YOUR PRODUCTION
3 SYMPTOMS of TSWV on tomatoes — purpling and ringspots. 1
Tomato spotted wilt virus affecting tomato fruit 2
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BY DR CRAIG WEBSTER DEVELOPMENT OFFICER, DPIRD
omato spotted wilt virus (TSWV) is a serious disease of many vegetables including tomato, capsicum and chilli but many other vegetables and weeds can also be infected (over 900 hosts are known).
3 ADULT western flower thrips feeding on bean leaves have caused the mottled effect.
These include common weeds like nightshade and cape weed, which often don’t show very strong symptoms. These plants provide a local source of the virus that allow it to spread into nearby crops. Symptoms of the virus vary but include necrosis, purpling and ringspots on the fruit and new leaves of infected plants. The ringspots are the
most common symptom in capsicum and chilli and are seen on the fruit and leaves. These symptoms impact on fruit marketability and can lead to losses of 100%, especially when young plants are infected before fruiting. In tomatoes, ringspots are only seen on fruit and symptoms on leaves but may be absent in resistant varieties.
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WA Grower WINTER 2020
The virus is spread by thrips which, apart from spreading the virus, also directly cause damage to plants they feed and lay eggs on. Many species of thrips can spread the virus but in Western Australia, the main ones are the western flower thrips (WFT), tomato thrips and onion thrips. The rate that they spread the virus is different for each species so it is important to know which ones are present. Others, such as the plague thrips, are not known to be able to spread the virus. Adult and larvae thrips are usually found inside flowers or on the underside of leaves and cause silvery flecked scars with small black faecal spots. Thrips cannot be identified by eye and require specialists to identify the species.
