarely have access to certified, tested seeds and often use their own, the risk of silent introduction of ArMV via seed is real. Especially for outdoor growers cultivating directly in soil, the virus can also be spread by nematodes present in the substrate.

Additionally, many hobby grows lack proper diagnostics, which means ArMV often goes unnoticed and is mistaken for general “poor growth.”

Diagnostics

Reliable identification of ArMV requires laboratory methods:

RT-PCR is the most dependable method for detecting the viral RNA genome
ELISA test kits are available for ArMV, primarily designed for strawberries, grapes, or hops – they can be used for cannabis, but are not standardized for it
Rapid tests for hobby use are currently not available

Prevention and hygiene measures

Since there is no cure, prevention is the primary strategy:

Avoid untested seeds: Only use seeds from virus-free mother plants
Seed sterilization: Surface treatment with 10% bleach (1–2 minutes) or trisodium phosphate (TSP) can reduce the risk, though viruses inside the embryo may persist
Avoid soil contamination: Use new, sterile substrates whenever possible
Quarantine new plants: Grow seeds or clones in isolation and monitor them for mosaic symptoms
Nematode control (outdoor): Gardening in raised beds with sterilized soil can reduce the risk of nematode transmission

Treatment options

Currently, there is no curative treatment for ArMV-infected plants. The only way to eliminate the virus from a genotype is through:

In vitro meristem culture
Virus-free propagation from healthy tissue clones

However, both methods are technically and financially out of reach for most hobby growers. Therefore, the key strategy is: early removal of infected plants to prevent further spread.