Main Symptoms

Tomato spotted wilt virus (TSWV) causes zonate necrotic spots (specks) and concentric necrotic rings (ringspots) on the leaves (figures 1 and 2). Yellow at first, they quickly turn to a reddish-brown colour. The apex leaves are also distorted (figure 3).

Brown to black elongated lesions are observed on the veins, petioles and stems (figure 4). The top of the plant sometimes bends toward the ground (figure 5).

Some of the information on the worldwide distribution of the disease is obtained from surveys conducted by CORESTA (Cooperation Centre for Scientific Research Relative to Tobacco). The reliability of the information is not confirmed in all countries.

U.S. situation

Symptoms of TSWV vary with plant age, virus strain, and environmental conditions. Newly transplanted seedlings die rapidly, then swiftly decay. Plants that are a few weeks old show some characteristic foliar symptoms such as dark reddish-brown specks and leaf distortion. Ringspots, often with star-like projections into the green leaf tissue are the most characteristic foliar symptom. Older plants appear wilted because of the distortion the virus causes. Symptoms are usually most severe on one side of the plant and in the bud. Infected plants near flowering may have black streaks running down one side of the stem, often resembling burn from contact suckercides. Plants that get infected near, during, or after flowering suffer little loss. Symptoms on these plants are generally local, being restricted to the leaf or leaves that were initially infected. TSWV can be confused with diseases caused by other viruses, especially tobacco streak virus (TSV).

(Mina Mila - North Carolina State University)