Tomato Spotted Wilt Virus (TSWV) in Cannabis – Symptoms, Thrips as Vector, and Protective Measures

Tomato spotted wilt virus (TSWV) is a major plant pathogen in the genus Orthotospovirus, known for causing significant economic damage in ornamental, vegetable, and crop plants worldwide. Cannabis can also become infected with TSWV—especially in enclosed cultivation environments like grow tents or greenhouses when infected thrips are introduced.

General Information

Name: Tomato spotted wilt virus (TSWV)
Family: Tospoviridae / Orthotospovirus
Genome: Segmented, negative-sense single-stranded RNA
First described: 1919
Distribution: Detected in over 1,000 plant species worldwide

Transmission Pathways

Vector: Thrips, especially Frankliniella occidentalis
Mode: Persistent-propagative – the virus is acquired by larvae, replicates within the insect, and is transmitted throughout the adult thrips’ life
No transmission via seeds, cuttings, or tools

TSWV is entirely vector-dependent. Without a suitable thrips species as a carrier, the virus cannot spread.

Symptoms in Cannabis

Vegetative Phase:

Irregular pale (chlorotic) spots
Bronze to necrotic lesions along leaf veins
Possible leaf curling or deformation
Stunted growth, reduced leaf size

Flowering Phase:

Wilting of young shoots or flower clusters
Reduced trichome and bud formation
In severe cases: dieback of entire shoots

Since symptoms are often mistaken for heat damage or nutrient deficiencies, laboratory confirmation is recommended.

Diagnostics

Rapid Test: TSWV ImmunoStrips (e.g., by Agdia or Loewe Biochemica)
Lab Analysis: RT-PCR or ELISA tests from specialized plant pathology labs

Rapid tests are relatively accessible to hobby growers and deliver results in about 10 minutes.

Prevention and Control

Vector Control Is Crucial:

Use blue sticky traps to monitor thrips
Install insect mesh on air inlets
Apply biological controls: predatory mites (Amblyseius swirskii) or green lacewing larvae
Avoid co-growing with ornamentals (e.g., gerberas, dahlias) that may serve as virus reservoirs

Hygiene Measures:

Quarantine new plants for at least two weeks
Remove and destroy infected plants completely
Clean tools, even though no mechanical transmission is known

Importance for Home Growers

Although TSWV is still rare in cannabis, it can be introduced via infected companion plants or nearby crops. Indoor grows with decorative or vegetable plants are particularly at risk. There is no treatment for infected plants, so early detection and vector management are the best strategies.