Tospoviruses

Tospoviruses (family Tospoviridae) are a group of plant-pathogenic viruses that cause significant agricultural losses globally. These viruses are unique in their ability to infect a vast range of monocot and dicot hosts. The most prominent member of the group, Tomato spotted wilt virus (TSWV), is globally recognized as one of the most economically destructive plant viruses, impacting both protected and open-field agriculture.

The host range of Tospoviridae is exceptionally broad, encompassing hundreds of species. Major affected crops include tomato, pepper, lettuce, tobacco, and various ornamentals such as impatiens and chrysanthemum. Because these viruses can survive in perennial weeds throughout the year, they present a constant threat to newly planted crops, acting as a reservoir for local infestations.

Symptoms of infection are highly variable and often mimic physiological disorders or other pathogen-induced diseases. Common indicators include:

• Concentric chlorotic or necrotic ringspots on leaves.
• Systemic necrosis of stems and petioles.
• Stunted plant growth and terminal dieback.
• Mosaic patterns, distortion, and uneven ripening of fruits.
• Wilting that leads to the systemic collapse of the plant.

Transmission occurs exclusively through thrips, with the western flower thrips (Frankliniella occidentalis) being the most efficient vector. The virus is acquired by larvae during feeding and is maintained throughout the insect's life cycle. Consequently, once a population of thrips becomes viruliferous, they act as continuous sources of infection for every plant they feed on, leading to rapid disease outbreaks in warm conditions.

Management of Tospoviridae is challenging because there are no curative treatments for viral infections in plants. Effective control relies on integrated pest management (IPM) strategies, which include the use of virus-indexed, clean planting material and the selection of resistant cultivars. Furthermore, aggressive weed control and systematic thrips management using chemical, biological, and physical barriers, such as insect-proof netting and sticky traps, are essential to minimize viral spread in high-value cropping systems.