Plant Protection Quarterly Vol.20(1) 2005 33 industry as S. aurantii could have a major impact on the cost of producing high Australian Scirtothrips aurantii Faure (Thysanoptera: quality, unblemished fruit and major implications for export markets. However, Thripidae) only survived on mother-of-millions the behaviour displayed by S. aurantii in (Bryophyllum delagoense) in a no-choice trial Australia was different from its South African counterpart, as it was only found A.G. MannersA and K. DhileepanB on plants from the family Crassulaceae A CRC for Australian Weed Management, School of Integrative Biology, The (Table 1) and was most often found on B. delagoense. Scirtothrips aurantii was not University of Queensland (UQ), Queensland 4072, Australia. found on any of the ‘known’ host plants Email [email protected] that were in close proximity to infested B Alan Fletcher Research Station, Queensland Department of Natural B. delagoense, e.g. mango and peach. Resources and Mines (QDNRM), 27 Magazine Street, Sherwood, Queensland Therefore we conducted a trial in the field 4075, Australia. on potted plants in order to start testing if S. aurantii would survive on citrus and mango in Australia. It should be noted that at the time of this trial we were unable Summary to conduct experiments under controlled The South African citrus thrips Scir- Laurence Mound (CSIRO) positively conditions, as quarantine restrictions did tothrips aurantii has recently been dis- identified S. aurantii collected by Andrew not allow for transport of the insect. covered in Australia for the first time, Manners and Céline Clech-Goods (QDN- primarily on Bryophyllum delagoense, RM) from Bryophyllum delagoense (Eckl. & Materials and methods a declared noxious weed commonly Zeyh.) Schinz (Crassulaceae), commonly Plants known as mother-of-millions. A prelimi- known as mother-of-millions, a declared The following plant species were used: B. nary study was conducted to ascertain if noxious weed. Scirtothrips aurantii were delagoense, Citrus sinensis (L.) Osbeck (Ru- the Australian population of S. aurantii subsequently found in the quarantine taceae) (navel orange), Mangifera indica L. would survive on citrus or mango in a no facility, probably as a result of using (Anacardiaceae) (mango – see below for choice test. Thrips were placed on potted previously infested B. delagoense to rear cultivars), Syzygium sp. (Myrtaceae) (Aus- plants and surveyed after six weeks. The biocontrol agents inside the quarantine sie Boomer©), and Murraya paniculata (L.) number of S. aurantii in each test plant (Palmer 2005). An attempt was made to Jack (Rutaceae) (orange jessamine). While was recorded, as was any feeding dam- quarantine and eradicate S. aurantii in it was initially planned to use plants that age. Scirtothrips aurantii were recovered 2002 but was discontinued when it was were of similar sizes, this was not possible from B. delagoense only. Further study detected in a large area of Brisbane’s west due to restrictions in the range of what is required to confirm the host status of and southern suburbs on B. delagoense in was available from commercial nurseries. Australian S. aurantii and determine the 2003 (G. Telford 2003 unpublished data). Three cultivars of mango were used: R2E2, relationship between the populations of Furthermore the National Consultative Valencia, and Bowen. All mango and na- S. aurantii in Australia and South Af- Committee on Exotic Plant Pests and vel orange plants were approximately 1 rica. Diseases agreed that S. aurantii was m tall. Bryophyllum delagoense plants, ap- Key words: South African citrus established in South-east Queensland. proximately 40–50 cm tall, were collected thrips, host preference, mother-of-mil- Discovery and persistence of S. aurantii from a site that was not infested with S. lions, Scirtothrips aurantii, Bryophyllum in Australia is of concern for the citrus aurantii; the site had been sampled on delagoense. Introduction The South African citrus thrips, Scirtothrips Table 1. Plant species from Crassulaceae associated with Scirtothrips aurantii Faure (Thysanoptera: Thripidae), aurantii Faure in South-east Queensland. Note that species that had thrips is a serious pest of crops in Africa. In South like damage were located in glasshouses and may not be naturalized in Africa S. aurantii is a pest on citrus and South-east Queensland. Syzy- mangoes and has been recorded on Plant species upon which S. aurantii were positively identified gium sp., peach, asparagus, cotton, castor oil plant, tobacco, bananas, groundnut, Bryophyllum daigremontianum (Raym.-Hamet & Perrier) Berger × B. delagoense (Eckl. & plantain, grapevine, tea, silky oak and Zeyh.) Schinz. (mother of millions) macadamia (Wenztel et al. 1978, de Villiers Bryophyllum delagoense (Eckl. & Zeyh.) Schinz (mother of millions) et al. 1987, Rattan 1995, Childers 1997, Bryophyllum pinnatum (Lam.) Kurz (air plant) Lewis 1997, Gilbert and Bedford 1998) Bryophyllum proliferum Bowie causing leaf malformation and stunted plant growth (Samways 1986, Grové et al. Plant species that had thrips like damage consistent with S. aurantii 2000). More significantly, S. aurantii causes Bryophyllum daigremontianum (Hamet & Perrier) Berger (mother of thousands) blemishes and scars on fruit that decrease Bryophyllum fedtschenkoi (Hamet & Perrier) Lauz.-March (lavender scallops) their grade and value (Wentzel et al. 1978, El Bashir and Al Zabidi 1985, Grout and Crassula arborescens (Mill.) Willd. (silver jade plant) Richards 1990). Crassula argentea cv gollum Thunb. (jade tree) The discovery of S. aurantii during Crassula ovata (Mill.) Druce (jade plant) 2002 on the grounds of the Alan Fletcher Crassula tetragona ssp robusta L. (miniature pine tree) Research Station (AFRS) in Sherwood, Graptopetalum paraguayense (Brown) Walther (ghost plant) a suburb of Brisbane (Queensland, Australia), was of great concern to citrus Kalanchoe gastonis-bonnieri Hamet & Perrier (donkeys ears) growers and other horticultural industries. Sedum nussbaumerianum Bitter (golden sedum) 34 Plant Protection Quarterly Vol.20(1) 2005 multiple occasions and S. aurantii was not Results survived on mango, citrus, Aussie Boomer collected at any time. Aussie Boomer and Approximately 30 individuals (adults and and orange jessamine if they were able to orange jessamine were approximately 30 nymphs not used in the experimental trial) under the conditions of this experiment. cm tall. Aussie Boomer, mango, and or- were used to confirm that the identity of However, this does not mean that S. au- ange jessamine were bought at commer- thrips used were S. aurantii. Therefore we rantii found in Australia could not survive cial nurseries and had not been sprayed assumed that S. aurantii was the only thrips on plants other than B. delagoense under with any chemical for at least one month. species introduced onto test plants. No S. different environmental conditions. Navel orange plants were obtained from aurantii were collected from control plants Another possible explanation for the Dan Smith, Queensland Department of confirming that thrips did not colonise the low numbers of S. aurantii is that the Primary Industries (QDPI). test plants after the experiment was initi- method of transfer of the thrips caused All citrus, Aussie Boomer, orange jes- ated. Therefore the control plants were re- significant mortality. While it is possible, samine and B. delagoense were producing moved from consequent data analysis. and perhaps likely, that the method of new leaves or had new leaves present. Scirtothrips aurantii was recovered from transfer did result in some mortality, all One mango plant was flowering and the B. delagoense only. An average of two (± thrips were transferred in the same man- rest also had new leaves present. Navel 1.14 (one S.E.)) S. aurantii were collected ner. Because we collected S. aurantii on B. orange, mango and Syzygium sp. are all from B. delagoense plants; a total of 10 delagoense we can assume that some thrips known hosts in South Africa (Wentzel et al. thrips were collected from three of the five survived the transfer on the majority, if not 1978, de Villiers et al. 1987, Gilbert and Bed- plants. A total of four thrips were collected all, plants and subsequent mortality was ford 1998); B. delagoense was the only plant from three mango plants (0.8 ± 0.37 (one caused by another factor, i.e. unsuitability species tested that S. aurantii had been col- S.E.)); two Thrips hawaiiensis (Morgan) of the host plant. lected from in Australia. Orange jessamine (Thripidae), one Phlaeothripidae, and one These results tend to confirm the initial was used because it is not a known host Scirtothrips sp. (Thripidae). It is likely that observations that, in Australia, S. aurantii of S. aurantii in any country; presence of the thrips found on mango plants were is not found on some plants that are known S. aurantii on this species would indicate present before the trial began. to be hosts in South Africa. For instance, S. that it could survive on a non-host plant All but one B. delagoense plant exposed aurantii were not present on mango and for relatively long periods. to S. aurantii showed medium to severe peach that were in close proximity to in- thrips feeding damage. All other test fested B. delagoense plants. In another in- Site plants, including control plants, had no stance, citrus plants in close proximity to The experiment was conducted at the Py- visible damage. highly infested B. delagoense were found lara Nursery (Pylara Road, Fig Tree Pock- to be free of S. aurantii (G. Telford 2003 et, Queensland, Australia – 27°31’33”S, Discussion unpublished data). 152°57’30”E) because B. delagoense infest- The results, though preliminary, provide These results are preliminary; they ed with S. aurantii had been discovered some evidence that the population of S. were conducted under quarantine restric- on the property and various quarantine aurantii found in Australia does not sur- tions that did not allow for more rigorous restrictions did not allow us to conduct vive on citrus and mango. methods of testing.