Tomato spotted wilt virus

Tomato spotted wilt virus (TSWV) is a globally significant plant pathogen classified within the genus Orthotospunavirus. This virus has an exceptionally wide host range, infecting over 1000 species of both monocotyledonous and dicotyledonous plants. It is considered one of the most destructive viral diseases in agricultural and horticultural production worldwide.

The virus causes a variety of symptoms, including necrotic spotting, chlorotic rings, stem streaking, and leaf wilting. Infected crops such as tomatoes, peppers, lettuce, and ornamentals often exhibit stunted growth and reduced yields. In many cases, the fruits show irregular ripening and blotchy coloration, rendering them unmarketable and causing significant economic losses to farmers.

The biology of TSWV is intrinsically linked to its insect vectors, primarily thrips, such as the Western flower thrips (Frankliniella occidentalis). The virus is acquired by thrips during the larval stage. Once acquired, the virus replicates within the insect, and the thrips remain infective for their entire adult life. There is no transmission of the virus from parent to offspring, meaning every individual vector must acquire the virus from an infected plant.

Spread of the virus is highly dependent on environmental conditions that favor thrips populations. Warm, stable temperatures are ideal for the development of both the vector and the virus. In greenhouse environments, the virus can spread rapidly due to controlled conditions, often migrating from infected ornamental plants to vegetable crops. The high mobility of adult thrips allows the virus to travel significant distances between fields or greenhouses.

Management of TSWV requires an integrated pest management (IPM) approach because there is no direct cure for viral infections. Control tactics focus on breaking the disease cycle:

• Implementing strict weed control to remove host reservoirs of the virus.
• Using high-quality, virus-free transplants.
• Deploying sticky traps for early detection and monitoring of thrips populations.
• Application of biological controls and selective insecticides to suppress the thrips population.
• Selecting resistant or tolerant plant varieties whenever available.