Thrips can be important pests of capsicum and chilli crops, causing damage through their feeding and by vectoring viral diseases. As different species vary in their ability to transmit viruses and in their susceptibility to insecticides, it is important to know which species are present in a crop. The seasonal occurrence of thrips in capsicum and chilli crops in the Bundaberg district of south-east Queensland was investigated from July 2002 to June 2003. Fifty flowers were collected weekly from crops on seven farms and the adult thrips extracted and identified. Thrips palmi Karny and Frankliniella occidentalis (Pergande) were collected in the greatest numbers, with T. palmi predominant in autumn crops (March to July) and F. occidentalis predominant in spring crops (August to November). Pseudanaphothrips achaetus (Bagnall) was common, while Thrips tabaci Lindeman, Thrips imaginis Bagnall and Frankliniella schultzei (Trybom) were collected in low numbers

Kay, I.

Maltby, J. E.

Nolan, B.

Walsh, B.

English

Queensland DAF eResearch Archive

Plant Protection Quarterly Vol.27(1)  2012   19SummaryThrips can be important pests of capsi-cum and chilli crops, causing damage through their feeding and by vector-ing viral diseases. As different species vary in their ability to transmit viruses and in their susceptibility to insecti-cides, it is important to know which species are present in a crop. The sea-sonal occurrence of thrips in capsicum and chilli crops in the Bundaberg dis-trict of south-east Queensland was in-vestigated from July 2002 to June 2003. Fifty flowers were collected weekly from crops on seven farms and the adult thrips extracted and identified. Thrips palmi Karny and Frankliniella occidentalis (Pergande) were collected in the greatest numbers, with T. palmi predominant in autumn crops (March to July) and F. occidentalis predomi-nant in spring crops (August to No-vember). Pseudanaphothrips achaetus (Bagnall) was common, while Thrips tabaci Lindeman, Thrips imaginis Bagnall and Frankliniella schultzei (Trybom) were collected in low num-bers.IntroductionSeveral species of thrips, principally Thrips tabaci Lindeman, onion thrips, and Frankliniella schultzei (Trybom), to-mato thrips, were long considered minor pests of capsicums and chillis (i.e. pep-pers) (Capsicum annuum L.) in Queens-land. However the significance of thrips as pests of peppers increased following the introduction of Frankliniella occidenta-Seasonal abundance of thrips (Thysanoptera) in capsicum and chilli crops in south-east Queensland, Australia.Bronwyn WalshA,B, John E. MaltbyC, Brendan NolanA,D and Iain KayCA Agri-Science Queensland, DEEDI, Locked Bag 7, MS 437, Gatton, Queensland 4343, Australia. B Current address: Agri-Science Queensland, DEEDI, Bentley Mail Delivery Centre, Western Australia 6983, Australia. C Agri-Science Queensland, DEEDI, 49 Ashfield Road, Bundaberg, Queensland 4670, Australia. D Current address: Education Queensland, 275 North Street, Toowoomba, Queensland 4350, Australia.lis (Pergande), western flower thrips, and Thrips palmi Karny, melon thrips. Frank-liniella occidentalis was first recorded in Australia in 1993 (Malipatil et al. 1993) and at Redland Bay in Queensland in the same year (Kirk and Terry 2003). Franklin-iella occidentalis was commonly found in the Bundaberg district, a major vegetable production district based around the city of Bundaberg (24° 52’ S, 152° 22’ E) by 2001. Thrips palmi, first recorded in Aus-tralia in the Northern Territory in 1989 (Houston et al. 1991), is now widespread in Australia (Persley et al. 2006), and was first recorded in the Bundaberg district in early 2001.Thrips are important pests because they damage capsicums and chillis through their feeding, causing scarring and silvering on fruit, and by transmit-ting the tospoviruses tomato spotted wilt virus and capsicum chlorosis virus that severely affect the plants, resulting in major losses of production (Persley et al. 2006). It is important to know which spe-cies of thrips are present in crops. The species differ in their ability to vector to-spoviruses, so knowledge of the species present allows some estimate of the risk of viral disease occurring. Frankliniella schultzei, F. occidentalis, T. tabaci and T. palmi are vectors of tomato spotted wilt virus, while only T. palmi and F. schultzei are known to vector capsicum chlorosis virus (Persley et al. 2006). Different insec-ticides may be required to control differ-ent species. For example, imidacloprid is effective against T. palmi (Walsh 2004) but is ineffective against F. occidentalis (Kay and Herron 2010). There also are market access issues, with some Australian states requiring that produce imported from Queensland be free from T. palmi.Annually, there are two main capsi-cum and chilli cropping seasons in the Bundaberg district, with some seasonal overlap. Autumn season crops are plant-ed from January to April and harvested from April to August; spring crops are planted from mid-July to September and harvested from October to December.We surveyed the thrips in a number of crops over a 12 month period to de-termine which thrips species are present, and their relative proportion, in capsicum and chilli crops in the Bundaberg district. MethodsSamples were collected from capsicum and chilli crops on seven farms in the Bundaberg district from July 2002 to June 2003. At three of the sites, two crops were grown during the 12 months, while only single crops were grown at the remaining sites. In each crop, 50 open flowers were collected randomly from throughout the crop each week during the crop’s flow-ering period. The flowers were collected into paper bags and returned to the labo-ratory where the thrips were extracted over a white tray. The thrips were placed into 70% alco-hol, and sent to the identification labo-ratory at Gatton Research Station where the adults were cleared by soaking them in 5% NaOH overnight, then gently squashing the thorax and abdomen with a flattened Number 5 pin before rins-ing them in distilled water for 10 min-utes. The cleared thrips were mounted in Hoyer’s solution on microscope slides and identified using taxonomic keys in an unpublished Queensland Department of Primary Industries thrips identification workshop manual compiled by Laurence Mound and John Donaldson.ResultsFigure 1 shows the number of adult thrips of each species collected at each of the farms. Six species were recorded. Frank-liniella occidentalis and T. palmi dominat-ed, and were recorded at all farms and in both cropping seasons. Pseudanaphothrips achaetus (Bagnall), hairless flower thrips, was the next most common species, found on five farms and in both seasons. Thrips tabaci was found in low numbers on three farms in the autumn season and a single Thrips imaginis Bagnall, plague thrips, was recorded. Frankliniella schultzei was recorded in very low numbers at one farm in the spring season.Figure 2 shows the proportions of each species present throughout the year. Thrips palmi was the dominant species from March to July. Frankliniella occiden-talis was common in May-July and domi-Research reports20   Plant Protection Quarterly Vol.27(1)  2012Farm 205101520253035404550Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May JunNo. thrips/50 flowersF. occidentalisP. achaetusnated from August onwards. Pseudan-aphothrips achaetus was recorded com-monly from July to November, although the November collection was from just one farm, with P. achaetus and F. occiden-talis the only species recorded.DiscussionAlthough there was variation between farms in thrips species composition and abundance (Figure 1), a general pattern of occurrence, with T. palmi predominant from March to July and F. occidentalis pre-dominant from August to November, is apparent (Figure 2). Occasional collections (three or four per year) of thrips from pep-per flowers between 2004 and 2011 have confirmed this pattern of species occur-rence (Kay unpublished data).The differences in species occurrence and abundance between farms might be explained by differences in the pest control philosophies and practices on each farm. Crops on Farms 1, 2, 3 and 6, which had almost exclusively T. palmi and F. occiden-talis populations, were weed free and were sprayed frequently to control Helicoverpa spp. and thrips with a range of insecticides including methomyl, spinosad, indoxac-arb, methamidophos and bifenthrin. The Farm 7 crop contained weeds but it was sprayed frequently with insecticides, mainly methomyl and bifenthrin but also methamidophos and spinosad. The diver-sity of thrips species was higher in the crop on Farm 5, which was moderately weedy and sprayed with spinosad, indoxacarb and abamectin less frequently. Farm 4 had the greatest diversity of thrips species. Its crop was heavily infested with a variety of flowering weeds, and was sprayed mainly with Bacillus thuringiensis and very occa-sionally with endosulfan. It seems likely that the minimal use of insecticides and the presence of weeds allows other thrips species to be present and survive, but only T. palmi and F. occidentalis can survive in intensively sprayed crops.Pseudanaphothrips achaetus was recorded from flowers on six farms, and it was com-mon on Farms 4 and 5. Moritz et al. (2004) state that P. achaetus feeds, and apparently breeds in the flowers of a very wide range of plants of different families and that it is widespread throughout Australia. Wil-son and Bauer (1993) recorded it in cotton flowers in the Namoi Valley, New South Wales, and Milne et al. (1997) reported that it is commonly found in stonefruit flow-ers in the Granite Belt area in Queensland. However, there appear to be no reports of it causing damage. It is important to know whether or not its feeding results in dam-age, and this needs to be studied. Even if it is benign, its presence in flowers may result in an insecticide application unless proper identification is carried out.Frankliniella schultzei and T. tabaci can be important crop pests that vector tospovi-Figure 1. Number of thrips recorded from flowers on each farm in 2002-2003.Farm 3050100150200250300350Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May JunNo. thrips/50 flowersF. occidentalisF. schultzeiT. palmiP. achaetusFarm 1020406080100120140160Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May JunNo. thrips/50 flowersF. occidentalisT. palmiPlant Protection Quarterly Vol.27(1)  2012   21ruses (Persley et al. 2006) but were scarce in these collections. A single specimen of T. imaginis was recorded, on Farm 5. It is possible that this specimen was, in fact, Thrips safrus Mound and Matsumoto, the northern plague thrips, which was first described in 2005 (Mound and Masumoto 2005). Mound and Masumoto (2005) state that T. safrus is closely related to, and has previously been identified as, T. imaginis, which it replaces in northern areas. Unfor-tunately the specimen has been lost, so its identity cannot be confirmed.This study has established a general pattern of thrips occurrence in capsicums and chillis in the Bundaberg district, with T. palmi predominant in autumn and early winter and F. occidentalis predominant in late winter and spring. While this informa-tion will help in the management of thrips in crops, it still is essential that crops are checked carefully and the thrips species present identified before management de-cisions are made. There is some variability in the pattern of occurrence and different species may require different management decisions.AcknowledgementsThe study was conducted as part of project VX01018, facilitated by Horticulture Aus-tralia Ltd. (HAL) in partnership with AUS-VEG and funded by the vegetable levy, the Heavy Produce Committee of Queensland Fruit and Vegetable Growers, and Sumi-tomo Chemicals. The Australian Govern-ment provides matched funding for all HAL’s research and development activi-ties. Sandra Dennien and Carolyn Lee as-sisted with thrips identification.ReferencesHouston, K.J., Mound, L.A. and Palmer, J.M. (1991). Two pest thrips new to Aus-tralia, with notes on the distribution and structural variation of other species. Journal of the Australian Entomological Society 30, 231-2.Kay, I.R. and Herron, G.A. (2010). Evalu-ation of existing and new insecticides including spirotetramat and pyridalyl to control Frankliniella occidentalis (Per-gande) (Thysanoptera: Thripidae) on peppers in Queensland. Australian Jour-nal of Entomology 49, 175-81.Kirk, W.D.J. and Terry, L.I. (2003). The spread of the western flower thrips Frankliniella occidentalis (Pergande). Ag-ricultural and Forest Entomology 5, 301-10.Malipatil, M.B., Postle, A.C., Osmelak, J.A., Hill, M. and Moran, J. (1993). First record of Frankliniella occidentalis (Pergande) in Australia (Thysanoptera: Thripidae). Journal of the Australian Entomological Society 32, 378.Milne, J.R., Milne, M. and Walter, G.H. (1997). A key to larval thrips (Thysano-ptera) from Granite Belt stonefruit trees and a first description of Pseudanapho-Farm 60102030405060Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May JunNo. thrips/50 flowersF. occidentalisT. palmiT. tabaciP. achaetusFarm 50510152025303540Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May JunNo. thrips/50 flowersF. occidentalisT. palmiT. tabaciT. imaginisP. achaetusFarm 405101520253035Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May JunNo. thrips/50 flowersF. occidentalisF. schultzeiT. palmiT. tabaciP. achaetus22   Plant Protection Quarterly Vol.27(1)  2012Figure 2. The proportions of each thrips species recorded in capsicum and chilli flowers in south-east Queensland throughout 2002-2003.thrips achaetus (Bagnall) larvae. Journal of the Australian Entomological Society 36, 319-26.Moritz, G., Mound, L.A., Morris, D.C. and Goldarazena, A. (2004). Pest thrips of the world: An identification and information system using molecular and microscopical methods. CD-ROM. (Centre for Biologi-cal Information Technology, Brisbane).Mound, L.A. and Masumoto, M. (2005). The genus Thrips (Thysanoptera, Thripi-dae) in Australia, New Caledonia and New Zealand. Zootaxa 1020, 1-64.Persley, D.M., Thomas, J.E. and Sharman, M. (2006). Tospovirusues – an Austral-ian perspective. Australasian Plant Pa-thology 35, 161-80.Walsh, B. (2004). Managing melon thrips in vegetable crops. Final Report for Horticul-ture Australia Limited Project VX 01018. Sydney, Australia.Wilson, L.J. and Bauer, L.R. (1993). Species composition and seasonal abundance of thrips (Thysanoptera) on cotton in the Namoi Valley. Journal of the Australian Entomological Society 32, 187-92.Farm 7050100150200250300Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May JunNo. thrips/50 flowersF. occidentalisF. schultzeiT. palmiP. achaetusFigure 1. Number of thrips recorded from flowers on each farm in 2002-2003.Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.

Seasonal abundance of thrips (Thysanoptera) in capsicum and chilli crops in south-east Queensland, Australia

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Seasonal abundance of thrips (Thysanoptera) in capsicum and chilli crops in south-east Queensland, Australia

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