Thrips (thysanoptera: Terebrantia) on flowers and fruit of citrus in New Zealand

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1 New Zealand Jurnal f Crp and Hrticultural Science ISSN: 67 (Print) 77 (Online) Jurnal hmepage: Thrips (thysanptera: Terebrantia) n flwers and fruit f citrus in New Zealand R. H. Blank & G. S. C. Gill T cite this article: R. H. Blank & G. S. C. Gill (997) Thrips (thysanptera: Terebrantia) n flwers and fruit f citrus in New Zealand, New Zealand Jurnal f Crp and Hrticultural Science, :, 9, DOI:./ T link t this article: Published nline: Mar. Submit yur article t this jurnal Article views: View related articles Citing articles: View citing articles Full Terms & Cnditins f access and use can be fund at

2 New Zealand Jurnal f Crp and Hrticultural Science, 997, Vl. : 9 67/97/9 $7./ The Ryal Sciety f New Zealand Thrips (Thysanptera: Terebrantia) n flwers and fruit f citrus in New Zealand R. H. BLANK G. S. C. GILL The Hrticulture & Fd Research Institute f New Zealand Whangarei Research Centre Private Bag 9 Whangarei, New Zealand Abstract Thrips were cllected frm flwers, immature and mature fruit frm cmmercial citrus rchards mainly in the Nrthland regin f New Zealand and c. were identified t species. Thrips bscuratus (Crawfrd) cmprised % f all thrips recvered frm flwers f all citrus varieties. Infestatin levels f adults and larvae were cmmnly c. thrips/flwer but they were nt assciated with damage t the rind f fruit. Megalurthrips kellyanus (Bagnall) was als cmmnly fund in flwers, usually in assciatin with T. bscuratus. The highest infestatins f M. kellyanus f thrips/flwer n lemns and thrips/flwer n tangels ccurred at times when T. bscuratus was present at a level f less than thrips/flwer. Apprximately a third f M. kellyanus in flwers were larvae and the remainder were adults indicating that breeding ccurred in the flwers. M. kellyanus larvae were cmmnly fund n immature fruit f lemn, navel range and tangel, where their feeding caused scarring f the fruit. The lw incidence f M. kellyanus n mandarin and Valencia range flwers was reflected in lw numbers f larvae n immature fruit and little evidence f damage. Helithrips haemrrhidalis (Buche) was cmmnly fund n mature fruit f all citrus varieties where their feeding activity caused a whitening f the rind. Fruit f Valencia range were particularly susceptible t damage by this species f thrips, with mandarin, navel range, H97 Received May 997; accepted September 997 and tangel als damaged. The tubuliferan Nesthrips prpinquus (Bagnall) was fund n fruit f all citrus varieties, but there was n evidence f it prducing any damage. Keywrds Thrips bscuratus; Megalurthrips kellyanus; Helithrips haemrrhidalis; Nesthrips prpinquus; citrus; damage INTRODUCTION Thrips are a majr pest f citrus in New Zealand (Cttier 96; Penman 976; Sale 99). Their feeding activity damages the rind f fruit that are cnsequently dwngraded fr bth exprt and dmestic markets. They are als a majr impediment t the develpment f integrated pest management prgrammes n citrus, as cntrl measures are still reliant n the use f rganphsphate insecticides. The rutine use f these bradspectrum insecticides may induce utbreaks f ther citrus pests that wuld nrmally be kept belw damaging levels by predatrs and parasites. Screening trials have identified several ptentially useful materials that may be cmpatible with beneficials but nne have been registered fr use n citrus in New Zealand (Blank & Gill 99). Fur species f thrips have been recrded n citrus in New Zealand (Spiller & Wise 9). The New Zealand flwer thrips, Thrips bscuratus (Crawfrd), is a plyphagus flwerliving species endemic t New Zealand (Mund & Walker 9). Megalurthrips kellyanus (Bagnall) is als a plyphagus flwerliving species first recrded in New Zealand n citrus in 96 and is thught t have riginated in Australia. The greenhuse thrips, Helithrips haemrrhidalis (Buche), is a leaffeeding plyphagus species widespread thrughut the trpics and subtrpics. Nesthrips prpinquus (Bagnall) is a Tubuliferan thrips with a wrldwide distributin and is fund n a wide range f substrates including citrus (Mund & Walker 96).

3 New Zealand Jurnal f Crp and Hrticultural Science, 997, Vl. Thrips damage t citrus fruit has usually been attributed t H. haemrrhidalis (Cttier 96; Penman 976) and it is nly recently that M. kellyanus has been recgnised as a ptential pest f citrus. Bth//, haemrrhidalis andm kellyanus were fund t damage grapefruit and navel range respectively, whereas T. bscuratus did nt damage grapefruit, when high numbers were bagged ver fruit (Hlt 99). The life cycle f T. bscuratus has been described by McLaren & Walker (99). Adults may be fund n flwers all year (Mund & Walker 9). Eggs are laid in flwers where the larval and adult stages feed n nectar and pllen (Teuln & Penman 96; Teuln 9). Pupatin ccurs in the sil and leaf litter. Little is knwn f the bilgy f M. kellyanus. The life cycle f//, haemrrhidalis, n the ther hand, is well knwn (Zndag 977; Mund & Walker 9; Blank & Gill 997). Mixed clnies f adults, larvae, and pupae ccur n a wide range f hsts. Eggs are laid beneath the epidermis f leaves r fruit. When this study was initiated the New Zealand citrus industry recgnised "thrips" as if they were cmpsed f a single species H. haemrrhidalis (e.g., Sale 99), and there was little r n recgnitin that ther species were present and that these culd be invlved in prducing damage t citrus. The main bjective f this survey was t determine which species f thrips ccurred n flwers and fruit f different citrus varieties in New Zealand. This infrmatin in cnjunctin with bservatins n damage can then be used t determine the relative imprtance f the different thrips species. METHODS Citrus rchards were visited during 99,99, and 996 mainly in the Kerikeri and Whangarei areas f Nrthland, but als included sites at Suth Auckland (Site ) and Gisbrne (Site ). Sampling was cncentrated ver the NvemberFebruary perid fr all citrus varieties as well as the March May perid fr lemns when flwers and immature fruit (< mm length), plus mature fruit at sme sites, were present. Additinal visits were made in autumn and winter when mature fruit were examined fr thrips and damage. Orchards were under nrmal cmmercial management, thus sme blcks f citrus received multiple insecticide and fungicide spray applicatins, whereas thers received nly ne r tw fungicide applicatins. The main citrus species and cultivars sampled were: navel range Citrus sinensis Osbeck 'Parent', 'Carter'; Valencia range, C. sinensis 'Harward Late'; lemn Citrus limn Burm. f. 'Yen Ben', 'Villa Franca', 'Gena'; tangel, Citrus paradisi (Macfadyen) x Citrus reticulata (Blanc), 'Seminle'; mandarin Citrus reticulata 'Silverhill', 'Richard's Special', 'Encre', 'Mih', 'Miyagawa', 'Okitsu'; grapefruit (Prman's range) Citrus grandis Osbeck x C. sinensis. At each sampling a small number f flwers and immature fruit were picked at randm and placed in 7% ethanl (Tables ). Large mature fruit were placed in sealed plastic cntainers usually withut ethanl. Fruit n the trees were als examined fr thrips and thrips damage. The symptms f thrips feeding damage was bserved frm fruit infested with thrips and later visits enabled the prgressin f damage t be recgnised even thugh the thrips were n lnger present. Observatins f thrips feeding damage were als supprted by rearing thrips n fruit in the labratry. All stages f//, haemrrhidalis were cntinuusly reared n citrus fruit and M. kellyanus larvae were reared fr several weeks n immature lemn and navel range. Sme lines f fruit were als examined at harvest frm picking bins r during grading in the packhuse. Fruit samples withut ethanl were examined in the labratry within h fr thrips and were usually rinsed with ethanl. Thrips were extracted frm immature fruit and flwer samples by rinsing in ethanl and ensuring calyxes were remved frm fruit, as well as petals frm flwers t free any trapped thrips. Surplus ethanl was remved using a separating funnel. Thrips samples were stred in ethanl in labelled plastic specimen pts. Adult thrips were identified t species using the descriptins f Mund & Walker (9) and cnfirmed using vucher specimens frm the New Zealand Arthrpd Cllectin. Larvae and pupae f//, haemrrhidalis were identified by cmparing with specimens taken frm a labratry clny frm which adults had been previusly identified. Keys fr the identificatin f M. kellyanus and T. bscuratus larvae were nt available althugh sme limited assistance was gained frm drawings f T. bscuratus (Mund & Walker 9) and phtgraphs f M. kellyanus (Hlt 99). Mre imprtantly, nce we had cllected single species specimens f larval M. kellyanus frm lemn fruitlets we were then able t cmpare them with mixed species frm flwers. Larvae f M. kellyanus

4 Blank & Gill Thrips n citrus Fig. Megalurthrips kellyanus larvae (first and secnd instars) feeding n an immature navel range fruitlet. Magnificatin x. and T. bscuratus culd be distinguished n the basis f bdy cnfrmatin and clur. M. kellyanus was yellw r range whereas T. bscuratus was cream clured. M. kellyanus was larger verall and had a larger abdmen and thrax relative t the head cmpared t T. bscuratus. Sme M. kellyanus larvae were als reared thrugh t adults, successfully, in the labratry t cnfirm identificatin. The number and stage f each thrips species was recrded and stred n a database (Micrsft FxPr) alng with site, date, and numbers f flwers r fruit in the sample. Summaries f thrips infesting each citrus cultivar were then cllated frm this database. RESULTS Megalurthrips kellyanus damage M. kellyanus larvae were regularly bserved feeding n small fruitlets f lemn, navel range, and ccasinally tangel. Bth larval stages were visible althugh the small pale clured first instar nymphs were harder t detect than the larger yellw r range clured secnd instars (Fig. ). Grups f up t larvae per fruitlet were bserved. The feeding activity f M. kellyanus larvae remved the green pigmentatin frm the epidermal cells resulting in irregular white patches (Fig. ). Fruit damage varied depending n the numbers f larvae present n individual fruit. Initial feeding activity was ften cncentrated in small depressins n the bdy f the fruit r arund the calyx area and at cntact pints between fruitlets r with leaves. These damaged areas quickly became cvered in a thick scar tissue as the fruitlets grew resulting in a ring f scar tissue arund the calyx and circular, as well as irregular, patches f scar tissue n the bdy f the fruit (Fig. ). Scar tissue spread ver half r mre f the fruit surface n severely damage fruitlets. Much f this damage ccurred n small fruitlets < cm in length s that the scarred areas enlarged as the fruit increased in size. Adult M. kellyanus were bserved n fruit, hwever, as they were generally nly fund in lw numbers there was n evidence f feeding damage. Helithrips haemrrhidalis damage Clnies f//, haemrrhidalis larvae and adults were cmmnly encuntered n all citrus varieties n fruit and leaves. Greater numbers were fund n mature cmpared t immature fruit. Larvae and adults fed n bth leaves and fruit by piercing individual cells and sucking ut the cell cntents (Fig. ). On green fruit and leaves this remved the chlrphyll frm the cells s that they tk n a silvery r white appearance. On mature fruit the remval f the range cartenid pigments resulted in a bltchy white rind. In additin, black spts f faecal material were assciated with recent feeding activity. Clnies f//, haemrrhidalis were ften lcated at cntact pints with ther fruit r leaves (Fig. ). The cncentrated feeding activity at these cntact pints gave rise t characteristic circular spts r rings f scar tissue. Heavily infested fruit

5 New Zealand Jurnal f Crp and Hrticultural Science, 997, Vl. Fig. Megalurthrips kellyanus larvae feeding n a Fig. Characteristic scarring f the rind n immature tangel fruitlet befre the develpment f scar tissue. navel range fruitlets several weeks after the cessatin f feeding by Megalurthrips kellyanus larvae. Fig. Helithrips haemrrhidalis larvae (secnd instars) with distinctive faecal drplet balanced n tip f abdmen, feeding n mature tangel. Magnificatin lox.

6 Blank & Gill Thrips n citrus Fig. Ring spt damage caused by a clny f Helithrips haemrrhidalis at the cntact pint between tw mature Valencia ranges. Fig. 6 Helithrips haemrrhidalis damage t Clementine mandarins at harvest. had large areas f rind damage that, in severe instances, encmpassed the whle fruit. Damage was cmmnly fund n the large mature fruit at harvest (Fig. 6). Valencia range T. bscuratus was the nly thrips species recvered frm Valencia range flwers with an average ver all samples f.7 thrips/flwer (Table ). M. kellyanus was fund at lw levels n immature fruit. H. haemrrhidalis was cmmnly encuntered n leaves as well as fruit. H. haemrrhidalis cmprised 7% f thrips recvered frm immature fruit with an average ver all samples f. thrips/fruit. At these levels % f immature fruit had thrips damage. H. haemrrhidalis cmprised 99% f thrips n mature fruit and averaged. thrips/fruit. H. haemrrhidalis infestatins were higher n mature than n immature fruit. Heavy infestatins f H. haemrrhidalis f up t thrips/fruit were bserved at tw sites in summer and autumn. Damage was cmmn with up t % f fruit affected.

7 New Zealand Jurnal f Crp and Hrticultural Science, 997, Vl. Navel range T. bscuratus was fund infesting navel range flwers at high levels ( thrips/flwer) n fur ut f six sampling ccasins (Table ). T. bscuratus cmprised % and M. kellyanus % f the thrips recvered frm all flwer samples. T. bscuratus and H. haemrrhidalis were generally either absent r at lw levels n immature navel fruit althugh n ne ccasin H. haemrrhidalis was fund at levels f. thrips/fruit. On three ccasins M. kellyanus was fund at levels f.. thrips/fruit when up t % f fruitlets were damaged. H. haemrrhidalis was mre numerus n mature fruit than M. kellyanus. Tw lines f navel fruit were bserved at harvest t have the typical H. haemrrhidalis damage cnsisting f bltchy white areas cntrasting with the range rind. Tangel T. bscuratus was abundant in tangel flwers n mst sampling ccasins during summer but was fund in lw numbers n "ut f seasn" flwers in March and July (Table ). T. bscuratus cmprised 7% and M. kellyanus % f thrips recvered frm flwers ver all sampling ccasins. M. kellyanus was fund at levels f 6 thrips/ flwer n three ccasins in December and cmprised % f thrips. On a further tw ccasins in late January and March M. kellyanus was fund n late flwers at levels f 6 and thrips/flwer and cmprised and 97% f the ttal thrips recvered. Lw numbers f all three species f thrips were recvered frm fruit with M. kellyanus cmprising % f thrips frm immature fruit and H. haemrrhidalis cmprising % f thrips frm mature fruit. N significant damage due t thrips was bserved n these sampling ccasins. Hwever, this des nt truly reflect the susceptibility f tangel fruit t damage by thrips. Fr example, n the February 99 infestatins f up t M. kellyanus larvae were bserved n individual fruitlets causing severe damage (% rind) t unsprayed tangels at Site. Scarring was als bserved arund the calyx n mature fruit Table Numbers f thrips species recvered frm Valencia range ('Harward Late') flwer and fruit samples at selected sampling ccasins. Site Flwers Immature 7 Mature fruit 7 Date Nv 99 Nv 99 7Nv 99 6Nv 99 fruit Nv 99 Dec 99 7Nv 99 Jan Jan Dec 99 Nv 99 7 Nv 99 6Nv 99 6 Dec 99 Samples Megalurthrips kellyanus /sample 6 <. <. <. Thrips bscuratus /sample <. <. <. <. Helithrips haemrrhidalis /sample <

8 Blank & Gill Thrips n citrus cnsistent with feeding damage caused by M. kellyanus larvae in spring. Mature fruit at tw sites were bserved at harvest t have rind blemish caused by H. haemrrhidalis. Mandarin T. bscuratus was cmmnly recvered frm mandarin flwers usually at levels f 9 thrips/ flwer (Table ). M. kellyanus was fund at the tw sites sampled in December 99. Immature mandarin fruits had lw infestatins f thrips and n damage due t thrips was apparent. Mature mandarin fruit were cmmnly infested with H. haemrrhidalis which caused damage t the rind. We bserved several lines f'encre' and 'Richard Special' mandarins at harvest with rind damage as a result f//, haemrrhidalis. Lemn In cntrast t the ther citrus varieties which nly set fruit nce per seasn, lemns set fruit n new grwth flushes which ccur in spring, summer, and autumn. Typically the mst imprtant fruit set ccurs in spring and autumn. T. bscuratus cmprised % and M. kellyanus 6% f thrips recvered ver all flwer samples (Table ). The prprtins f these tw species varied frm t % fr any individual sampling ccasin. The maximum levels f infestatin recrded were 6 thrips/flwer fr T. bscuratus and thrips/flwer frm kellyanus. M. kellyanus was the dminant species fund n immature lemns cmprising 96% f all thrips recvered. The highest levels f infestatin f and thrips/fruitlet ccurred at tw sites that had been left unsprayed befre being sampled in January. At bth sites % f the fruitlets < mm in length were damaged. Individual fruitlets were cmmnly infested with up t larvae, even when the verall average infestatin level was c. thrips/ fruit. Immature lemn fruit were very susceptible t damage by M. kellyanus larvae with scarring ccurring ver a large prprtin f the fruit. A mre intensive sampling carried n May 99 Table numbers f thrips f three species recvered frm navel range ('Parent', 'Carter') flwers and immature fruit samples at selected sampling ccasins. Site Flwers 7 7 Date Dec 99 7Nv 99 6 Dec 99 6Nv 99 6 Dec 99 Nv 99 Immature fruit 7 9 Feb 99 7 Feb 99 6 Dec 99 7 Jan 99 Feb 99 Dec 99 Feb 99 _ Mature fruit 7 7Nv 99 7 Jan 99 9 Nv 99 Samples Megalurthrips kellyanus /sample Thrips bscuratus /sample Helithrips haemrrhidalis 9 9 /sample <. <. <.. <..7...

9 6 New Zealand Jurnal f Crp and Hrticultural Science, 997, Vl. at Site fund % f fruitlets infested with M. kellyanus larvae at an average infestatin f.6 larvae/fruit. Severe thrips damage was fund n 7% f fruitlets including many which n lnger harbured thrips. On average 7% f larvae were fund under the calyx, % at cntact pints, and % n the bdy f the fruitlet. Mature lemn fruit were fund t be infested with bth H. haemrrhidalis and M. kellyanus. Damage t mature fruit caused by H. haemrrhidalis was usually limited t small areas f rind at cntact pints. Life histry stages Adults f T. bscuratus and M. kellyanus were the mst cmmn stage recvered frm citrus flwers Table numbers f thrips f three species recvered frm tangel ('Seminle') flwers, immature and mature fruit samples at selected sampling ccasins. Site Flwers Date 6 Dec 99 Nv 99 Nvl99 Jan Nv 99 6 Dec 99 6 Nv 99 Dec 99 6 Nv 99 Mar 99 Jul 99 Nv 99 Immature fruit 6 6 Mature fruit 6 Feb 99 Nv 99 Dec 99 9 Jan 996 Jan 996 Feb 99 6 Dec 99 Feb 99 Dec 99 Jan 996 Feb 99 9 Jan 996 Mar 99 6 Nv 99 6 Dec 99 Nv 99 7 Nv 99 6 Dec 99 Feb 99 6 Nv 99 6 Nv 99 Samples Megalurthrips kellyanus /sample <. <.. <. Thrips bscuratus /sample < Helithrips haemrrhidalis /sample

10 Blank & Gill Thrips n citrus (Table 6). The relatively high prprtin f nymphs f bth M. kellyanus (6%) and T. bscuratus (6%) fund indicates that breeding was taking place in the flwers. Pupae f T. bscuratus r M. kellyanus were nt fund. The lw numbers f H. haemrrhidalis recvered frm flwers suggest this is nt a preferred lcatin fr this species. Similarly, the lw numbers f T. bscuratus recvered n immature and mature fruit were 7 usually adults and prbably riginated frm flwers that were ften tuching the fruit. Mst f the M. kellyanus recvered n immature fruit were larvae, whereas adults were mre cmmn n mature fruit. On ne ccasin small grups f male and female M. kellyanus were bserved mating n mature lemn fruit. All stages f// haemrrhidalis were fund n immature fruit with adults mre numerus than either larvae r pupae. Table numbers f thrips f three species recvered frm mandarin flwers and immature and mature fruit samples at selected sampling ccasins. Site Flwers lorich.spec. Silverhill Silverhill Silverhill Silverhill 9 Encre Okhitsu Okhitsu Mih 6 Mih Miyagawa 7 Miyagawa 9 Miyagawa Immature fruit Silverhill Silverhill Silverhill Silverhill Silverhill Silverhill Okhitsu Okhitsu Mih Mih 9 Mih Miyagawa Miyagawa Mature fruit lorich.spec. Silverhill 9 Encre Encre Date Nv 99 Nv 99 7 Nv 99 6 Dec 99 6 Nv 99 Nv 99 6 Nv 99 6 Nv 99 6 Nv 99 6 Nv 99 6 Nv 99 6 Nv 99 6 Dec 99 Dec 99 9 Jan 996 7Feb 99 Jan Dec 99 Dec 99 Dec 99 Jan 996 Dec 99 Jan 996 7Feb 99 Dec 99 Jan 996 Nv 99 7 Nv 99 Nv 99 6 Nv 99 _ Samples Megalurthrips kellyanus /sample... Thrips bscuratus /sample Helithrips haemrrhidalis /sample

11 New Zealand Jurnal f Crp and Hrticultural Science, 997, Vl. Table Number f thrips f three species recvered frm lemn flwers, immature and mature fruit samples n selected sampling ccasins. Site Flwers Yen Ben Yen Ben Yen Ben Gena Gena Yen Ben Yen Ben Yen Ben 6 Yen Ben 6 Yen Ben 7 Villa Franca Yen Ben Yen Ben Yen Ben Yen Ben Yen Ben Yen Ben Immature fruit Yen Ben Yen Ben Yen Ben Gena Gena Yen Ben Yen Ben Yen Ben Yen Ben 6 Yen Ben 6 Yen Ben 7 Villa Franca 7 Villa Franca Yen Ben Yen Ben Yen Ben Yen Ben Yen Ben Yen Ben Mature Fruit Yen Ben Yen Ben Yen Ben Yen Ben Yen Ben Yen Ben Date 6 Feb 99 9Nv 99 Dec 99 Mar 99 6 Apr 99 Mar 99 Nv 99 Dec 99 Nv 99 Nv 99 6 Dec 99 6 Dec 99 Nv 99 Dec 99 6 Dec 99 Nv 99 Nv99 9Nv 99 Dec 99 Jan 996 May 99 6 Dec 99 Dec 99 6 Apr 99 May 99 Dec 99 Nv99 Dec 99 Dec 99 9 Jan 996 Nv 99 Dec 99 Jan Dec 99 Nv 99 Jan 996 Mar 99 6 Feb 99 Nv 99 9 Nv 99 Nv 99 Nv 99 Samples Megalurthrips kellyanus /sample < Thrips bscuratus /sample <. <... Helithrips haemrrhidalis /sample 6...

12 Blank & Gill Thrips n citrus Other thrips species The nly ther species f thrips that was cmmnly fund n immature and mature fruit f all citrus varieties was the tubuliferan Nesthrips prpinquus (Bagnall). All stages including eggs, larvae, pupae, and adults were fund. We did nt bserve any damage t the rind f fruit infested with N. prpinquus r any evidence that they fed n the fruit when reared in the labratry. This species, which is cnsidered t feed n fungi r rganic debris, was reasnably abundant and culd be fund at similar levels t M. kellyanus. Fr example, in a sample f 79 immature 'Yen Ben' lemn fruitlets sampled n the February 996, 7 N. prpinquus (. thrips/fruit) and 9 M. kellyanus (.7 thrips/fruit) were recvered. Occasinally, Ceratthrips frici (Uzel) was als fund n sme citrus fruit. E g g.s I tu " S Hel ithrip rips bscura % sta mph Pup; "K u ult Th OJ C ft OH sn. ult a l OOViOO a\ w^ 9 m p l e l O I O CT\ONVOOOOv O MOW O O O OOOOO OIOOO OIOIO DISCUSSION This survey has established the relative imprtance f the main species f thrips present n the main citrus varieties grwn in New Zealand. The survey shwed that the species f thrips respnsible fr damage varies fr different citrus varieties as well as fruit stages. Damage was nt slely due t H. haemrrhidalis as cited in earlier reprts (Cttier 96; Penman 976). Of special interest was the finding that M. kellyanus was an imprtant pest f lemn, navel range, and tangel. This investigatin has therefre extended ur understanding f this thrips as an imprtant damaging agent cmpared t the initial study which fund M. kellyanus damaged navel ranges when high numbers averaging /fruit were bagged ver fruit (Hlt 99). Ceratthrips frici may be cnsidered an infrequent vagrant thrips species n citrus as this species is cmmnly recvered frm yellw flwers f the Cmpsitaceae and is abundant in pasture (Mund & Walker 9). The tubuliferan Nesthrips prpinquus des nt prduce damage t citrus fruit but, as it is fund frm time t time n mature I IX > da m SI s c skel.&. S Si C d : ult cd Pup. E d s "H. E tz) Variety inm c O «O OOOO OOOOO O O I fi^ O O N I <7\min OCN en r O OO(NO<N < m in in C 'S «' mo "C

13 New Zealand Jurnal f Crp and Hrticultural Science, 997, Vl. citrus fruit may achieve significance as a passenger pest f exprt citrus. Althugh this survey was mainly carried ut in Nrthland, with a site in Auckland and Gisbrae, these same species f thrips have als been fund n citrus in the Bay Of Plenty (Blank unpubl. data) and have been recrded n citrus in nrthern regins (Mund & Walker 9,96). It therefre appears that these survey findings apply acrss all the nrthern warmer regins f New Zealand where citrus is grwn. The extensive nature f the survey, which included samples taken ver a wide range f sites, varieties, and times, meant that we had n cntrl ver insecticide applicatins r ther management factrs that might affect thrips ppulatins. We may als have inadvertently sampled sites at times when thrips were unlikely t be present because f extremes f climate r because f the seasnality f life histry stages. This was especially s with M. kellyanus as the phenlgy f this thrips is unknwn. It is therefre imprtant that we interpret ur findings with sme care. Therefre, thrughut this study greater emphasis has been given t findings when thrips were recvered and damage bserved rather than t samples when thrips were at lw infestatin levels. The study shwed that T. bscuratus was the mst cmmn species present in flwers f all citrus varieties cmprising % f all thrips present n Valencia range, 99% n mandarin, 7% n tangel, % n navel range, and % n lemn. Despite infestatin levels cmmnly c. thrips/flwer and the presence f larvae as well as adults we did nt bserve any damage n small fruitlets that culd be attributed t this thrips species. These bservatins are supprted by a trial in which T. bscuratus was bagged ver grapefruit withut damage ccurring (Hlt 99). This cntrasts with the damage caused by T. bscuratus feeding n the develping vary f nectarines that causes russet n fruit (McLaren 99). Hwever, a mre definitive study using different citrus varieties shuld be undertaken t ensure T. bscuratus des nt cause damage t small fruitlets. M. kellyanus was cmmnly fund in flwers, usually in assciatin with T. bscuratus. The highest infestatins f M. kellyanus f thrips/ flwer n tangel and thrips/flwer n lemn ccurred at times when T. bscuratus was less than thrips/flwer. It is prbable that there is cmpetitin between these tw species fr the available pllen and nectar fd resurces. Hwever, in mst circumstances T. bscuratus appears better able t explit the fd resurces in the flwers than M. kellyanus. Cnsequently, T. bscuratus culd be regarded as beneficial if it suppresses the damaging M. kellyanus. M. kellyanus was the mst cmmn thrips species fund n immature fruit f lemn, navel range, tangel and caused significant damage t fruit. There was n evidence, immediately after petal fall, f any feeding damage n lemn, navel range, r tangel fruitlets even when high infestatins f adults and larvae ccurred in the flwers. The cmmencement f damage appeared t cincide with the appearance f larvae several days after petal fall. Cnsiderable damage ccurred at average infestatins >.6 larvae/fruit suggesting that an apprpriate damage threshld at which cntrl measures may be used wuld need t be less than this level if damage is t be prevented. The lw incidence f M. kellyanus n mandarin and Valencia range flwers was reflected in lw numbers n immature fruit during this survey and n evidence f damage. Hwever, further studies are required n sites with unsprayed mandarins t substantiate the pest status f M. kellyanus n this imprtant exprt variety, especially as this thrips was fund n flwers at tw sites in 99. H. haemrrhidalis was cmmnly fund n mature fruit f all citrus varieties. Valencia range fruit were particularly susceptible t damage with heavily infested mature fruit acting as surces f infestatin fr immature fruit. Mature fruit f mandarin, navel range, tangel, and lemn als suffered damage. H. haemrrhidalis is well knwn as a pest f citrus in many citrusgrwing cuntries (Talhuk 97; Lng 96). Valencia range fruit are cnsidered mst susceptible t damage by H. haemrrhidalis in Australia (Beattie & Jiang 99) and Califrnia (Phillips 99), alng with grapefruit in Flrida (Childers & Frantz 99). Descriptins f damage t mature fruit were similar t that which we bserved n Valencia range in New Zealand. In additin, ur study has demnstrated that tangel, navel range, and mandarin fruit are susceptible t damage by H. haemrrhidalis. M. kellyanus has nly been recrded as a pest f citrus in New Zealand. Given that this species is cnsidered t have riginated frm Australia (Mund & Walker 9) we wuld als have expected it t cause damage t citrus there. Steele (9) recrded adults in flwers f citrus and stated that this species was indigenus t Australia because it was als fund in flwers f native plants. Steele

14 Blank & Gill Thrips n citrus als qutes anther persn wh "suspects that M. kellyanus may be the cause f certain skin blemishes f citrus fruits". In a limited survey in Adelaide Btanic Gardens M. kellyanus was recrded frm flwers f tw Australian indigenus plants but nt frm citrus (Kirk 97). This authr als states that it is knwn frm Australian Capital Territry, Queensland, Suth Australia, Victria and there are n recrds f it as a pest. It is f interest that anther clsely related thrips Megalurthrips sjstedti (Trybm) is a pest f cwpea (Vigna unguiculata) flwers in West Africa (Tam et al. 99). There are many similarities between the damage caused by M. kellyanus n citrus in New Zealand and the tw thrips pests f citrus, Scirtthrips citri Mult and Scirtthrips aurantii Faure, that have been extensively studied in Califrnia and Suth Africa respectively. Citrus fruit in all three cuntries are mst susceptible t damage by larvae during the first mnths after petal fall whilst the fruit is < mm (Ann. 99; Grut & Richards 99; Mrse 99). In additin, fruit f navel range and lemn are cnsidered mst susceptible t damage by S. citri (Luck et al. 96; Ann. 99; Phillips 99). Fruit f navel and Valencia range are als cnsidered mst susceptible and mandarin fruit the least susceptible t damage by S. aurantii (Gergala & Stephen 96; Brink 99). The main difference between these thrips is that M. kellyanus is a flwerliving species and it appears that adults need t establish n flwers in rder t breed, whereas bth S. citri and S. aurantii are leafliving species which establish n new fliage as well as n yung fruit (Grut et al. 96; Ann. 99; Brink 99). It is als f interest that citrus flwers in Califrnia are infested with a flwer thrips which disperses after petal fall but des nt damage fruit (Ann. 99). Navel range flwers in Flrida are similarly infested with Frankliniella bispinsa (Mrgan) which has been implicated in restricting fruit set in sme seasns (Childers 99). Bth f these flwerliving thrips appear t ccupy a similar niche t T. bscuratus in New Zealand. This survey has shwn that M. kellyanus and H. haemrrhidalis are the tw thrips species damaging citrus fruit in New Zealand. Hwever, bth the nature and timing f damage were different between species and relates t the different life cycles and explitatin f fd resurces. The key factr fr M. kellyanus appears t be the establishment f adults in flwers where they feed n pllen and/r nectar and prbably lay eggs smewhere in the tissue f the flwer and/r small fruitlets. Althugh larvae were recvered frm flwers mst were fund feeding n immature fruit. Pupae were nt fund in ur citrus samples, suggesting that pupatin may ccur in the sil. Pupae have been recvered frm larvae reared in the labratry. M. kellyanus can prbably nly cmplete a single generatin n mst citrus varieties which flwer in spring and set fruit in early slimmer. Hwever, n lemns that have several flushes f flwers M. kellyanus can cmplete several generatins and build up numbers t becme a persistent pest at sme sites. M. kellyanus was fund t be a relatively spradic and transitry pest that culd rapidly cause severe damage t small fruitlets. In cntrast, H. haemrrhidalis was able t increase in number n leaves and fruit ver the summer s that it was mainly a pest f mature fruit in autumn. This difference in the time that infestatin ccurs significantly alters the expressin f the damage symptms n the fruit. Thus, M. kellyanus larvae nly damage small fruitlets resulting in a heavy scar tissue frming n the rapidly grwing fruit. In cntrast H. haemrrhidalis mainly fed n fully grwn r mature fruit causing disclratin f the rind. Damage by M. kellyanus was therefre ptentially mre severe and difficult t prevent than that caused by H. haemrrhidalis. We cnsider it is imprtant fr grwers t be able t differentiate between thrips species infesting different citrus varieties as cntrl strategies will need t be targeted nly against thse stages and species which cause damage t fruit. ACKNOWLEDGMENTS Our thanks t the many citrus grwers fr allwing us t sample their citrus and t Mrs J. M. Kelly wh extracted thrips frm samples. Our thanks t Dr W. D. Pearsn (MAF Quality Management Lincln) fr identificatin f N. prpinquus. This wrk was supprted by the Fundatin fr Research, Science and Technlgy Cntract CO 6. REFERENCES Ann, 99: Citrus thrips. Pp. 776 in: Integrated pest management fr citrus. Klein, M. ed. Califrnia, University f Califrnia. Beattie, G. A. C.; Jiang, L. 99: Greenhuse thrips and its parasitids in castal New Suth Wales. General and applied entmlgy :.

15 New Zealand Jurnal f Crp and Hrticultural Science, 997, Vl. Blank, R. H.; Gill, G. S. C. 99: Labratry screening f nvel cmpunds against greenhuse thrips Helithrips haemrrhidalis. Prceedings f the th New Zealand Plant Prtectin Cnference:. Blank, R.; Gill, G. 997: Greenhuse thrips. The rchardist 7 (): 79. Brink, T. 99: Cntrl f citrus thrips. Institute fr Trpical and Subtrpical Crps. Infrmatin bulletin n. : 6. Childers, C. C. 99: Suppressin f Frankliniella bispinsa (Thysanptera: Thripidae) and the fungal pathgen Cllettrichum glespriides, with pesticides during the blm cycle and imprved fruit set n navel range in Flrida. Jurnal f ecnmic entmlgy : 9. Childers, C. C.; Frantz, G. 99: Ring spt damage t Flrida citrus fruit caused by thrips feeding injury. Citrus industry, May:. Gergala, M. B.; Stephen, P. R. 96: Evaluatin f synthetic pyrethrids fr the cntrl f citrus thrips Scirtthrips aurantii Faure. Part : Pyrethrids as single spray treatments. Citrus jurnal, June: 7. Cttier, W. 96: Insect pests, Thysanptera. Pp. 9 in: Plant prtectin in New Zealand. Atkinsn, J. D. et al. ed. Wellingtn, Gvernment Printer. Grut, T. G.; Mrse, J. G.; O'Cnnell, N. V.; Flaherty, D. L.; Gdell, P. B.; Freeman, M. W.; Cviell, R. L. 96: Citrus Thrips (Thysanptera: Thripidae) phenlgy and sampling in the San Jaquin Valley. Jurnal f ecnmic entmlgy 79: 6. Grut, T. G.; Richards, G. I. 99: Integrated pest management f citrus thrips (Thysanptera: Thripidae) in the Eastern Cape Prvince f Suth Africa. Prceedings f the VII Internatinal Sciety f Citriculture : 99. Hlt, V. A. 99: Pest status and interrelatinship between three species f thrips present n citrus in the Auckland area. Unpublished MSc thesis, University f Auckland, New Zealand. p. Kirk, W. D. J. 97: A key t the larvae f sme cmmn Australian flwer thrips (Insecta: Thysanptera), with a hst plant survey. Australian jurnal f entmlgy : 7. Lng, S. 96: Thrips n citrusgrves. Pp. in: Integrated pest cntrl in citrusgrves. Cavallr, R.; Di Martin, E. ed. Bstn, Cmmissin f Eurpean Cmmunities, A. A. Balkema. Luck, R. F.; Mrse, J. G.; Mren, D. S. 96: Current status f integrated pest management in Califrnia citrusgrves. Pp. in: Integrated pest cntrl in citrusgrves. Cavallr, R.; Di Martin, E. ed. Bstn, Cmmissin f Eurpean Cmmunities, A. A. Balkema. McLaren, G.F. 99: Thrips n nectarines in the spring. Prceedings f the th New Zealand Plant Prtectin Cnference:. McLaren, G. F.; Walker, A. K. 99: New Zealand flwer thrips, Thrips bscuratus (Crawfrd) life cycle. DSIR infrmatin series n. /. Auckland, New Zealand, Department f Science and Industrial Research. Mrse, J. G. 99: Prspects fr IPM f citrus thrips in Califrnia. Pp. 779 in: Thrips bilgy and management. Parker, B. L.; Skinner M.; Lewis T. ed. New Yrk, Plenum Press. Mund, L. A.; Walker, A. K. 9: Terebrantia (Insecta: Thysanptera). Fauna f New Zealand n.. p. Penman, D. R. 976: Subtrpical fruit pests. Pp. 6 in: New Zealand insect pests. Ferr, D. N. ed. Christchurch, Caxtn Press. Phillips, P. 99: Greenhuse thrips in Califrnia Valencias. Citrgraph 7:. Phillips, P. A. 99: Is the treatment wrth it? Califrnia grwer, July: 9. Sale, P. 99: Citrus pests. The rchardist 6 ():. Spiller, D. M.; Wise, K. A. J. 9: A catalgue (6 96) f New Zealand insects and their hst plants. New Zealand Department f Science and Industrial Research bulletin. 6 p. Steele, H. V. 9: Thrips investigatin. Sme cmmn Thysanptera in Australia. Cuncilfr Scientific and Industrial Research n.. Melburne, Australia. Talhuk, A. S. 97: Citrus pests thrughut the wrld. Pp. in: Citrus. Technical mngraph n.. Switzerland, GibaGeigy Agrchemicals. Tam, M.; Baumgartner, J.; Delucchi, V.; Herren, H. R. 99: Assessment f key factrs respnsible fr the pest status f the bean flwer thrips Megalurthrips sjstedti (Thysanptera: Thripidae) in West Africa. Entmlgical research :. Teuln, D. A. J. 9: Pest management f the New Zealand flwer thrips Thrips bscuratus (Crawfrd) (Thysanptera: Thripidae) n stne fruit in Canterbury, New Zealand. Unpublished PhD thesis, Lincln Cllege, University f Canterbury, New Zealand. Teuln, D. A. J.; Penman, D. R. 96: A rearing methd fr the New Zealand flwer thrips. Prceedings f the 9th New Zealand Weed and Pest Cntrl Cnference:. Zndag, R. 977: Greenhuse thrips Helithrips haemrrhidalis (Buche) (Thysanptera: Thripidae). Frest and timber insects in New Zealand n.. Rtrua, Frest Research Institute, New Zealand Frest Service.