Tomato spotted wilt virus
 Stem streaks and flower distortion on chrysanthemum |
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Tomato spotted wilt virus (TSWV) causes a serious disease and is therefore listed in EC plant health legislation. It has one of the widest host ranges of any plant virus. It can infect over 550 species from about 70 families, including many vegetable and ornamental crops.
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Losses in ornamentals are often 100% because symptoms on leaves and flowers render affected plants unmarketable. Losses in vegetables can be equally damaging when symptoms are present on produce. TSWV will usually kill plants. The virus is found world-wide in countries where its insect vectors are present. It is widespread in Europe, Asia, Africa, North and South America and Australasia. The current UK epidemic started in 1989 and followed the introduction and subsequent spread of western flower thrips in the mid-1980s. The disease is unlikely to develop outside glasshouses in the UK. |
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| How does it spread? |
| The virus and its insect vectors may be introduced on imported
or bought-in infected host plants, whether cuttings or plants in
pots. |
| TSWV is known to be transmitted by seven species of thrips of which two, the western flower thrips (Frankliniella occidentalis), the principal vector, and the onion thrips (Thrips tabaci), are found in the UK. The virus is acquired by the larvae but transmitted to plants by the adults. This transmission can occur after only a few minutes feeding and the adult thrips can be infective for life. TSWV spreads naturally with its vectors, or by movement of infected host plants. It is not normally seed-borne. Weeds such as groundsel and chickweed may be important reservoirs of infection and can harbour the insect vectors. |
| What should I look out for? | |
| On vegetables Symptoms can include stunting and yellowing, chlorotic line patterns, mosaics, necrotic spots, concentric rings, necrotic streaks and distortions. Tomato plants show bronzing, stunting and may be killed by severe necrosis. Leaves may be curled and have necrotic streaks and spots. |
 Necrotic rings on unripe tomato fruit |
 Distorted heart leaves and brown patches on lettuce |
Dark brown streaks may also appear on leaf petioles, stems and growing tips. Ripe fruit may have paler red or yellow areas on the skin. Unripe fruit may develop necrotic rings. On lettuce, infection usually starts on one side of the plant; the leaves become chlorotic with brown patches. The infection spreads to the heart leaves and stops growth on one side of the plant. |
| On ornamentals Symptoms can include stunting, leaf mosaics and mottling, vein clearing, chlorotic spotting, leaf discoloration, ringspots, leaf and stem necrosis, flower breaking and general distortion of the plant. In chrysanthemum there is a wide variation in symptoms among cultivars. Black stem streaks and wilting of the plant are common, but in some cultivars chlorotic and necrotic spots and target rings may also occur. In the New Guinea hybrids of Impatiens there may be black discoloration, or brown spots, at the base of the leaf. |
 Brown spots at base of leaves of New Guinea Impatiens |
| What should I do? | |
| TSWV is notifiable when found on registered premises on the following hosts: |
| Apium graveolens (celery) | Capsicum annuum (sweet pepper) |
| Cucumis melo (melon) | Dendranthema (chrysanthemum) |
| Impatiens (New Guinea hybrids of) | Lactuca sativa (lettuce) |
| Lycopersicon esculentum (tomato) | Nicotiana tabacum (tobacco) |
| Solanum melongena (aubergine) | Solanum tuberosum (potato) |
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Department for
Environment, Food and Rural Affairs 1998 PB 3964 (a) |
CENTRAL SCIENCE LABORATORY |  |
Page last modified:
20 Nov 2006
Page published: 27 May 2004