Tomato spotted wilt tospovirus (TSWV)
English names: Tomato spotted wilt tospovirus (TSWV)
Nordic names: Tomatbronzetopvirus (DK), tomaatin pronssilaikkuvius (FI), Tomatbronsetoppvirus (NO), Bronsfläckvirus (SE)
Major host plants
TSWV is polyphagous on a great number of mostly herbaceous plants and it has one of the widest host ranges of any plant virus. Especially species of Asteraceae, Fabaceae and Solanaceae are recorded as hosts. Weeds may be important reservoirs of TSWV.
TSWV can induce a wide variety of symptoms, which may vary on the same host species with the cultivar, age, and nutritional and environmental conditions of the plant.
On tomatoes, plants show bronzing, curling, necrotic streaks and spots on the leaves. Dark-brown streaks also appear on leaf petioles, stems and growing tips. The plants are small and stunted compared to healthy plants. The ripe fruits show paler red or yellow areas on the skin. Sometimes, affected plants are killed by severe necrosis.
On Capsicum annuum, symptoms are mainly stunting and yellowing of the whole plant. Leaves may show chlorotic line patterns or mosaic with necrotic spots. Necrotic streaks appear on stems extending to the terminal shoots. On ripe fruits, yellow spots with concentric rings or necrotic streaks have been observed.
On the wide range of ornamental hosts, infections are highly variable, but brown necrotic leaf spots and stem streaks are typical, together with chlorotic ring spots or oak-leaf patterns.
The virus is spread world wide.
A map can be downloaded from EPPO’s website. See instructions here.
TSWV is transmitted and spread in nature by thrips (Thysanoptera). They include Thrips tabaci, T. setosus, Frankliniella occidentalis, F. fusca, F. intonsa, F. schultzei and Scirtothrips dorsalis, but the western flower thrips (F.occidentalis) seems to be one of the most effective vectors. The virus is acquired only during larval stages. The vectors are infective 22-30 days after acquisition and often retain the virus for life. The incubation period is 3-10 days, depending on the vector species.
TSWV is liable to spread naturally with its vectors. In international trade, it may be carried by susceptible host plants and will be especially liable to spread if these plants also carry vectors. TSWV is not seed-transmitted.
Detection and inspection
Virus identification requires special laboratory techniques. A commonly used serological test is ELISA. If symptoms suggestive of TSWV appear in the greenhouse at the same time as western flower thrips populations are heavy, it is quite possible that the virus is present.
Pest status and importance
TSWV has become an increasingly important factor contributing to economic losses in many food and ornamental crops throughout the world. Crop losses may be as high as 100%. The introduction and rapid spread of the vector Frankliniella occidentalis in Europe has provided a means of rapid dissemination of this virus, which was previously rare or absent. Its economic importance has rapidly become apparent wherever it occurs on glasshouse crops of ornamentals and vegetables.
Source of information
See further information here:
Author: Jorma Rautapää
Editor: Elise T. Yamamoto Buch