Beet curly top virus (BCTV) in Cannabis – Symptoms, Leafhopper Transmission, and Protection Strategies

Beet curly top virus (BCTV) is a major plant virus that can cause devastating damage in outdoor cannabis cultivation. It belongs to the Geminiviridae family (genus Curtovirus) and is notorious for its leaf-curling effects. In North America, infection rates of over 80% have been reported in hemp fields. A critical point: the virus is spread by leafhoppers (Circulifer tenellus) — and not via seeds or cuttings.

General Information

Name: Beet curly top virus (BCTV)
Taxonomy: Family Geminiviridae, Genus Curtovirus
Genome: Circular single-stranded DNA (ssDNA)
Host Plants: Very broad – over 300 species including cannabis, beet, tomato, and spinach

Transmission

Main Vector:

Beet leafhopper (Circulifer tenellus)
→ persistent circulative transmission (the virus circulates and replicates within the insect)

Notable Points:

Not transmitted via:
- Seeds
- Pollen
- Cuttings
- Tools or mechanical means
Cannabis is only infected by viruliferous leafhoppers in outdoor settings.

Symptoms in Cannabis

Vegetative Phase:

Distinct mosaic patterns with light and dark green patches
Severely curled or twisted leaves (“Curly Top”)
Stunted growth, dwarfism
Thickened, leathery leaf texture
Upward-curling leaf edges

Flowering Phase:

Mosaic and curling symptoms continue on upper plant parts
Flowers may be smaller or completely absent
Plants may die prematurely
Buds are deformed, underdeveloped, and of low quality

Diagnosis

Visual Inspection:

Combination of strong leaf curl and mosaic pattern is typical of BCTV
Can be confused with CMV or PVY — but CMV rarely causes such strong curling

Lab Testing:

PCR-based detection of the viral ssDNA is reliable
No immunostrip (rapid test) currently available for BCTV in cannabis
Some labs offer BCTV tests on request

Relevance for Home Growers

Between 2019 and 2021, BCTV caused significant damage in commercial hemp fields across the USA. Outdoor grows are particularly at risk, especially if located near beet, tomato, or spinach fields — common habitats of the beet leafhopper. For indoor cultivation, BCTV is virtually irrelevant, as the vector cannot enter controlled environments.

Prevention and Management

Key Measures:

Controlling leafhoppers is essential
Use fine mesh insect netting in outdoor settings
Yellow sticky traps for monitoring (though less effective for leafhoppers)
Weed removal around the grow area (many weeds act as hosts)

Additional Strategies:

Avoid planting near high-risk crops (beet, tomato)
No special requirements for cuttings/seeds, as no vertical transmission
Remove infected plants when infection is suspected

Treatment Options

There is no cure for BCTV-infected plants. Thermal or chemical treatments are ineffective against DNA viruses like BCTV. A single viruliferous leafhopper can infect an entire crop — therefore, preventive protection against leafhoppers is the only effective strategy.