Hektar

Tomato spotted wilt virus (TSWV)

Symptoms of the disease (characteristics for the diagnosis of the disease)

• The attack on the leaves begins with the young veins turning red-brown and the leaves curling downward. This is followed by the development of diffuse tan or brown spots. The wilting starts with the apical leaflets, leading to the eventual drying of the leaves.
• Bronze-colored spots and streaks appear on the stems and petioles, which later turn brown due to necrosis of the tissue.
• Fruiting is significantly reduced; green fruits may develop small black-brown spots, while ripe fruits exhibit red and yellow ring patterns. Over time, this leads to necrosis of the epidermis, causing the surface of the fruit to sink into the pericarp.

Factors favoring the occurrence and evolution of the disease, its transmission and spread :

• The tomato spotted wilt virus is not transmitted through seeds.
• This virus is spread by various species of thrips, with the most significant being Thrips tabaci and Frankliniella occidentalis. These insects can carry the virus for their entire lifespan, resulting in persistent transmission.
• The virus can survive year after year in many cultivated and wild plant species. Among the cultivated vegetables that can harbor the virus are tomatoes, peppers, eggplants, tobacco, lettuce, celery, spinach, chicory, potatoes, peas, and beans.
• Numerous wild plant species, including those from the genera Convolvulus, Urtica, Malva, Datura, Plantago, Galinsoga, Hyoscyamus, Altropa, Aquilegia, and others, can also serve as potential hosts for this virus.

Prevention and control measures :

• Conduct regular insecticide treatments to manage vector populations, primarily thrips. Preventive foliar applications should alternate among products such as Lufenuron (Match at 0.2%), Abamectin (Vertimec: 0.06–0.08% for tomatoes; 0.06–0.1% for eggplants; 0.1–0.12% for peppers), Acetamiprid (Mospilan 20 SG and Gazelle at 0.04%), and Spinosad (Laser 240 SC at 0.05%). An alternative to conventional chemical controls is the use of ecological products like Prev-Am, which contains volatile orange oil and is applied through foliar treatments at concentrations of 0.4-0.8% every 7 days. Another option is Garex B, an ecological garlic extract product that can be applied foliarly at 0.1-0.2% with 2-5 applications per season; it acts as a repellent and is biodegradable.
• Remove tomato seedlings that show signs of viral infection prior to establishing the crop in the field or greenhouse.
• Control weeds in and around the tomato crop to eliminate potential reservoirs that may harbor the virus.