Tomato spotted wilt affects tomatoes, and numerous other vegetables, ornamentals, field crops and weeds. The disease can cause significant yield losses of tomato.
TSWV is vectored by at least eight species of thrips, which acquires the virus during the larval stage, and transmits the virus during the adult stage.
Tomato spotted wilt can cause severe severe stunting of the plants very early after transplanting into the field. It is typically an issue in spring in N. Florida, but symptoms can also be seen in fall.
A characteristic symptom of plants affected by tomato spotted wilt is leaf spots which form concentric patterns. These patterns can be present through the entire section of the leaf.
Leaf spots may resemble that of bacterial spot. Leaf spots associated with tomato spotted wilt have a unique blotched lesion appearance compared to bacterial spot that tends to break in the center.
Leaf spots can entirely cover whole leaves and many leaves throughout the plant. At this stage the symptom is pronounced and very characteristic of tomato spotted wilt.
Another characteristic is netting pattern on leaves, and in some cases many leaves. This is not a common symptom but can be seen from time to time.
Leaf purpling and leaf upward curling is another symptom of plants affected with tomato spotted wilt. However, other diseases can also cause similar symptoms.
It is common to see plants affected with tomato spotted wilt having high number of adventitious root formation. Other diseases and abiotic stress can also cause similar symptoms.
While not always seen in plants affected by tomato spotted wilt, plants with severe wilting may have symptoms of severe necrosis and collapse of the pith.
Tomato spotted wilt causes major direct effect on fruit appearance and quality. Early stage fruit symptoms including mild circular or oval pattern development on green fruits.
Numerous small ring spots on a fruit from a plant affected by tomato spotted wilt. Ring spot symptoms can vary with different tomato cultivars and stage of infection.
Zonate ring spot symptom. Mature green fruit may not necessarily exhibit any obvious symptoms in the field, however, they may show up as the fruits are ripened (ethylene gas).
A unique ring spot on a fruit a plant affected with tomato spotted wilt. This ring spot looks like Mickey Mouse and was not drawn with a marker. This is a natural ring spot in the same shape.
Another characteristic fruit symptom especially in plants with early infection is fruit cracking and large irregular lesions on green fruits. Fruit cracking symptom can be caused by other reasons also.
While not common, symptoms can also be noticed on varieties with resistance to tomato spotted wilt. In this case, the fruit patterns can be seen on few fruits.
Fruits from TSWV affected plants may exhibit typical concentric circular patters and irregular ripening with yellow blotches at the fruit ripening stage by gasing or during natural ripening.