Thrips and Tospovirus in Southern Australia with the Main Emphasis in the Sydney Basin
Swaminathan T, Murdoch G, Clift A
Agricultural Entomology Group, McMillan Building A05, Science Rd, University of Sydney, Sydney, New South Wales 2006, Australia
Correspondence: Stha5139@mail.usyd.edu.au
There are three vector thrips and two Tospoviruses in southern Australia, which is defined as south of latitude 30¡ãS. The vector thrips are onion thrips, Thrips tabaci Lindeman, tomato thrips, Frankliniella schultzei (Trybom) and western flower thrips (WFT) F. occidentalis (Pergande). The Tospoviruses are Tomato Spotted Wilt Virus (TSWV) and Iris Yellow Spot Virus (IYSV). There is a third Tospovirus, Capsicum Chlorosis Virus, which may be vectored by melon thrips, T. palmi Karny, but they both occur in Bundaberg and Childers, south east Queensland, well north of 30¡ãS and will not be considered here. Main host plants are lettuce, potato, peppers, tomatoes and cut flowers such as chrysanthemums. All three vector species occur in the intensive horticultural production near Sydney, Melbourne, Adelaide and Perth. However, in the inland, irrigated production areas, including Crookwell, Hay and Jerilderie, the only vectors are T. tabaci and F. schultzei. WFT was found in Mildura earlier this century and has recently been found in the irrigated areas of Boort, northern Victoria in 2003. The main Tospovirus is TSWV, with IYSV present at on onion seed production areas around Narromine and Griffith. Please refer to the map for the location of these areas. TSWV is vectored by all three vectors, but IYSV is vectored only by T. tabaci. Contrary to popular belief, when infected, F. schultzei is as efficient vector as WFT, but because of its migratory habit, it is less likely to be infected. T. tabaci is intermediate- its is not as efficient vector, but as it moves readily from host to host, especially as weeds dry out during late spring (October/November) it does move the TSWV between both host plants and farms. WFT was first found in Australia in 1993, first in Perth, then Sydney, as two introductions. Its movement has been mainly by infested plant material, often via central markets. In the inland irrigation area, large, overnight flights of F. schultzei can introduce TSWV over a wide area at high levels of infection >80% infection of tomatoes if not sprayed. These flights involving infective thrips occur in about 20% of seasons; T. tabaci is often responsible for lower levels of TSWV, 1¨C25%, but at higher frequency. The major vector in Tasmania, in the Hobart and Launceston area, is T. tabaci, although there are some small, well contained infestations of WFT. In Sydney basin, the flight activity of the thrips population and the presence of TSWV were monitored fortnightly in three commercial horticulture farms. The seasonal dynamics of thrips, their movement pattern within and outside the farm, presence weed hosts for thrips and incidence of TSWV were discussed.
