Research Article Control of Trialeurodes vaporariorum

Transcription

1 Ž. LAZNIK, D. ŽNIDARČIČ, S. TRDAN Reserch Article Turk J Agric For 35 () TÜBİTAK doi:.396/tr-7- Control of Trileurodes vporriorum (Westwood) dults on glsshouse-grown cucumers in four different growth sustrtes: n efficcy comprison of folir ppliction of Steinernem feltie (Filipjev) nd sprying with thimethoxmn Žig LAZNIK, Drgn ŽNIDARČIČ, Stnislv TRDAN* University of Ljuljn, Biotechnicl Fculty, Deprtment of Agronomy, Jmnikrjev, SI- Ljuljn - SLOVENIA Received:.7. Astrct: In glsshouse experiment, the effectiveness of the entomopthogenic nemtode (EPN) Steinernem feltie (Filipjev) (Rhditid: Steinernemtide) ws compred with thimethoxm for the control of dults of the greenhouse whitefly (GWF), Trileurodes vporriorum (Westwood) (Homopter: Aleyrodide), on slicer cucumers. In period from mid June to the end of August (7 nd 8), cucumers were grown in 4 different growth sustrtes: expnded perlite, expnded vermiculite, light expnded cly, nd pet. A suspension of the nemtode (5 infective juveniles ml - ) ws pplied to cucumers 5 times in 7 nd twice in 8, whilst n insecticide thimetoxm t the recommended dose (.7 g L - ) ws used 3 times in 7 nd twice in 8. Adults of GWF showed sensitivity to the ttck of S. feltie, nd lso showed sensitivity to the ppliction of the thimethoxm. Different control strtegies hd greter influence on the men mss of cucumers thn the type of growth sustrte. In the control tretment, where we found the highest numer of GWF dults in oth yers, the men mss of cucumers ws the lowest. In 7, the men numer of GWF dults per lef ws significntly the lowest in tretment with thimetoxm, while in 8 there were no differences etween the influence of thimethoxm nd EPNs. Light expnded cly ggregte ppered to e less pproprite growth sustrte, s cucumers grown on this type of sustrte produced the lowest numer of fruits per plnt. Key words: Biologicl control, cucumers, entomopthogenic nemtodes, greenhouse, insecticide, greenhouse whitefly Introduction The greenhouse whitefly (GWF), Trileurodes vporriorum (Westwood) (Homopter: Aleyrodide), is n importnt polyphgous pest of vrious crops (Vet et l. 98; Johnson et l. 99). Adults nd lrve cuse dmge to plnts y sucking the phloem sp, encourging the growth of sooty molds on leves, nd trnsmitting some * E-mil: stnislv.trdn@f.uni-lj.si plnt viruses (Coffin nd Coutts 995; Guzmn et l. 997). In northern climtes, this whitefly usully lives in glsshouses on wild plnts, or in summer on djcent plnts outside. Further south, dults my lso overwinter on wild plnts growing outdoors if the climtic conditions re not too severe. The development period from egg to dult requires out 5-3 dys t C, nd -5 dys t 4 C. GWF 63

2 Control of Trileurodes vporriorum (Westwood) dults on glsshouse-grown cucumers in four different growth sustrtes: n efficcy comprison of folir ppliction of Steinernem feltie (Filipjev) nd sprying with thimethoxm cn live for months, nd oviposition time cn exceed the development time of immtures, resulting in overlping genertions. Optiml reltive humidity is out 75%-8%, nd the developmentl threshold for ll stges is out 8.5 C (Cpiner ). It is well known tht the greenhouse whitefly hs strong preference for cucumers grown in greenhouses (Jeon et l. 9). The extensive use of pesticides ginst potentil pests hs resulted in the ppernce of pesticide resistnce in mny glsshouse pests (Yorulmz nd Ay 9), including T. vporriorum (Gormn et l. ), nd phytotoxicity nd pesticide residue prolems on vegetles (Quinln 988). The demnd for reduction in pesticide use nd the requirement for residue-free food hve resulted in n incresing interest in iologicl control systems for use in glsshouses. Thimethoxm is chloronicotinyl insecticide nd is widely used to control homoptern pests (Elert et l. 998), nd hs een shown to hve high efficcy ginst GWF (Bi et l. ). Entomopthogenic nemtodes (EPNs) crry species-specific symiotic cteri which, fter nemtodes infect their insect hosts, re relesed into the hemolymph of the host. Only infective juveniles (IJs) re le to infect the insect host (Ky 99). Severl ttempts hve een mde to use EPNs s iocontrol gents ginst trget pests locted on the crop folige ut erly results were not encourging in glsshouses (Hr et l. 993) or fields (Ky et l. 98; Hr et l. 993; Grewl nd Georgis 998; Susurluk nd Ehlers 8). However, recent development of more effective ppliction techniques/tools for nemtodes promises to improve the efficcy of nemtodes ginst folir pests (Lznik et l. ), prticulrly under glsshouse conditions (Trdn et l. 7). The use of growth sustrtes is n incresingly importnt method for cucumer production in glsshouses (Prks et l. 4). The dvntge of this type of production in comprison with conventionl (soil) production is tht, eside controlled nutrient supply, there is lso replcement of inpproprite sustrte, prticulrly in cses where pest orgnisms occur nturlly in the sustrte (Schnitzler 5). The usge of EPNs in these kinds of production systems cn e through folir ppliction, which provides rpid ctivity of these iologicl gents (Trdn et l. 7). Previous reserch on folir ppliction of Steinernem feltie (Filipjev) (Rhditid: Steinernemtide) suspension showed its high efficcy in controlling Colordo potto eetle (Leptinotrs decemlinet [Sy]) (Lznik et l. ), lrve of sweetpotto whitefly (Bemisi tci [Genndius]) (Cutherston et l. 3), nd western flower thrips (Frnkliniell occidentlis [Pergnde]) (Trdn et l. 7). We imed to study the efficcy of numerous pplictions of this species ginst dults of GWF on glsshouse-grown cucumers, nd to compre the results with the efficcy of the insecticide thimethoxm. We lso imed to see if the numer of GWF dults is negtively correlted with the yield of the cucumers, s ws documented in one relted rticle (Johnson et l. 99), where the reserchers discovered this correltion with GWF immture stges nd tomto yield. Mterils nd methods Study site nd mteril In 7 nd 8, greenhouse experiment ws conducted t the experimentl field of the Biotechnicl Fculty in Ljuljn (46 4ʹN ltitude, 4 3ʹE longitude, 99 m ove the se level), Sloveni. The study ws conducted in greenhouse where mssive occurrence of greenhouse whitefly on different hosts (cucumer, eggplnt, tomto, en) hd een recorded in the previous yers. Seeds of the slicer cucumer, cv. Jzzer F, were sown in 9 seedling trys filled with fertilized pet. After seedling emergence, the trnsplnts were overhed irrigted s needed. When they reched 3 fully expnded leves, the seedlings were fertigted weekly with 5 mg L - of solule fertilizer (5N-5P O 5-5K O). After the nursery period, the trnsplnts were trnsferred to the high-roof pssiveventilted greenhouse (width 8 m, length 4 m, est-west orienttion) on June. Plnts were set into m long y.4 m wide y.3 m tll lck plstic sleeves (plots), nd then plced.8 m prt in rows to give popultion of 4 plnts m -. To llow dringe, holes out.5 cm in dimeter were drilled out 5 cm from the ottom of the continers. 63

3 Ž. LAZNIK, D. ŽNIDARČIČ, S. TRDAN The sleeves were filled with of 4 different growth sustrtes: expnded perlite (ulk density: 6 kg m -3 ), expnded vermiculite (medium grnultion, ph 7.4), light expnded cly ggregte (grin size 8-6 mm), nd pet (Humin sustrte N Neuhus). All plnts were fertigted with the sme (drip irrigtion) system nd sme rte of nutrients, which consisted of solule fertilizer, clcium nitrte, nd mgnesium sulfte. The mount of dded wter next to fertigtion (there ws no irrigtion) ws dependent on moisture of sustrte, which ws mesured y tensiometer. The city wter source showed ph of 6.8 nd so ws djusted to 7. with nitric cid. A trellis system nd high tensile fencing wire ws used to support the cucumers to height of 3 m. Greenhouse experiment In 7 nd 8 the glsshouse temperture t the time of the experiment ws C (8- ) nd C (-7), while the reltive humidity ws 7.5%-68.% (8-) nd 55.%-9.% (-7). Four plnts in ech sleeve (su-plot) were spryed with suspension of S. feltie (the iopreprtion Entonem, mnufcturer: Koppert B.V., Berkel en Rodenrijs, the Netherlnds; supplier: Zeleni hit d.o.o., Ljuljn, Sloveni). A stndrd rte of 5 infective juveniles (IJs) S. feltie per ml of wter ws used. Four plnts were spryed with thimethoxm (.7 g L - ;.7% Actr 5 WG; mnufcturer: Syngent; supplier: Syngent Agro d.o.o., Ljuljn, Sloveni), nd the 4 control plnts were spryed with wter. Before sprying ech suspension of nemtodes,.5% of the surfctnt Nu- Film-7 (.i. di--p-methene, 96%; mnufcturer: Lnces Links SA, Genev, Switzerlnd; supplier: Krsi Dutovlje d.o.o., Ljuljn, Sloveni) ws dded to the spryer to enle the suspension to move more effectively cross the lef surfce nd enhnce GWF loction. In 7, the first ppliction of the iologicl gents (efore ppliction the viility of the nemtodes ws checked) nd insecticide ( June) occurred when the first GWF dults were oserved on the leves of cucumers. Weekly pplictions therefter (,, 3, 4, nd 5 weeks fter the first ppliction [AFA]) of S. feltie suspension (t glsshouse temperture) were mde y n injector hollow cone nozzle TVI 8 ttched to motor-operted ckpck spryer. Sprys with thimethoxm ( June, 3 nd 5 AFA) were pplied t the sme time of the dy (erly evening) using ckpck spryer with n injector nozzle ID 9. The output liquid pressure in oth cses ws. MP, nd the flow rte ws etween.4 nd.46 L min -. The droplet size fter the ppliction of EPNs suspension ws 4 μm, while fter the ppliction of thimetoxm the sme prmeter ws 3 μm. In 8, the first ppliction of the EPNs nd the insecticide ws performed ( July). Weekly ppliction (, weeks AFA) of the nemtodes ws performed with the sme equipment s in 7, similr to the ppliction of the insecticide weeks AFA. Lter occurrence of GWF dults in 8 ws the min reson for reducing nemtode ppliction in 8 compring with 7. After ppliction of EPN, the confirmtion tht GWF dults were killed y the nemtodes ws done y collecting ded dults on the surfce of cucumer leves. They were put into petri dishes in the drk (room conditions). The presence of the new popultion of S. feltie in the ody of GWT dults nd in their vicinity ws used s confirmtion tht the dults hd ctully een killed y nemtodes (Trdn et l. 8). No pests, other thn the GWF studied here, were seen on the cucumers to ny sustntil degree during the course of study. The only other infection of note on cucumers ws powdery mildew Spherothec fuligine (Schlecht.) Pollcci, which ws controlled efficiently in the erly stges of infection with sprying twice ( nd 3 weeks AFA) with the fungicide zoxystroin (5 g L - ;.75% Qudris; mnufcturer: Syngent Limited AG, Fernhurst, UK; supplier: Syngent Agro d.o.o., Ljuljn, Sloveni). In oth yers the fungicide ws pplied to ll experimentl res. Oservtions nd evlutions Evlutions were tken t 3 time-points in 7 (3, 5, nd 7 weeks AFA) nd time-points in 8 ( nd weeks AFA) during the growing seson. At ech time-point, 3 rndomly selected plnts of out the sme height in ech su-plot were ssessed for the numer of GWF dults. Three leves (lower, middle, nd upper prt) from ech chosen plnt were evluted in the morning (t out 7), when dults were stle due to reltively low temperture 633

4 Control of Trileurodes vporriorum (Westwood) dults on glsshouse-grown cucumers in four different growth sustrtes: n efficcy comprison of folir ppliction of Steinernem feltie (Filipjev) nd sprying with thimethoxm (Bellows et l. 988). Cucumer fruits were hrvested when their dimeters were 3-4 cm. In 7 hrvesting egn 3 weeks fter the first ppliction nd continued up to 5 weeks fter the first ppliction, when ll remining mrketle fruit ws hrvested. The yield ws clssified into 3 groups ccording to hrvest time (up to 3 weeks AFA, etween 3 nd 5 weeks AFA, nd 5 weeks AFA). In 8 hrvesting egn week AFA nd continued up to weeks AFA, when ll remining mrketle fruit ws hrvested. The yield ws clssified into groups ccording to hrvest time (up to week AFA nd weeks AFA). The cucumer yield ws determined in wys: ) mss of fruits per plnt, nd ) numer of fruits per plnt (Trdn et l. 7). Dt nlyses Differences in numer of fruits, nd mss of fruits with 3 different pest tretments (EPN, insecticide, nd control) nd etween 4 different growth sustrtes were nlyzed individully t ech time of fruit picking using ANOVA. Prior to nlysis, ech vrile ws tested for homogeneity of vrince, nd those dt found to e non-homogeneous were trnsformed to log(y) efore ANOVA. Significnt differences (P.5) etween men vlues were identified using Student-Newmn-Keuls s multiple rnge test. Dt of the numer of GWF dults on the cucumer leves hd nonprmetric distriution nd so were nlyzed using the Kruskl-Wllis test. As in the cse of the first prmeters, mens were determined to e significntly different when there ws no overlp of the 95% confidence intervls. All sttisticl nlyses were done using Sttgrphics Plus for Windows 4. (Sttisticl Grphics Corp., Mnugistics, Inc.). The dt re presented s untrnsformted mens ± SE. Results Numer of GWF on cucumers In oth yers the dte of ssessment (7: F = 86.6, df =, 79, P <.; 8: F = 5.59, df =, 7, P <.), type of the sustrte (7: F = 4.37, df = 3, 79, P <.; 8: F =.7, df = 3, 7, P <.44), control method (7: F = 34.7, df =, 79, P <.; 8: F =.9, df =, 7, P <.), nd interction etween type of sustrte nd control method (7: F = 6.4, df = 6, 79, P <.; 8: F =.35, df = 6, 7, P =.396) hd significnt influence on the men numer of T. vporriorum dults per lef. Significntly, the lowest numer of the GWF dults per lef in 7 (3 weeks AFA: 3. ±.47 [F = 7., df = 3, 59, P <.]; 5 weeks AFA: 5.89 ± 4.4 [F = 5.3, df = 3, 59, P <.), nd in 8 ( week AFA: ± 3.4 [F =.4, df = 3, 4, P =.]; weeks AFA: 3. ± 4. [F =.99, df = 3, 4, P =.4]) ws confirmed on the cucumers grown in expnded perlite (Figure, ). Additionlly in 8, the numer of the GWF dults in this tretment did not differ significntly with the tretments vermiculite ( week AFA: ±.66; weeks AFA: ± 8.) nd light expnded cly ggregte (43.56 ±.4). In 7 nd 8, there were lso no significnt differences on the men numer of the GWF dults etween vermiculite nd light expnded cly ggregte t the sme week AFA (7: from 4. ±.48 [3 weeks AFA - vermiculite] to ± 8.8 [7 weeks AFA - light expnded cly ggregte]; 8: from ±.66 [ week AFA - vermiculite] to 9. ± 43.3 [ weeks AFA - light expnded cly ggregte]). The highest men numer of T. vporriorum dults per lef ws in 7 confirmed t pet nd the vlues rnged from 3.6 ± 7.7 (3 weeks AFA) to ± 5.83 (5 weeks AFA). The men numer of GWF dults per lef ws significntly influenced with the control methods. In oth yers, significntly, the highest men numer of the T. vporriorum dults per lef ws confirmed t the control tretment nd vlues rnged from.3 ± 5.83 (3 weeks AFA) to 9.7 ±.77 (7 weeks AFA) in 7, nd from 89. ±.6 ( week AFA) to 8.5 ± 33. ( weeks AFA) in 8 (Figure c, d). In 8, there were no significnt differences etween the influence of thimethoxm nd EPNs, while yer efore the men numer of GWF dults ws significntly the lowest in tretment with thimetoxm 3 (.58 ±.38) nd 7 weeks (5.64 ± 5.7) AFA. Mss of cucumers In oth yers, only the control method (7: F =.75, df =, 34, P <.; 8: F = 39.8, df =, 33, P <.) hd significnt influence on the 634

5 Ž. LAZNIK, D. ŽNIDARČIČ, S. TRDAN 6 EP Vermiculite LECA Pet 6 EP Vermiculite LECA Pet 4 ) 4 ) B ca A A B B C Men numer of GWF 6 4 c) Untrete d Thimeth oxm EPNs 6 4 d) Untreted Thimeth oxm EPNs ca B C 6 4 A Figure. Men numer of GWF dults per plnt in 7 (, c) nd 8 (, d) t different growth sustrtes (, ) (EP - expnded perlite, LECA - light expnded cly ggregte) nd control methods (c, d). Different smll letters indicte significnt differences (P >.5) within AFA (fter first ppliction) nd different cpitl letters indicte significnt differences etween growth sustrtes nd control method ccording to Student-Newmn-Keuls s multiple rnge test. mss of cucumers per plnt. In 7, the type of sustrte hd no significnt influence on the yield (g) of cucumers etween 3 nd 5 weeks AFA (F =.9; df = 3, ; P =.9647) nd the vlues rnged from ± 7.73 [expnded perlite] to 94.5 ± 5.36 [vermiculite]), nd etween 5 nd 7 weeks AFA (F =.7; df = 3, ; P =.3676), when the vlues rnged from 8.86 ±.58 [vermiculite] to 3. ± 34.9 [pet] (Figure ). In 7 nd 8, the lowest men mss (g) of fruits per plnt ws recorded 3 weeks AFA (7.6 ±.75) nd week AFA (37.6 ± 9.47) on cucumers grown on expnded perlite, respectively). In 8, the highest men mss (g) of cucumers per plnt ws recorded on vermiculite week AFA (95.56 ± 8.75); however, etween vermiculite nd light expnded cly ggregte in oth tken timepoints there were no significnt differences (Figure ). The lowest men mss (g) of cucumers per plnt ws confirmed t the control tretment nd the vlues rnged from 9.9 ±.9 (3 weeks AFA) to ±.83 (etween 3 to 5 AFA) in 7 nd from.5 ± 6.46 ( weeks AFA) to 8.48 ± 9.47 ( week AFA) in 8 (Figure c, d). In 8, there were no significnt differences (F = 39.8, df =, 33, P <.) etween thimethoxm nd EPNs 635

6 Control of Trileurodes vporriorum (Westwood) dults on glsshouse-grown cucumers in four different growth sustrtes: n efficcy comprison of folir ppliction of Steinernem feltie (Filipjev) nd sprying with thimethoxm EP Vermiculite LECA P et ) B B A A EP Vermiculite LECA Pet c ) c Men mss of cucumers (g) c) Untreted Thimethoxm EPNs A Untreted Thimethoxm EPNs B B d) A A Figure. Men mss of cucumers per plnt (g) in 7 (, ) nd 8 (c, d) t different growth sustrtes (, ) (EP - expnded perlite, LECA - light expnded cly ggregte) nd control methods (c, d). Different smll letters indicte significnt differences (P >.5) within AFA (fter first ppliction) nd different cpitl letters indicte significnt differences etween growth sustrtes nd control method ccording to Student-Newmn-Keuls s multiple rnge test. tretment nd the vlues rnged from 88. ±.3 (EPNs) to 3.69 ±.7 (thimethoxm). In 7, (F =.46, df =, 34, P =.87) the highest men mss (g) of cucumers ws recorded 7 weeks AFA with EPNs tretment (34.59 ±.38). Men numer of cucumers In oth yers, only the type of sustrte (7: F = 3.7, df = 3, 65, P =.99; 8: F = 3.64, df = 3, 8, P =.6) hd significnt influence on the men numer of cucumers per plnt. In 7, the type of sustrte hd no significnt influence on the men numer of cucumer fruits etween 3 nd 5 weeks AFA (F =.874; df = 3, ; P =.9647), nd the vlues rnged from.9 ±.36 (light expnded cly ggregte) to.89 ±.54 (vermiculite) (Figure 3). In the sme yer 3 weeks AFA (.83 ±.4) nd 5 weeks AFA (.86 ±.34), the lowest men numer of cucumer fruits ws lso confirmed on the light expnded cly ggregte, which ws lso the cse in 8 ( week AFA:.63 ±.4; weeks AFA:.67 ±.9). In the first week AFA in 8, the men numer of cucumers per plnt did not significntly differ (F = 3.64, df = 3, 8, P =.6) etween expnded perlite, vermiculite, nd pet (Figure 3). The vlues rnged from 3.8 ±.35 (thimethoxm, week AFA) to 3.67 ±.6 (EPNs, weeks AFA). In 7, the control tretment influenced the numer of cucumers per plnt nd the vlues rnged from 636

7 Ž. LAZNIK, D. ŽNIDARČIČ, S. TRDAN 8 EP Vermiculite LECA Pet 8 EP Vermiculite LECA P et 7 ) 7 ) Men numer of cucumers fruits per plnt C c) C B Untret ed Thi me thoxm EP Ns d) Untre te d Thimethoxm EPNs B C B B Figure 3. Men numer of cucumers fruits per plnt in 7 (, ) nd 8 (c, d) t different growth sustrtes (, ) (EP - expnded perlite, LECA - light expnded cly ggregte) nd control methods (c, d). Different smll letters indicte significnt differences (P >.5) within AFA (fter first ppliction) nd different cpitl letters indicte significnt differences etween growth sustrtes nd control method ccording to Student- Newmn-Keuls s multiple rnge test..88 ±.35 (untreted, 7 weeks AFA) to 4. ±.4 (EPNs, 3 weeks AFA) (Figure 3c). For 3 (F =.9, df =, 6, P =.56) nd 7 weeks (F =.84, df =, 6, P =.45) AFA, the plnts treted with EPNs (4. ±.4, nd.7 ±.3) nd thimetoxm (3.75 ±.45, nd.5 ±.7) gve significntly the highest numer of fruits per plnt, while 5 weeks AFA significntly (F =.9, df =, 6, P =.76) the highest yield (3.5 ±.4) ws chieved with the use of thimetoxm. In 8, different control methods did not hve n influence on the men numer of cucumers fruits per plnt (Figure 3d). Discussion In the present study, dults of GWF showed sensitivity to the ttck of the S. feltie nd to insecticide thimethoxm under glsshouse conditions. We ttriute these results to our multifold ppliction of nemtodes, since it is known tht, in generl, the survivl of the infective juveniles on the lef decresed with the exposure time (Jin et l., 4). In similr study, higher concentrtion of EPNs ws lso seen to produce greter mortlity rte of western flower thrips (Ess et l. 4). 637

8 Control of Trileurodes vporriorum (Westwood) dults on glsshouse-grown cucumers in four different growth sustrtes: n efficcy comprison of folir ppliction of Steinernem feltie (Filipjev) nd sprying with thimethoxm Qui et l. (8) evluted the potentil for using infective juveniles of the Steinernem feltie to control the sweetpotto whitefly Bemisi tci B iotype on cucumer, hiiscus, nd collrd, under greenhouse conditions. The mortlity of B. tci nymphs incresed y % on cucumer plnts when S. feltie concentrtion incresed from 5 to 5, infective juveniles ml -. In relted reserch y Cuthertson et l. (3), the comptiility of S. feltie with different chemicl insecticides ginst the sweetpotto whitefly, Bemisi tci (Homopter: Aleyrodide), ws investigted. The uthors concluded tht nemtodes in comintion with imidcloprid gve significntly higher mortlity of B. tci lrve. Desirle ssets such s ese of mss production nd efficcy nd sfety to nontrget orgnisms hve evoked commercil interest in EPNs (Prwinder nd Georgis 994). From prxis-orientted point of view, high doses proly negtively ffect the prcticl ppliction of EPN formultions, due to cost nd formultion stility (Athnssiou et l. ; Lznik et l. ). However, other studies show tht, for some species, lower doses re required (Rmos-Rodríguez et l. 6). Thimethoxm is chloronicotinyl insecticide tht cts s nicotin cetylcholine receptor gonist nd is widely used to control homoptern pests (Leicht 993; Elert et l. 998). In relted reserch (Bi et l. ), it is reported tht it cused only 67% mortlity of GWF nymphs. Elert et l. (998) however suggested tht imidcloprid cn control whiteflies resistnt to conventionl insecticides nd soil tretments hve no dverse effects on eneficil orgnisms, nd so it fits well into resistnt mngement strtegies nd cn e considered n importnt component of integrted whitefly mngement. We lso determined the effect of the feeding of GWF dults on men mss of cucumers. Different control strtegies hd greter influence on the men mss of cucumers thn type of the growth sustrte. In the control tretment, where we found the highest numer of GWF dults, the men mss of cucumers in oth oserved yers ws the lowest. Results from 7 even proved tht the yield, where the control strtegy ws performed with the use of EPNs, ws the gretest. In some relted reserch (Johnson et l. 99), the uthors concluded tht the feeding of the immture GWF hd gret influence on the tomto yield, which ws lso determined in study y Trdn et l. (7). The type of the growth sustrte did not hve significnt influence on the men mss of the cucumers in 7, ut in 8 we confirmed the highest men mss of cucumers on plnts, grown in vermiculite, where the lowest numer of the GWF dults ws lso found. In similr study (Szwejd nd Nwrock 999), the tomto lefminer (Liriomyz ryonie) cused significntly greter dmge to tomto plnts grown on pet. It is prole tht the type of growth sustrte ffected the susceptiility of tomto plnts, s oth tomto nd cucumer re eqully susceptile to lefminers (Tokumru nd Ae 5). In our experiment, light expnded cly ggregte ppered to e less pproprite growth sustrte, s cucumers grown on this type of sustrte produced the lowest numer of fruits per plnt. Similr conclusions re lso reported y Trdn et l. (7) in reserch regrding the control of western flower thrips on cucumers. In similr reserch with different growth sustrtes (coir, swdust, rockwool, perlite, nd cucumer mix), no differences in the numer of fruits per plnt nd verge fruit mss were oserved (Prks et l. 4). Similr conclusions were lso reched in study exploring the influences of medium perlite, corse perlite, nd pine rk on cucumer yield (Cntliffe et l. 3). Although it is difficult to compre results cross studies, it ppers s though there is generlly not lrge influence of sustrte type on the numer or mss of cucumer fruits. However, our results indicte tht, in conditions similr to those of our study, the use of light expnded cly ggregte is not dvisle, s it ws seen to produce poorer growth results. Our dt indicted tht oth vermiculite nd pet re suitle for cucumer production, s previously demonstrted (Swn et l. 999; Trdn et l. 7). Chemicl control is still n importnt component of integrted pest mngement systems (Gnesn et l. 7). GWF hve lredy developed resistnce to some conventionl insecticides s cephte nd dicrotophos in Cliforni (Omer et l. 99). Introducing nd lternting these chemicls on cucumers in defined wy will e strtegic to comt the potentil risk of GWF resistnce to these insecticides. On the other hnd, the results 638

9 Ž. LAZNIK, D. ŽNIDARČIČ, S. TRDAN of some reserch recommended the use of the sustnces of non-insecticidl origin for exmple the household sops nd detergents ginst GWF dults in glsshouse conditions (Aris et l. 6). Furthermore, for the control of GWF on cucumer crops, iologicl control with EPN suspension ws seen to e eqully s effective s the currently widelyused nd highly-recommended chemicl insecticide thimethoxm. Thus, we think tht, with proper optimiztion, the ppliction of these iologicl gents represents very promising lterntive to the current chemicl control methods. Acknowledgements This work ws done within Horticulture No P4-3-48, progrm funded y the Slovenin Reserch Agency. Prt of the reserch ws funded within professionl tsks from the field of plnt protection, the progrm funded y the Ministry of Agriculture, Forestry nd Food of the Repulic of Sloveni - Phytosnitry Administrtion of the Repulic of Sloveni. We thnk the nonymous reviewers for comments tht hve improved the qulity of the pper. References Aris C, Silv G, Tpi M, Hepp R (6) Assessment of household sops nd detergents to control Trileurodes vporriorum (Westwood) in the greenhouse. Agro-Cienci : 7-4. Athnssiou CG, Kvlliertos NG, Menti H, Krnstsi E () Mortlity of four stored product pests in stored whet when exposed to doses of three entomopthogenic nemtodes. J Econ Entomol 3: Bellows TS Jr, Perring TM, Arkw K, Frrr CA (988) Ptterns in diel flight ctivity of Bemisi tci (Homopter: Aleyrodide) in cropping systems in southern Cliforni. Environ Entomol 7: 5-8. Bi JL, Toscno NC, Bllmer GR () Greenhouse nd field evlution of six novel insecticides ginst the greenhouse whitefly Trileurodes vporriorum on strwerries. Crop Prot : Cntliffe DJ, Funes J, Jovicich E, Prnjpe A, Rodriguez J, Shw N (3) Medi nd continers for greenhouse soilless grown cucumers, melons, peppers nd strwerries. Act Hortic 64: Cpiner JL () Order Homopter phids, lef- nd plnthoppers, psyllids nd whiteflies. In: Hndook of Vegetle Pests. Acdemic Press, Sn Diego et l.: pp Coffin RS, Coutts RHA (995) Reltionships mong Trileurodes vporriorum-trnsmitted yellowing viruses from Europe to North Americ. J Phytopthol 43: Cuthertson AGS, Hed J, Wlters KFA, Murry AWA (3) The integrted use of chemicl insecticides nd the entomopthogenic nemtode, Steinernem feltie, for the control of sweetpotto whitefly, Bemisi tci. Nemtology 5: Ess L, Borgemeister C, Poehling HM (4) Effectiveness of different species/strins of entomopthogenic nemtodes for control of western flower thrips (Frnkliniell occidentlis) t vrious concentrtions, host densities, nd tempertures. Biol Control 9: Elert A, Nuen R, Leicht W (998) Imidcloprid, novel chloronicotinyl insecticide: iologicl ctivity nd griculturl importnce. In: Insecticides with Novel Modes of Action- Mechnism nd Appliction, (Eds. I Ishy, D Degheele) Springer, Berlin, Heidelerg: pp Gnesn S, Gnesh Kuppusmy R, Sekr R (7) Integrted mngement of stem rot disese (Sclerotium rolfsii) of groundnut (Archis hypoge L.) using Rhizoium nd Trichoderm hrzinum (ITCC - 457) Turk J Agric For 3: 3-8. Gormn K, Hewitt F, Denholm I, Devine GJ () New developments in insecticide resistnce in the glsshouse whitefly (Trileurodes vporriorum) nd the two-spotted spider mite (Tetrnychus urtice) in the UK. Pest Mng Sci 58: 3-3. Grewl PS, Georgis R (998) Entomopthogenic nemtodes. In: Biopesticides: Use nd Delivery, (Eds. FR Hll nd JJ Menn). Humn Press, Totow, New Jersey, pp Guzmn P, Arredondo CR, Emmtty D, Gilertson RL (997) Prtil chrcteriztion of two whitefly-trnsmitted geminiviruses infecting tomtoes in Venezuel. Plnt Dis 8: 3. Hr AH, Ky HK, Gugler R, Leeck LM, Mello CL (993) Entomopthogenic nemtodes for iologicl control of lefminer, Liriomyz trifolii (Dipter: Agromyzide). Entomophg 38: Jeon HY, Kim HH, Yng CY, Kng TJ, Kim DS (9) A tenttive economic injury level for greenhouse whitefly on cucumer plnts in the protective cultivtion. Koren J Hortic Sci Technol 7: Jin YL, Hn RC, Cong B (4) Effects of ppliction prmeters nd djuvnts on the folir survivl nd persistence of entomopthogenic nemtode Steinernem crpocpse ll strin on cges. Entomol Sin : 99-. Johnson MW, Cprio LC, Coughlin JA, Tshnik BE, Rosenheim JA, Wel Ter SC (99) Effect of Trileurodes vporriorum (Homopter: Aleyrodide) on Yield of Fresh Mrket Tomtoes. J Econ Entomol 85:

10 Control of Trileurodes vporriorum (Westwood) dults on glsshouse-grown cucumers in four different growth sustrtes: n efficcy comprison of folir ppliction of Steinernem feltie (Filipjev) nd sprying with thimethoxm Ky HK, Hr AH, Rerdon RC (98) Lortory nd field evlution of Neoplectn crpocpse (Rhditid: Steinernemtide) ginst the elm lef eetle (Coleopter: Chrysomelide) nd the western spruce udworm (Lepidopter: Torticide). Cn Entomol 3: 787. Ky HK (99) Soil ecology. In: Entomopthogenic Nemtodes in Biologicl Control, (Eds. R Gugler, HK Ky), CRC Press, Boc Rton, FL, USA, pp Lznik Ž, Tóth T, Lktos T, Vidrih M, Trdn S () Control of the Colordo potto eetle (Leptinotrs decemlinet [Sy]) on potto under field conditions: comprison of the efficcy of folir ppliction of two strins of Steinernem feltie (Filipjev) nd sprying with thimetoxm. J Plnt Dis Prot 7: Leicht W (993) Imidcloprid - chloronicotinyl insecticide. Pestic Outlook 4: 7-. Omer AD, Leigh TF, Grnett J (99) Insecticide resistnce in field popultion of greenhouse whitefly (Homopter: Aleyrodide) in the Sn Joquin vlley (Cliforni) cotton system. J Econ Entomol 85: -7. Prks S, Newmn S, Golding J (4) Sustrte effects on greenhouse cucumer growth nd fruit qulity in Austrli. Act Hortic 648: Prwinder G, Georgis R (994) Fundmentl reserch on entomopthogenic nemtodes: An industril perspective. Proceed. XXVII th Annul Meet. Soc. Invert. Pthol. vol. : pp Quinln RJ (988) Use of fungi to control insects in greenhouses. In: Fungi in Biologicl Control Systems (Ed. MN Burge). Mnchester University Press, Mnchester, UK, pp Qiu BL, Mndour NS, Xu CX, Ren SX (8) Evlution of the entomopthogenic nemtode Steinernem feltie s iologicl control gent of the whitefly, Bemisi tci. Int J Pest Mng 54: Rmos-Rodríguez O, Cmpell JF, Rmswmy SB (6) Pthogenity of three species of entomopthogenic nemtodes to some mjor stored-products insect pests. J Stored Prod Res 4: 4-5. Swn OM, Eiss AM, Aou-Hdid AF (999) The effect of different growing medi on cucumer seedling production, fruit yield nd qulity under greenhouse conditions. Act Hortic 49: Schnitzler WH (5) Pest nd disese mngement of soilles culture (Review n.). Itlus Hortus : 33-4 [Itlin]. Susurluk A, Ehlers R-U (8) Field persistence of the entomopthogenic nemtode Heterorhditis cteriophor in different crops. BioControl 53: Swejzd J, Nwrock B (999) Hrmfulness of Liriomyz ryonie (Dipt: Agromyzide) on tomto nd cucumer cultivted in soil-less sustrtes. Progress Plnt Prot 39: [Polish]. Tokumru S, Ae Y (5) Effects of host plnts on the development nd host preference of Liriomyz stive, L. trifolii nd L. ryonie (Dipter: Agromyzide). Jpn J Appl Entomol Zool 49: Trdn S, Žnidrčič D, Vidrih M (7) Control of Frnkliniell occidentlis on glsshouse-grown cucumers: n efficcy comprison of folir ppliction of Steinernem feltie nd sprying with mectin. Russ J Nemtol 5: Trdn S, Vidrih M, Vlič N, Lznik Ž (8) Impct of entomopthogenic nemtodes on dults of Phyllotret spp. (Coleopter: Chrysomelide) under lortory conditions. Act Agric Scnd Sect B - Soil Plnt Sci 58: Vet L, vn Lenteren JV, Woets J (98) The prsite-host reltionship etween Encrsi formos nd Trileurodes vporriorum IX. A review of the iologicl control of the greenhouse whitefly with suggestion for future reserch. Z Angew Entomol 9: 6-5. Yorulmz S, Ay R (9) Multiple resistnce, detoxifying enzyme ctivity, nd inheritnce of mectin resistnce in Tetrnychus urtice Koch (Acrin: Tetrnychide). Turk J Agric For 33: