Bio-ecology and Control of Pezothrips kellyanus (Thysanoptera: Thripidae) on Citrus in Cyprus

Transcription

1 The Europen Journl of Plnt Science nd Biotechnology 2008 Globl Science Books Bio-ecology nd Control of Pezothrips kellynus (Thysnopter: Thripide) on Citrus in Cyprus Vssilis A. Vssiliou * Agriculturl Reserch Institute, Plnt Protection Section, P.O. Box 22016, 1516 Nicosi, Cyprus Correspondence: * vssilis@rinet.ri.gov.cy ABSTRACT Kelly s citrus thrips is one of the most common thrips species found in Cyprus citrus orchrds. Kelly s citrus thrips lrve were the sole insect stge cusing feeding dmge minly on immture lemon nd grpefruit fruits. Under Cyprus conditions Kelly s citrus thrips dults prefer to concentrte mostly in the northern nd estern sides of both lemon nd grpefruit cnopies. The recorded men number of dults in the northern side of lemon cnopies ws 60.7, followed by estern 48.4 dults (F 0.05 (3, 32) = 2.431; P< 0.083; Men sq. = ), while on grpefruit cnopies ws 45.3 nd 30.8 dults (F 0.05 (3, 32) = 4.237; P< 0.012; Men sq. = ) in the northern nd estern sides, respectively. In 2006, dmge of lemon nd grpefruit fruits reched 64.0% nd 45.8%, respectively, while in 2007 dmge ws recorded t 50.4% nd 91.2%, respectively. Depending on wether conditions nd pest s bundnce, the first chemicl sprying should be pplied dys fter mssive petl fll nd clyx closure t the fruitlet stge, nd the second one-two weeks fter the first ppliction. Vrious insecticides were evluted in field trils in lemon nd grpefruit plnttions ginst Kelly s citrus thrips. Sttisticlly significnt differences were observed in 2006 nd In 2006, the best protection of lemons provided by the neonicotinoid cetmiprid (93.0%) nd the crbmte methiocrb (79.7%), while on grpefruits the most effective insecticides were cetmiprid (95.1%) nd the mcrocyclic lctone spinosd (75.7%). In 2007, cetmiprid nd the Insect Growth Regultor lufenuron provided 85.1% nd 82.2% protection of lemons, respectively, while on grpefruits best results were obtined with cetmiprid nd the orgnophosphte chlorpyrifos providing 86.5% nd 84.1% protection, respectively. Keywords: chemicl control, dmge, distribution, grpefruit, insecticides, lemon INTRODUCTION Citrus is one of the most importnt crops in Cyprus. The re under citrus is bout 5543 h, representing 4.1% of the totl cropped re nd 15% of the irrigted lnd. The min citrus vrieties cultivted in Cyprus re: ornges %, lemons %, grpefruits %, mndrins nd other vrieties - 16%. The Interntionl literture provides very scrce informtion bout the biology, the ecology nd the mngement of Kelly s citrus thrips (KCT) s this is new pest. The min objective of this work ws to study the bioecologicl peculirities nd test vrious insecticides for the control of KCT under Cyprus field conditions. In this study, we present the results of the crdinl distribution nd the efficcy of vrious ctive ingredients of insecticides ginst KCT, pplied in lemon nd grpefruit orchrds. Kelly s citrus thrips (KCT) Pezothrips kellynus (Bgnll) becme n economic pest on citrus plnttions in Cyprus in the lst decde. The pest ws recorded for the first time in 1996 in the costl citrus plnttions of the Limssol nd Pphos districts nd cused serious dmge (scrring round the clyx), minly on lemon nd grpefruit fruits (Orphnides 1998). The pest ws lso recorded in Austrli in 1914 (Bgnll 1916), in New Zelnd in 1950 (Mound nd Wlker 1982), in Greece in 1981 (Plmer 1987; zur Strssen 1986), in Turkey nd Spin (zur Strssen 1996), in Southern Itly (Mrullo 1998), in Portugl (zur Strssen 2003), nd Southern Frnce (Moritz et l. 2004). In these countries, KCT cuses serious dmge on citrus fruits every yer. It remins uncler if the pest is species of Europen citrus tht ws introduced into Austrli or ws n Austrlin endemic pest tht chnged its host ssocitions nd hbits, nd recently migrted to Europe. The Austrlin host plnt dt revel tht the pest is n Austrlin ntive insect (Webster et l. 2006). Limited informtion is vilble bout the biology nd mngement nd this is becuse KCT is reltively new citrus pest. P. kellynus is polyphgous flower-living species. The femles ly eggs on flower prts, minly in the LARVAE EGGS ADULT DAMAGED FRUIT PUPAE Fig. 1 Life cycle of Kelly s citrus thrips Pezothrips kellynus. Life cycle of KCT consists of eggs, two lrvl stges (I nd II), pre-pupe, pup nd dult. The informtion we provide regrding KCT s life cycle is not result of our reserch but it is obtined from vilble studies tht conducted in Austrli nd New Zelnd. Development stges of KCT nd their durtion depend on the seson. In spring, the verge number of dys required for the development of one genertion is bout dys, in summer -14 nd in winter KCT dults re in high numbers in spring during the min flowering period of citrus. Received: 1 April, Accepted: 13 April, Originl Reserch Pper

2 The Europen Journl of Plnt Science nd Biotechnology 2 (1), Globl Science Books petls (Fig. 1). The pest puptes exclusively in the soil (Jmieson nd Stevens 2006; Webster et l. 2006). After emerging in the spring, dults nd lrve feed on pollen nd nectr. There re two lrvl instrs - I nd II. KCT bundnce peks in citrus orchrds during the min flowering period in spring (Bker et l. 2002). This species develops up to six genertions per yer (EPPO 2004). The pest prefers to feed in sheltered res such s under the clyx, between touching fruit, nd where lef or twig touches the fruit. In serious cses of dmge, the scrring cn cover the entire fruit. Lemons pper to be the most importnt source nd refuge for KCT nd this is due to their spordic flowering throughout the yer. Low popultions of KCT hve been recorded on mndrin nd Vlenci ornge flowers (Blnk nd Gill 1997). Since its ppernce, KCT hs become serious citrus pest in Cyprus, cusing scrring dmge on citrus fruits (Orphnides 1998). The dmge is cused by the two lrvl instrs. This species feeding on immture fruit cuses silvery, ring-like form thin lyer of scrring (hlo) on the fruit surfce, minly round the clyx re of the developing fruit-let. Lemons pper to be very susceptible to P. kellynus (Froud et l. 2000), followed by ornges (nvel nd Vlenci) nd grpefruit (Bker et l. 2004). In New Zelnd, KCT lrve were commonly found on immture lemon fruits, nvel ornge nd tngelo. In Greece, 70% of citrus fruits in Chni (Crete, Greece) showed typicl scrring dmge cused by KCT (Vrikou et l. 2002). In estern Sicily, the lrve hve cused serious feeding dmge on immture fruits of lemons nd ornges (Conti et l. 2001). Despite the insecticide pplictions (one to five) ginst KCT, n verge of 20 40% of the fruit cn remin unsleble to the fresh fruit mrkets (Bker 2007). Infested fruits re considered uncceptble for export, even though the presence of the scrs ffects only the ppernce nd not the qulity of the fruit. KCT popultions in citrus orchrds cn be reduced with insecticides (Bker et l. 2004; Mrtin 2005; Vssiliou 2007) nd some soil-dwelling predtory mite species nd prsitoid insects (Bker et l. 2005). Relince only on insecticides cn led to development of resistnce. Resistnce to chlorpyrifos hs been reported from South Austrli, resulting in field control filures (Purvis 2002). MATERIALS AND METHODS This reserch ws conducted t the Achelei Experimentl Sttion in the Pphos district (Western costl re of the islnd) in The Experimentl citrus plnttions t the Sttion cover n re of 10 h. The min citrus vrieties smpled for KCT presence were the following: Citrus sinensis Osbeck - ornges (common, nvel, red), Citrus prdisi Mcf - grpefruits - (red nd white), Citrus mxim (Burm) - pummelo, Citrus reticult Blnco mndrins, Citrus limon Burm. - lemons, nd Citrus medic Linn. - citron. Cnopy distribution The distribution of thrips on lemon nd grpefruit trees cnopy ws studied. The min smpling nd observtions were gthered from lte Februry to lte June, minly on mture lemon (19 yers-old) nd grpefruit (17 yers-old) trees. Counts of thrips in flowers were conducted weekly on 10 rndomly selected trees in the lemon nd grpefruit orchrds (2 nd 3 h, respectively). From ech tree, 40 rndomly distributed flowers from the periphery of the cnopy (10 from the estern, 10 from the southern, 10 from the northern nd 10 from the western sides) were exmined (without removing them) for the presence of dult thrips, using 10X hnd lens. These counts were initited in erly spring when the first flowers on the lemon nd grpefruit trees ppered nd lsted until the end of flowering. Insecticide field trils nd fruit dmge evlution The chemicl pplictions were conducted in lemon nd grpefruit vrieties only. The plnting distnces were s follows: lemons 8 8 m; grpefruits 8 5 m. No buffer trees were used. In lemons there were totl of 11 tretments - 10 tretments with the ctive ingredients tested nd 1 tretment used s control (no insecticides were pplied). Ech tretment included 1 row of 12 trees with two replictions. In grpefruits there were totl of 12 tretments 11 tretments with the ctive ingredients tested nd 1 tretment used s control (no insecticides were pplied). Ech tretment included 1 row of 16 trees with two replictions. All ctive ingredients were pplied in erly morning nd in full clmness (no wind) in order to void insecticide drifting. The first ppliction in grpefruits (2 My, 2006; 7 My, 2007) nd lemons (3 My, 2006; 8 My, 2007) ws conducted during the mssive lrve ppernce tht coincides with the fruit-let formtion, nd the second one, two weeks fter the first ppliction (lemons 16 My, 2006 nd 22 My, 2007; grpefruits 15 My, 2006 nd 21 My, 2007, respectively). Insecticides tht hve been tested every yer nd found to hve low effectiveness ginst KCT were replced with other ctive ingredients. In order to evlute the efficcy of the pplied insecticides, two insecticide pplictions with the sme ctive ingredient were conducted s follows: the first one, dys fter mssive petl fll (t fruit-let formtion) by sprying ll trees on the rows, nd the second one, two weeks fter the first ppliction, by sprying hlf the number of trees in the row for comprison. For ppliction of insecticides high pressure pplictor Unifrm (Udor Srl, 42048, Vi A. Corrdini 2, Rubier, Itly) with cpcity of 500 L ws used. The tnk is equipped with two hoses of 50 m ech nd Gmm-95 high pressure plunger pump (mximum pressure 60 br; flow rte 73.5 L/min). The chemicl pplictions hve been conducted by using simultneously two high pressure sprying guns with stndrd nozzle (2 mm) for generl folige sprying of insecticides. Approximtely 25 L of spry per tree ws pplied nd the sprying pressure used in our trils ws 2.5 brs. During hrvesting in December, dmge cused by KCT ws evluted by selecting rndomly one hundred fruits from the boxes (collected from ech tree in the tretment nd the control) nd exmining them for scr dmge, minly round the clyx. Scrs were clssified s either slight or severe ( severe scr ws ny tht would cuse the fruit to be not suitble for export). Insecticides All ctive ingredients used in field trils were commercilly vilble nd hve pprovl for use in citrus ginst vrious pests. The commercil product bsed on entomopthogenic fungi Beuveri bssin is registered for use s biologicl insecticide. Appliction rtes used in field trils were those recommended on the lbel by the mnufcturer. All insecticides nd the ppliction rtes used in field trils in re presented in Tble 1. Sttisticl methods All sttisticl nlyses nd comprisons were performed by SAS (SAS 2002). Becuse of unequl subclss numbers, GLM procedure ws employed to nlyse the dt. Men (P< 0.05) comprisons were performed using the Tukey s test. In order to normlize the dmge percentge, the ARCSINE trnsformtion ws dopted to trnsform the rel dmge. RESULTS Cnopy distribution Direct smpling of lemon nd grpefruit flowers conducted in 2006 nd 2007 indicted tht the distribution of thrips in the cnopy ws not uniform; the pest prefers to concentrte mostly in the estern nd northern sides of the cnopy (Tble 2). The results from the sttisticl nlysis reveled significnt differences in KCT s crdinl distribution on lemon nd grpefruit cnopies in The recorded men number of dults in the northern side of lemon cnopies ws 60.7, followed by estern 48.4 dults (F 0.05 (3, 32) 70

3 Kelly s citrus thrips on citrus in Cyprus. Vssilis A. Vssiliou Tble 1 Insecticides nd ppliction rtes used in field trils ginst Kelly s citrus thrips in Achelei Experimentl Sttion. Yer Active ingredient Commercil nme Compny Dose b g.i. L chlorpyrifos Dursbn 48% EC DowAgroSciences, Indinpolis, USA 1.5 cc lufenuron Mtch 5% W/V Syngent, Mdrid, Spin 1.5 cc methiocrb Mesurol 75 WP ByerCropScience, Leverkus., Germny 2.0 g dizinon Bsudin 600 EC Syngent, Mdrid, Spin 1.5 cc methomyl Lnnte 90 SP DuPont, Newrk, USA 0.6 g dichlorvos Divipn 100 EC Mkhteshim Agn, Omer, Isrel 1 cc crinthrin Rufst 6 EC Cheminov, Lemvig, Denmrk 1 cc spinosd Trcer 48% EC DowAgroSciences, Indinpolis, USA 0.3 cc cetmiprid Mospiln 20SP Nippon Sod, Shrd, Jpn 0.5 g B. bssin Nturlis L Troy Biosciences Inc, Arizon, USA 1.5 cc thimethoxm Actr 25 WG Syngent AG, Bsel, Switzerlnd 0.15 g bmectin Vertimec 1,8% EC Syngent AG, Bsel, Switzerlnd 0.5 cc prffinic oil U.F. Oil, 98.8% Sun Compny Inc., Phildelphi, USA 6 cc g L -1 of sugr hs been dded to this ctive ingredient b L -1 of wter Tble 2 Cnopy distribution of Kelly s citrus thrips on 10 lemon nd 10 grpefruit trees by exmining 40 flowers from the periphery (10 from ech of the crdinl direction). Achelei Experimentl Sttion, Side KCT dults Lemon b Grpefruit c North Est 48.4 b 30.8 b South 28.4 b 15.0 b West 24.1 b 9.9 b Mens within ech column with the sme letter re not significntly different t 5%, ccording to Tukey s Test. b F 0.05 (3, 32) = 2.431; P< 0.083; Men sq. = c F 0.05 (3, 32) = 4.237; P< 0.012; Men sq. = = 2.431; P< 0.083; Men sq. = ), while the recorded men number on grpefruit cnopies ws 45.3 nd 30.8 dults in the northern nd estern sides, respectively (F 0.05 (3, 32) = 4.237; P< 0.012; Men sq. = ). No sttisticlly significnt differences on cnopy distribution were observed between the southern nd western sides on both the lemon nd grpefruit cnopies. Insecticide field trils nd fruit dmge evlution During , series of insecticides with different mode of ction were evluted, iming to find the most effective in controlling the KCT popultions nd reducing the dmge in lemons nd grpefruits cused by this pest. KCT popultions in lemons nd grpefruits during the exmined yers were present in high numbers tht could cuse serious dmge (Fig. 2). This finding ws result of the popultion monitoring nd trpping which hs conducted in experimentl nd commercil citrus orchrds, minly in lemon nd grpefruit vrieties. Dmge (%) Lemons Grpefruits Yer Fig. 2 Dmge of lemons nd grpefruits in control tretments in The insecticides found so fr to be the most effective fter two pplictions ginst KCT re shown in Tble 3. The level of efficcy of the pplied insecticides hs been observed to vry yer-by-yer in lemons nd grpefruits. The sttisticl nlyses showed tht the tretment differences in yers 2006 nd 2007 were highly significnt. In 2006, cetmiprid nd methiocrb gve the best results providing 93.0% nd 78.7% protection of lemons, respectively (P< ; trnsformed dmge - F 0.05 (10, 83) = 9.82; rel dmge - F 0.05 (10, 83) = 6.87), while on grpefruits the best results were obtined from cetmiprid nd spinosd providing 95.1% nd 75.7%, respectively (P< ; trnsformed dmge - F 0.05 (11, 166) = 8.94; rel dmge - F 0.05 (11, 166) = 5.76). Other ctive ingredients such s chlorpyrifos (net) nd lufenuron provided 46.3% nd 72.8% protection of lemons nd grpefruits, respectively. In 2007, crinthrin gve the best results providing 85.1% protection of lemons, followed by lufenuron with 82.2% protection (P< ; trnsformed dmge - F 0.05 (10,89) = 8.54; rel dmge - F 0.05 (10,89) = 8.27), while on grpefruits the best protection 86.5% ws given by cetmiprid, followed by chlorpyrifos (net) with 84.1% protection (P< ; trnsformed dmge - F 0.05 (11, 160) = 37.77; rel dmge - F 0.05 (11, 160) = 41.70). DISCUSSION Flower smpling in the field showed tht KCT is n ctive pest tht prefers to concentrte mostly in the estern nd northern sides of both lemon nd grpefruit cnopies. The blooming in lemon trees, compred to grpefruit nd other citrus vrieties, is not uniform. The experimentl trils hve shown tht crdinl direction ppered to hve significnt effect on species distribution on the cnopy. The two likely explntions tht cn be offered for this phenomenon re the following: the first one is tht these sides of the cnopy (estern nd northern) re in shdowed res most of the time throughout the dy nd KCT dults void direct sunlight, especilly when the tempertures re high; the second one is tht this higher concentrtion perhps hs to do more with the wind direction nd speed. On the islnd of Cyprus, minly in the costl res where the mjority of citrus re grown, frequent nd reltively high west nd south-west winds blow, minly during spring (flowering period) nd summer. South nd south-west winds were predominnt t the tril site of the Experimentl Sttion over the course of this study. Other investigtors (Lewis 1997) hve shown tht thrip s flying ctivity nd directionlity of flight is strongly influenced by tmospheric conditions, minly by wind direction. Obviously, KCT dults re concentrting mostly on estern nd western sides of the cnopies in order to void direct wind. These observtions will be further studied in detil t lter time, in conjunction with the fruit dmge cused by KCT on these sides. Since 1996, when the pest ws first found in Cyprus citrus groves, mny field trils were conducted iming to determine the most optimum timing for sprying. The insecti- 71

4 The Europen Journl of Plnt Science nd Biotechnology 2 (1), Globl Science Books Tretment Tble 3 Insecticide effectiveness ginst Kelly s citrus thrips on lemons nd grpefruits (combined results from two replictions). Achelei Experimentl Sttion. Citrus species Tretment Dmge Dmge Rel Trnsf. b Rel Trnsf. c Lemon dichlorvos bmectin dizinon dichlorvos lufenuron chlorpyrifos d 55.9 b 7.2 b control methomyl 52.0 b 7.0 b spinosd e chlorpyrifos (net) 51.9 b 7.0 b chlorpyrifos (net) control 50.1 bc 6.9 b B. bssin spinosd e 38.6 bcd 6.1 bc methomyl 55.4 b 7.1 thimethoxm 27.0 bcd 4.6 bc chlorpyrifos d 53.7 b 7.1 cetmiprid 19.0 cd 4.0 c methiocrb d 21.3 bc 4.2 b lufenuron 17.8 cd 3.9 c cetmiprid 7.0 c 2.4 b crinthrin 14.9 d 3.7 c Grpefruit control control dichlorvos b lufenuron b dizinon b dichlorvos 56.9 b 7.5 bc chlorpyrifos (net) b crinthrin 56.8 b 7.5 c chlorpyrifos (net) b clorpyrifos (net) 50.3 b 6.9 c B. bssin b spinosd 49.2 b 6.9 c chlorpyrifos d b bmectin 44.4 bc 6.6 cd ethiocrb d b methomyl 30.3 cd 5.3 de methomyl b thimethoxm 24.7 d 4.9 ef lufenuron b chlorpyrifos d 23.0 d 4.7 ef spinosd e 24.3 b 4.7 b chlorpyrifos 15.9 d 3.8 f cetmiprid 4.9 b 2.0 c cetmiprid 13.5 d 3.6 f Mens within ech column with the sme letter re not significntly different t 5%, ccording to Tukey s Test. b In lemons, the F vlues for the trnsformed nd rel dmge for 2006 were: F 0.05 (10, 83) = 9.82; F 0.05 (10, 83) = 6.87; P< , respectively, nd for F 0.05 (10,89) = 8.54; F 0.05 (10,89) = 8.27; P< , respectively. c In grpefruits, the F vlues for the trnsformed nd rel dmge for 2006 were: F 0.05 (11, 166) = 8.94; F 0.05 (11, 166) = 5.76; P< , nd F 0.05 (11, 160) = 37.77; F 0.05 (11, 160) = 41.70; P< for 2006 nd 2007, respectively. d To these ctive ingredients, 5.09 g.i. L -1 of Ultr Fine Oil ws dded. e To this ctive ingredient, 2.54 g.i. L -1 of Ultr Fine Oil ws dded. cides were pplied in different stges of flowering nd fruitlet formtion. Very low or no effect on KCT popultions ws observed when chemicls were pplied in 50% of flowering nd full flowering (Chrlmpous, P pers. comm.) of lemon nd grpefruit species. During these flowering stges, the incidence of KCT lrve is very limited. The vribility in effectiveness of vrious insecticides both in lemons nd grpefruits throughout the exmined yers cn be explined by previling wether conditions (such s strong winds, rin, nd low night tempertures) tht tke plce during the flowering period in the experimentl re. Three bsic fctors were tken into considertion in order to determine the most suitble timing of pplictions: ) the mssive presence of lrve, b) the flowering stge of the vriety nd its durtion nd, c) the bsence of wind. Under Cyprus conditions, the most crucil period for dmge is during the first dys fter petl fll to clyx closure (Vssiliou 2007). The durtion of this stge vries yer by yer nd depends exclusively on wether conditions. All insecticides were pplied 2-3 weeks fter mssive petl fll nd minly ginst the lrvl stges (instrs) I nd II. Fruit dmge depends lso on pest density. KCT s popultion density ppers to depend on the citrus vriety, the presence nd bundnce of flowers, nd the durtion of flowering stge. Popultion densities of KCT in citrus groves re very high during the min flowering period nd very low during the winter seson. The flowering stge of grpefruits is more uniform, short nd simultneous compred to the flowering stge of lemons which is not uniform, nd is long-lsting. Lemon vrieties flower spordiclly throughout the yer, nd pper to be n importnt feeding source nd refuge for KCT popultions. According to our results no significnt differences in dmge of both the untreted lemon nd grpefruit fruits cused by KCT were observed. The only exception ws observed in 2005 where dmge in lemons ws pproximtely 18% higher compred to grpefruits while in 2007, dmge in grpefruits ws pproximtely 41% higher compred to lemons (Vssiliou 2007). Other investigtors (Mrullo 1998; Conti et l. 2001; Vrikou et l. 2002; EPPO 2004) hve shown tht dmge cused by KCT in lemons is more severe thn in other citrus crops. The very good protection of lemons nd grpefruits obtined by some ctive ingredients such s cetmiprid, lufenuron, chlorpyrifos, spinosd, nd crinthrin ws probbly the result of interply of fctors ffecting the popultion densities of the pest nd minimising the dmge risk. Before conducting the chemicl pplictions the following fctors were considered: 1) tht the pek of the mssive ppernce of lrve ws identified (fter detiled scouting nd trpping). The length nd intensity of the scurfing risk period vries from yer to yer due minly to vrition in pest s bundnce. Bsed on tht, the chemicls were pplied only during the mssive ppernce of lrve; 2) tht previling wether conditions, minly the bsence of rin nd wind were known. As it ws stted erlier this species prefers to concentrte mostly in the northern nd estern sides of the cnopy. This is likely the result of strong winds tht previl in the islnd every yer minly during the citrus flowering period in spring, nd 3) tht ll ctive ingredients tht could be used in trils, should hve pprovl for use in citrus nd lbels indicting their effectiveness ginst different thrips species. During the exmined yers, we observed tht the popultions of vrious insect pests incresed fter two pplictions with some insecticides. Outbrek of Cliforni red scle Aonidiell urntii (Mskell) (Homopter: Dispidide), cottony cushion scle Icery purchsi (Mskell) (Homopter: Mrgrodide), nd citrus melybug Plnococcus citri (Risso) (Hemipter: Pseudococcide) on lemons nd grpefruits ws observed fter tretment with thimethoxm. Outbrek of citrus rust mite - Phyllocoptrut oleivor (Ashmed) (Acri: Eriophyide), citrus wooly whitefly - Aleurothrixus floccosus (Mskell) (Homopter: 72

5 Kelly s citrus thrips on citrus in Cyprus. Vssilis A. Vssiliou Aleyrodide), orientl spider mite Eutetrnychus orientlis Klein (Acri: Tetrnychide), nd Cliforni red scle Aonidiell urntii (Mskell) (Homopter: Dispidide) ws observed fter two tretments with cetmiprid. High popultions of purple scle Lepidosphes beckii Newmn (Homopter: Dispidide) hve been recorded fter two consecutive yers of tretment with methomyl. Similr sitution ws observed with Cliforni red scle Aonidiell urntii (Mskell) fter two tretments with spinosd. The results of the effectiveness of the evluted insecticides suggest tht the chemicl control of thrips on citrus should be done between the second nd third week fter mssive petl fll. The flowering nd fruit-let durtion vry yer by yer nd depend exclusively on wether conditions. Since resistnce to insecticides (chlorpyrifos) hs been reported (Purvis 2002) ll insecticides tht were found to be effective ginst KCT popultions should be rotted in the context of n IPM progrmme in order to minimise the risk of resistnce development. Botnicl nd biologicl substnces will continue to ply mjor role in field trils nd their evlution for effectiveness will be further studied. In this context we re iming to find biologicl gents nd substnces tht will be effective under Cyprus conditions, protecting thus, the environment nd public helth from the unfvourble consequences from the use of toxic synthetic ctive ingredients. ACKNOWLEDGEMENTS The Achelei s Experimentl Sttion nd the Plnt Protection Section s stff is cknowledged for their ssistnce in conducting this study. REFERENCES Bgnll RS (1916) Brief descriptions of new Thysnopter VII. 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