Abstract. Annkathrin Gronle*,**, Herwart Böhm* and Jürgen Heß**

Transcription

1 A. Gronle, H. Böhm, J. Heß Lnuforsh Appl Agri Forestry Res (64)31-44 DOI: /LBF_2014_ Effet of interropping winter pes of iffering lef type n time of flowering on nnul wee infesttion in eep n shllow ploughe soils n on pe pests Annkthrin Gronle,, Herwrt Böhm n Jürgen Heß Astrt The performne of orgni pe proution lrgely epens on preventive n ulturl ontrol strtegies for wees n pests. Fiel experiments were rrie out to stuy the effet of interropping norml-lefe (v. E.F.B. 33) or semi-lefless, erly-flowering winter pe (v. Jmes) n tritile on the infesttion with nnul wees, pe phis n moths in omprison to the respetive sole rops. Also, shllow ploughing (10 to 12 m) vs. eep ploughing (25 to 27 m) ws investigte with regr to n infesttion with nnul wees. The higher wee suppressive ility of norml-lefe winter pe v. E.F.B. 33 ompre with semi-lefless v. Jmes ws ue to lower light trnsmission to the wee nopy level. In ontrst to E.F.B. 33, interropping Jmes signifintly reue the wee infesttion ompre to the respetive sole rop. The ploughing system h no signifint effet on the wee infesttion in rops iffering in their ility to suppress nnul wees. Sole rops were foun to hve higher pe phi ensity, iniene n umultive phi-ys thn the orresponing interrops. Interropping winter pes n tritile, however, ws not enefiil in reuing n infesttion with pe moths. Keywors: orgni frming, ploughing system, wee suppression, Ayrthosiphon pisum Hrris, umultive phi-ys, Cyi nigrin Friius Zusmmenfssung Einfluss es Mishfruhtnus von Winterersen mit untershielihen Bltttypen un Blütezeitpunkten uf s nnuelle Unkrutufkommen in tief- un flhwenen ereiteten Böen un uf Ersen-Shälinge Die Leistungsfähigkeit es ökologishen Ersennus hängt in hohem Mße von voreugenen Kontrollstrtegien für Unkräuter un Shälinge. Untersuht wure er Einfluss es Reinst- un es Mishfruhtnus einer normllättrigen (E.F.B. 33) un einer hllttlosen, frühlühenen Winterersen-Sorte (Jmes) mit Tritile uf s nnuelle Unkrutufkommen sowie en Befll mit Ersenlttlus un -wikler. Zuem wure eine flh- (10 is 12 m) mit einer tiefwenenen (25 is 27 m) Boenereitung hinsihtlih es Unkrutufkommens verglihen. Die normllättrige Sorte E.F.B. 33 wies ufgrun einer geringeren Lihttrnsmission zum Unkrutestn eine essere Unkrutunterrükung ls ie hllttlose Sorte uf. Der Mishfruhtnu von Jmes führte im Gegenstz zur Sorte E.F.B. 33 zu einer signifiknten Reuzierung es Unkrutufkommens. Die Boenereitung ht s Unkrutufkommen in Kulturen mit untershielihem Unkrutunterrükungsvermögen niht signifiknt eeinflusst. Die Blttlusihte, er Anteil efllener Pflnzen un ie kumulierten Blttlustge lgen in en Reinsten üer en Werten er Mishsten. Der Befll mit em Ersenwikler konnte urh en Mishfruhtnu mit Tritile jeoh niht wirksm reuziert weren. Shlüsselwörter: Ökologisher Lnu, Pflugsystem, Unkrutunterrükung, Ayrthosiphon pisum Hrris, kumulierte Blttlustge, Cyi nigrin Friius Johnn Heinrih von Thünen Institute, Institute of Orgni Frming, Trenthorst 32, Westeru, Germny University of Kssel-Witzenhusen, Orgni Frming n Cropping Systems, Norhnhofstrße 1, Witzenhusen, Germny Contt: gronle@uni-kssel.e

2 32 A. Gronle, H. Böhm, J. Heß Lnuforsh Appl Agri Forestry Res (64) Introution Wee n pest mngement lrgely influenes rop performne n orgni frmers rely first of ll on ulturl n other preventive mngement strtegies. Effetive wee n pest mngement therefore is hllenge n often wekness in orgni frming. Intensive tillge, e.g., eep moulor ploughing is known s n effetive preventive wee mngement strtegy in orgni frming (Kouwenhoven et l., 2002). The nee to reue the environmentl impt of griulturl mngement prties n to improve soil qulity hs inrese the interest in reution of tillge intensity, e.g., shllow ploughing. Shllow ploughing ws foun to erese fuel onsumption n CO 2 relese from the soil, n to inrese soil ggregte stility n topsoil miroil tivity (Børresen n Njøs, 1994; Chen n Hung, 2009; Curi et l., 1997; Kouwenhoven et l., 2002; Reiosky n Arher, 2007; Vin et l., 2009). However, the results of most stuies inite tht shllow ploughing results in n inrese in nnul, n in prtiulr perennil, wee infesttion in orgni n onventionl frming (Børresen n Njøs, 1994; Brnsæter et l., 2011; Håknsson et l., 1998). Prnitis n Mrinkonis (2005) reporte tht the grin yiel of semi-lefless pes (Pisum stivum L.) erese with eresing ploughing epth whih ws ttriutle to n inrese in wee infesttion. Norml-lefe pes hve etter wee suppressive ility thn semi-lefless pe ultivrs n their yiel performne is therefore less ffete y wee ompetition (Spies et l., 2011). Owing to the low loging resistne, ertion n hrvest of norml-lefe pe rop stns is often prolemti. An interropping with erels improves the loging resistne of norml-lefe winter pes (Urtzk et l., 2011) n the wee suppressive ility of semi-lefless pes (Begn et l., 2011; Corre-Hellou et l., 2011; Poggio, 2005), whih eserves speil ttention in reue tillge systems uner orgni mngement. Pe phis (Ayrthosiphon pisum Hrris) use iret mge to pe plnts y suking plnt sp. Honeyew exretion y pe phis filittes olonistion of sprophyti mouls on the plnt surfe (Bile, 1985). Muh more ritil, however, is their ility to vetor plnt viruses (Brisson n Stern, 2006; Seienglnz et l., 2011). Aphi feeing on pes uses erese in yiel performne n nitrogen-fixing tivity (Hinz, 1991; Miteki n Lm, 1985; Sirur n Brlow, 1984). The pe moth (Cyi nigrin Friius) lrv fees on the eveloping pe sees in the po n high infesttion reues grin yiel n qulity (Huusel-Veistol n Juhiinen, 2006). Although pe moth relte mges re more relevnt in green pe n pe see proution thn in grin pe proution for feeing purposes, reution of moth infesttion in grin pes is importnt to reue the risk for neighouring pe fiels (Huusel-Veistol n Juhiinen, 2006). The severity of pe phi n moth infesttions n therey relte mges re epenent on environmentl n wether onitions s well s on the oiniene of pest ourrene n sensitive pe growth stges (Huusel-Veistol n Juhiinen, 2006; MVen et l., 1999; Shultz n Suke, 2005). MVen et l. (1999) n Thöming et l. (2011) suggeste tht pes shoul e sown erly n only erly-mturing ultivrs shoul e use for pe proution s one preventive mngement strtegy to voi oiniene n therefore high pe phi n moth infesttion levels. Owing to the ft tht time of flowering n mturity is erlier thn in spring pes, ultivtion of winter pes oul e vntgeous to minimize pe phi n moth mges in grin pe proution. Moreover, the t tht o exist inite tht interropping pes n erels n e effetive in reuing n infesttion with some pe pests, e.g., pe phis (Beouss et l., 2008; Beouss, 2009; Seienglnz et l., 2011). The im of this stuy ws to: (1) evlute the effets of ploughing system n interropping on the nnul wee infesttion in semi-lefless n norml-lefe winter pes n their unerlying uses, (2) etermine whether winter pe ultivrs iffering in lef type, s well s in time of flowering n mturity, vry in their suseptiility to pe phi n moth ttks n (3) exmine the impt of pe sole n pe-tritile interropping on n infesttion with pe phis n moths. 2 Mteril n methos 2.1 Site hrteristis, experimentl esign n rop mngement The fiel experiments were onute t the experimentl sttion of the Thünen Institute of Orgni Frming t Trenthorst, Northern Germny (53 46 N, E, 43 m.s.l.) in the sesons 2009/10 n 2010/11. Aoring to the Worl Referene Bse for Soil Resoures, the soil type t the experimentl site ws lssifie s Stgni Luvisol n the soil texture s lom. Post-sowing soil hrteristis re presente in Tle 1. The 30-yer men nnul preipittion t the nerest Ntionl Meteorologil Servie wether sttion in Lüek-Blnkensee (53 52 N, E) is 706 mm with men temperture of 8.8 C. The wether onitions uring the experimentl yers were reore t the experimentl site n re given in Tle 2. Tritile (2009/10, Tritiosele Wittmk) n oilsee rpe (2010/11, Brssi npus L.) were the previous rops t the experimentl site. Tle 1 Chrteristis of the topsoil (0 to 20 m) t the experimentl site in 2009/10 n 2010/ / /11 ph (CCl 2 ) P (CAL, mg kg -1 ) K (CAL, mg kg -1 ) Mg (CCl 2, mg kg -1 ) N t (%) C t (%)

3 A. Gronle, H. Böhm, J. Heß Lnuforsh Appl Agri Forestry Res (64) Tle 2 Air temperture n preipittion uring the 2009/10 n 2010/11 experimentl yer n eprture from 30-yer verge 2009/ /11 Air temperture ( C) Preipittion (mm) Air temperture ( C) Preipittion (mm) Month Averge Deprture 1 Totl Deprture 1 Averge Deprture 1 Totl Deprture 1 August Septemer Otoer Novemer Deemer Jnury Ferury Mrh April My June July Deprture from 30-yer verge (1978 to 2007) Tle 3 Proportion of nnul wee speies in totl wee groun overge n wee speies orer of ominne verge over ll rop stns n ploughing systems t the experimentl fiel in 2009/10 n 2010/ / /11 Sientifi nme % of totl wee overge Orer of ominne % of totl wee overge Orer of ominne Cpsell urs-pstoris (L.) Mei Chenopoium lum L Gleopsis tetrhit L Glium prine L Gernium issetum L Gernium rotunifolium L Lmium purpureum L Myosotis rvensis (L.) Hill Mtriri hmomill L Po nnu L Polygonum persiri L Stellri mei (L.) Vill./Cyr Veroni heerifoli L Vii hirsut (L.) Gry Viol rvensis Murr The experimentl ftor ploughing system onsiste of eep (DP, stule tillge: preision ultivtor, soil epth 8 to10 m; primry tillge: moulor plough to soil epth of 25 to 27 m) n of shllow ploughing (SP). Stule n primry tillge in the shllow ploughing system were performe with skim plough (Stoppelhoel, Zoel-Sthlu, Germny) to soil epth of 4 to 6 m n 10 to 12 m, respetively. Long-term moulor ploughing to soil epth of 25 to 30 m ws performe t the experimentl site efore the strt of the experiment. The ftor rop stn inlue five tretments: the semi-lefless, white-flowere winter pe ultivr Jmes n the norml-lefe, olore-flowere ultivr E.F.B. 33 (shortene EFB) were grown s sole rops (SC, Jmes SC, EFB SC, 80 germinle kernels m -2 ) n in interrops (IC) with tritile (v. Greno, Jmes-TR IC, EFB-TR IC). The interrop onsiste of 40 germinle kernels winter pe n 150 germinle kernels tritile m -2. Component rops were rrnge in lternte rows with 12.5-m row

4 34 A. Gronle, H. Böhm, J. Heß Lnuforsh Appl Agri Forestry Res (64)31-44 istne. A tritile sole rop (Tritile SC, 300 germinle kernels m -2 ) ws grown for wee infesttion omprison purposes. The experimentl lyout ws split-plot esign with four replites. Ploughing systems were rrnge s min plots n rop stns s suplots. The plot size ws m. Sowing ws performe on Septemer 10, 2009 n Otoer 11, As result of the high preipittion in lte summer n utumn 2010 (Tle 2), sowing ws elye y one month in the seon experimentl yer. Crop mngement ourre in orne with Europen orgni frming stnrs (Commission Regultion (EC) No. 889/2008). No mehnil wee ontrol ws performe in the experiments. The most prevlent nnul wee speies in 2009/10 were Lmium purpureum L. n Stellri mei (L.) Vill., wheres Glium prine L. ominte the wee ommunity in the seon experimentl yer. The wee speies omposition t the experimentl fiels n their orer of ominne re liste in Tle Smpling proeures, mesurements, ounts n lultions Groun overge of wees ws estimte five times per plot using retngulr frmes with n re of 0.5 m 2 t the en of stem elongtion in EFB orresponing to the infloresene emergene in Jmes (Tle 4). Annul wee iomss smplings were performe in June (pe flowering/eginning of po evelopment) n July (pe ripening/ mturity) from n re of 0.5 m 2 n 1 m 2 per plot, respetively. The smpling tes n the orresponing rop growth stges re given in Tle 4. Annul wees were ut 1 m ove the soil surfe n rie t 60 C to onstnt weight. The fresh weight n the ry mtter of the wee smples were mesure to estimte the wter ontent of the wee iomss. The ove-groun rop iomss ws s well etermine t the June iomss smpling te n the proportion of wees in totl ovegroun iomss ws lulte. Wee n pe iomss smples were mille (0.5 mm, Foss Tetor 1093, Denmrk) n nlyze to totl nitrogen (N) ontent (CNS elementl nlyzer, HEKAteh, Germny). Simultneous photosynthetilly tive rition (PAR) mesurements ove the rop stn n on the wee nopy level were rrie out using SS1-SunSn Cnopy Anlysis System n referene BF5 Sunshine Sensor (Delt-T Devies, UK). Five mesurements per plot were tken ross the rows on weekly sis strting t the en of winter pe stem elongtion. The proportion of totl PAR trnsmitte to the wee nopy level ws lulte y relting the vlue mesure on the wee nopy level to the inient PAR ove the rop stn. The ensity of live pe phis (numer per shoot tip) ws ounte n the iniene (proportion of infeste plnts) ws etermine uring the entire infesttion perio twie or three times week in eep ploughe plots oring to the EPPO stnrs (EPPO, 2005). The pe BBCH growth stges were reore t eh ssessment. Cumultive phi-ys were lulte following Ruppel (1983). Winter pe grin smples of plot omine hrvest from n re of 17.5 m 2 were use to etermine the pe moth infesttion level. In oing so, four times 200 grins per plot were sreene for symptoms of ttk. 2.3 Sttistil Anlysis Owing to the iffering sowing tes, the sttistil nlysis ws onute seprtely for oth experimentl yers. Winter pe ropping system n ultivr were nlyze s omine ftor rop stn, in orer to llow omprison with tritile sole rops onerning the infesttion with nnul wees. ANOVA followe y Tukey s post ho ws performe y using the MIXED proeure of SAS 9.2. Wee overge t were trnsforme using rsine squre root trnsformtion, wheres t for wee iomss n wee N uptke were log trnsforme to hieve normlity. Pro NLMIXED ws use to fit nonliner regression moels. A negtive inomil moel ws fitte to the phi ensity t using Pro GLIMMIX to ount for overispersion in oth experimentl yers (Littell et l., 2006; Liu n Cel, 2008; O Hr n Kotze, 2010). A inomil istriution n the logit link in Pro GLIMMIX were use for the nlysis of the pest iniene t (Men et l., 2002; Piepho, 1999). Due to the ft tht phi ounting n the PAR mesurements were me on non-equl time intervls, unequl repete mesure nlysis ws performe (Littell et l., 2006). Tle 4 Dtes of wee overge estimtion n iomss smplings with the orresponing rop growth stges (BBCH) in 2009/10 n 2010/ / /11 Dte 2010 Growth stge Dte 2011 Growth stge EFB Jmes Tritile EFB Jmes Tritile Groun overge of wees 22 April My Wee n rop iomss smpling 1 15 June June Wee iomss smpling 2 19 July July

5 A. Gronle, H. Böhm, J. Heß Lnuforsh Appl Agri Forestry Res (64) Results 3.1 Wees Wee groun overge, wee iomss n wee-rop iomss reltionship The experimentl ftor rop stn h signifint effet on the wee groun overge in oth experimentl yers. The wee groun overge ws highest in Jmes sole rops n lest in tritile sole rops n i not iffer signifintly etween EFB n Jmes in either sole rops or in interrops (Tle 5). Interropping winter pes n tritile tene to reue the wee groun overge in 2009/10 n resulte in signifintly lower wee groun overge vlues in 2010/11. Also, the proportion of wees in totl ovegroun iomss n the wee iomss in 2009/10 were signifintly ffete y the experimentl ftor rop stn. Aitionlly, the nlysis of vrine showe signifint smpling te rop stn intertion for the wee iomss t in 2010/11. The proportion of wees in the totl ovegroun iomss ws signifintly greter in Jmes sole rops thn in the other exmine rop stns in oth experimentl yers (Tle 5). Jmes-tritile interrops exhiite signifintly lower proportions of wees in totl ovegroun iomss thn Jmes sole rops. There were no signifint ifferenes etween EFB sole rops, tritile sole rops n winter pe-tritile interrops in 2009/10. Unlike in 2009/10, EFB sole ropping resulte in signifintly higher proportion of wees in totl ovegroun iomss ompre with tritile sole ropping n interropping in 2010/11. The signifintly highest wee iomss umultion ws etermine in Jmes sole rops in oth experimentl yers (Tle 5, Figure 1). The EFB sole n interrops were foun to hve signifintly lower wee iomss vlues thn Jmes n tritile sole s well s interrops in 2009/10. Besies, there ws no signifint ifferene etween EFB sole n EFB-tritile interrops onerning the wee iomss umultion t the June s well t the July smpling te in 2009/10, wheres Jmes-tritile interropping resulte in signifintly lower wee iomss umultion ompre with Jmes sole ropping t oth smpling tes in the sme yer. The wee infesttion in 2010/11 ws higher thn in the previous experimentl yer (Tle 5, Figure 1). EFB sole rops showe signifintly lower iomss umultion thn Jmes sole rops in 2010/11 (Tle 5). In ontrst, no vrietl ifferene ws revele in winter pe-tritile interrops. Interropping winter pes n tritile reue the iomss umultion t the first smpling te inepenent of the pe ultivr. At the seon smpling te, however, signifint lower wee iomss umultion in the interrop thn in the sole rop ws solely present for ultivr Jmes. The wee iomss umultion in tritile sole rops ws signifintly lower thn tht in EFB sole rops t the first smpling te n omprle t the seon smpling te. Moreover, no signifint ifferenes ourre etween tritile sole rops n winter pe-tritile interrops t oth smpling tes in 2010/11. Tritile ws foun to hve lower ovegroun iomss umultion t pe flowering in 2009/10 (Tritile SC: 335.8, EFB-TR IC: 123.5, Jmes-TR IC: g.m. m -2 ) thn in 2010/11 (Tritile SC: 663.2, EFB-TR IC: 480.7, Jmes-TR IC: g.m. m -2 ). Therefore, totl rop iomss umultion of tritile sole rops n winter pe-tritile interrops ws onsierly lower thn tht in 2010/11 (Figure 1). There ws reltionship etween rop n wee ovegroun iomss umultion t the June smpling te (Figure 1). Wee ovegroun iomss exponentilly erese s the rop ovegroun iomss inrese, most notly in the seon experimentl yer. There ws neither signifint intertion omprising the experimentl ftor ploughing system nor signifint Tle 5 Effet of rop stn on the wee infesttion in 2009/10 n 2010/11. Vlues re mens ± SEM 2009/ /11 Wee groun overge (%) Wee iomss in totl ovegroun iomss (%) Wee iomss (g.m. m -2 ) Crop stn April/My June June July EFB SC 44.0 ± ± ± ± 3.7 EFB-TR IC 33.4 ± ± ± ± 2.9 Jmes SC 53.4 ± ± ± ± 19.6 Jmes-TR IC 43.6 ± ± ± ± 3.7 Tritile SC 26.4 ± ± ± ± 5.3 EFB SC 16.6 ± ± ± ± 9.6 EFB-TR IC 7.4 ± ± ± ± 3.2 Jmes SC 18.0 ± ± ± ± 20.2 Jmes-TR IC 6.3 ± ± ± ± 6.6 Tritile SC 5.5 ± ± ± ± 4.0 Mens within eh olumn n experimentl yer with ifferent letters re signifintly ifferent (P < 0.05))

6 36 A. Gronle, H. Böhm, J. Heß Lnuforsh Appl Agri Forestry Res (64)31-44 Wee ovegroun iomss [g.m. m -2 ] EFB SC EFB-TR IC Jmes SC Jmes-TR IC Tritile SC A 2009/10 y = e x R 2 = 0.14 B 2010/11 y = 2,784.5 e x R 2 = ,000 Crop ovegroun iomss [g.m. m -2 ] ,000 Crop ovegroun iomss [g.m. m -2 ] Figure 1 Reltionship etween wee n rop ovegroun iomss t the June smpling te in 2009/10 (A) n 2010/11 (B) inepenent of ploughing system. n inite tht exponentil regression is signifint t P < 0.01 n P < Tle 6 Effet of ploughing system on wee prmeters in 2009/10 n 2010/11. Vlues re mens of one rting/smpling te (wee groun overge, wee iomss in totl ovegroun iomss) or two smpling tes (wee iomss, N ontent, N uptke n ry mtter ontent) ± SEM Ploughing system 2009/ /11 DP SP DP SP Wee groun overge (%) 37.4 ± ± ± ± 1.4 Wee iomss in totl ovegroun iomss (%) 6.5 ± ± ± ± 4.1 Wee iomss (g.m. m -2 ) 26.5 ± ± ± ± 11.7 Wee iomss N ontent (%) 1.72 ± ± ± ± 0.07 Wee iomss N uptke (kg h -1 ) 3.9 ± ± ± ± 1.6 Wee iomss ry mtter ontent (%) 27.4 ± ± ± ± 0.7 Mens on the sme line within the sme experimentl yer with ifferent letters re signifintly ifferent (P < 0.05) ploughing system min effet for wee infesttion prmeters. Wee groun overge, proportion of wees in totl ovegroun iomss n wee ovegroun iomss fter shllow n eep ploughing thus revele omprle results (Tle 6). Also, totl rop ovegroun iomss umultion i not iffer signifintly etween shllow n eep ploughing (t not shown) Wee N ontent n N uptke in ovegroun iomss The N ontent of the wee iomss ws signifintly ffete y rop stn min effet in 2009/10 n smpling te rop stn intertion in 2010/11. The highest wee N ontent ws etete in EFB sole rops in oth experimentl yers (Tle 7). At the first smpling te in June, wees in EFB-tritile interrops were foun to hve signifintly lower wee N ontents thn EFB sole rops, wheres no signifint ifferenes in wee N ontent ourre etween EFB sole n interrops t the July smpling te. Also, the wee iomss in Jmes sole rops possesse signifintly lower N ontent thn tht in EFB sole rops. Unlike in 2009/10, the wee iomss N ontent in Jmes sole n interrops i iffer signifintly in 2010/11with lower vlues in the interrop t the June n higher vlues t the July smpling te. Tritile sole ropping resulte in tenentilly or signifintly lower wee iomss N ontent thn EFB sole or interropping. No signifint ifferenes were foun etween tritile n Jmes sole rops in 2009/10 or etween tritile sole rops n Jmes-tritile interrops in oth experimentl yers. The ploughing system i not ffet the wee iomss N ontent in 2009/10, wheres signifintly higher vlues were foun fter shllow ploughing in 2010/11 (Tle 6). The sttistil nlysis of the wee N uptke in ovegroun iomss revele signifint rop stn min effet in 2009/10 n signifint smpling te rop stn intertion in 2010/11. Jmes sole rops showe the

7 A. Gronle, H. Böhm, J. Heß Lnuforsh Appl Agri Forestry Res (64) highest wee N uptke of ll rop stns n signifintly higher vlues thn EFB sole rops in oth experimentl yers (Tle 7). Moreover, the wee N uptke ws signifintly higher in Jmes-tritile interrops thn in EFB-tritile interrops in 2009/10, wheres no signifint ifferenes were foun etween winter pe-tritile interrops in 2010/11. Tritile sole rops took up n intermeite position etween rop stns with Jmes n those with EFB in 2009/10. In 2010/11, however, there were no signifint ifferenes etween tritile sole n winter pe-tritile interrops with regr to wee N uptke. The ploughing system h no effet on the wee N uptke in either experimentl yer (Tle 6) Wee ry mtter ontent A smpling te rop stn intertion n rop stn min effet signifintly ffete the ry mtter ontent of the wee iomss in 2009/10 n 2010/11, respetively. The ry mtter ontent of the wee iomss i not iffer signifintly etween winter pe sole n interrops in 2009/10, wheres winter pe-tritile interrops h signifintly higher vlues thn winter pe sole rops in 2010/11 (Tle 7). Crop stns with Jmes showe higher wee iomss ry mtter ontent thn those with ultivr EFB. Furthermore, the wee iomss in tritile sole rops ws omprle to the level in Jmes-tritile interrops exept for the July smpling te in 2009/10. Neither signifint min effet nor n intertion ontining the experimentl ftor ploughing system h n impt on the ry mtter ontent in 2009/10. In ontrst, eep ploughing resulte in signifintly higher wee iomss ry mtter ontent thn shllow ploughing in 2010/11 (Tle 6) Trnsmission of inient photosynthetilly tive rition to wee nopy level The proportion of inient photosynthetilly tive rition (PAR) trnsmitte to the wee nopy level ws signifintly ffete y mesurement te rop stn intertion in oth experimentl yers n y rop stn ploughing system intertion in 2009/10. The PAR trnsmission to the wee nopy level ws signifintly higher with winter pe Jmes thn with EFB in sole s well s in interrops throughout the omplete perio of mesurement in 2009/10 (Figure 2A). Jmes sole rops were foun to hve signifintly higher vlues thn Jmes-tritile interrops until the en of flowering in Jmes (BBCH 67, 17 My), ut therefter lower PAR trnsmission ws mesure in Jmes sole rops. There ws no signifint ifferene etween EFB sole n interrops t the eginning of the PAR mesurement in 2009/10. Susequently, PAR trnsmission ws signifintly lower in EFB sole rops thn in EFB interrops. This tren ontinue until the en of My, respetively the infloresene emergene (BBCH 51) in EFB. Therefter, sole n interroppe EFB rop stns showe omprle PAR trnsmission. The PAR trnsmission to the wee nopy in tritile sole rops ws etween the level of Jmes n EFB rop stns until the mile of My. After the eginning of ooting, tritile sole ropping resulte in the highest PAR trnsmission ompre with ll other exmine rop stns. The 2010/11 t evite to lrge extent from t gthere in the first experimentl yer. The PAR trnsmission ws s well highest in Jmes sole rops until the en of My (BBCH 65) n tenentilly or signifintly higher thn in EFB sole rops t ll mesurement tes (Figure 2B). Winter pe interrops n tritile sole rops, however, i not iffer signifintly uring the initil phse of mesurement. Moreover, Tle 7 Effet of rop stn on wee iomss N ontent, N uptke n ry mtter ontent t two smpling tes in 2009/10 n 2010/11. Vlues re mens ± SEM Wee iomss N ontent (%.m.) N uptke (kg h -1 ) Dry mtter ontent (%) Crop stn June July June July June July 2009/10 EFB SC 2.56 ± ± ± ± ± ± 3.7 EFB-TR IC 1.95 ± ± ± ± ± ± 2.6 Jmes SC 1.65 ± ± ± ± ± ± 2.1 Jmes-TR IC 1.54 ± ± ± ± ± ± 1.1 Tritile SC 1.73 ± ± ± ± ± ± /11 EFB SC 2.33 ± ± ± ± ± ± 1.5 EFB-TR IC 1.51 ± ± ± ± ± ± 0.6 Jmes SC 1.63 ± ± ± ± ± ± 0.6 Jmes-TR IC 1.30 ± ± ± ± ± ± 1.4 Tritile SC 1.23 ± ± ± ± ± ± 2.1 Mens within eh experimentl yer n olumn with ifferent letters re signifintly ifferent (P < 0.05)

8 38 A. Gronle, H. Böhm, J. Heß Lnuforsh Appl Agri Forestry Res (64)31-44 PAR trnsmitte [% of inient PAR] A 2009/10 B 2010/11 EFB SC EFB-TR IC Jmes SC Jmes-TR IC Tritile SC 23-Apr 7-My 21-My 4-Jun 18-Jun 23-Apr 7-My 21-My 4-Jun 18-Jun Figure 2 Proportion of PAR trnsmitte to the wee nopy level in sole rops (SC) n interrops (IC) of winter pes n tritile in 2009/10 (A) n 2010/11 (B) verge over oth ploughing systems. Vlues re mens ± SEM (error rs). Different letters inite signifint ifferenes (P < 0.05) etween rop stns t the sme mesurement te. signifintly lower PAR trnsmission ws revele in these three rop stns ompre with the winter pe sole rops until the eginning of My. Therefter, the ourse of the PAR trnsmission in interrops prllele the tren in tritile sole rops with EFB-tritile interrops emonstrting the lowest n tritile sole rops the highest vlue. Contrry to the reltively ontinuous tren in winter pe sole rops, the PAR trnsmission in tritile sole n winter pe-tritile interrops flutute ll through June. At the sme time, EFB sole ropping resulte in the lowest n Jmes sole ropping mostly in the highest PAR trnsmission to the wee nopy level. The signifint rop stn ploughing system intertion in 2009/10 ws use y signifintly higher PAR trnsmission in tritile sole rops fter shllow ploughing (52.7 %) thn fter eep ploughing (43.4 %). In ontrst, the ploughing system i not signifintly influene the PAR trnsmission in ll other rop stns. In 2010/11, ny effet omprising the experimentl ftor ploughing system signifintly ffete the PAR trnsmission to the wee nopy level. 3.2 Pests Pe phi ensity n iniene In the first experimentl yer, first pe phis were oserve on 2 n June t the eginning of flowering in EFB (BBCH 60) n t flowering elining in Jmes (BBCH 67). The numer of pe phis on sole n interroppe EFB inrese until the elining of EFB flowering (BBCH 67), ut therefter erese ontinuously (Figure 3A). The proportion of infeste EFB plnts in sole n interrops showe omprle trens to the pe phi ensity t in EFB (Figure 3E). The highest proportion of infeste EFB plnts ws etete 26 ys post infesttion, nlogous to the highest phi ensity. Shortly fter the etetion of first phis, the numer of pe phis on EFB n the proportion of infeste plnts were signifintly lower when interropping thn sole ropping ws performe. At the mximum infesttion level, EFB sole rops were foun to hve 71 % phi-infeste plnts with 21 phis per shoot tip, wheres 8 phis per shoot n 44 % infeste plnts were etete in EFB-tritile interrops. Jmes phi infesttion peke 6 ys post infesttion in interrops n 8 ys fter the etetion of first phis in sole rops t the en of flowering (BBCH 69) respetively the eginning of po evelopment in Jmes (BBCH 71) (Figure 3C, G). No further phis were etete 22 ys n 26 ys post infesttion in sole n interroppe Jmes, respetively. Interropping Jmes n tritile signifintly reue the ensity n iniene of pe phis ompre with Jmes sole rops. The mximum numer of phis per Jmes shoot tip ws y 6 phis lower thn in EFB sole rops, wheres no ifferene ws foun etween the mximum ensity in interroppe EFB n Jmes. Pe phis were foun on 80 % of sole roppe n on 65 % of interroppe Jmes plnts t the infesttion pek, whih ws higher thn with winter pe ultivr EFB. Low phi infesttion levels were foun in 2010/11, with mximum numer of 3 phis per shoot tip in oth pe ultivrs 23 ys post infesttion t full flowering in EFB (BBCH 65) n the eginning of po evelopment in Jmes (BBCH 72) (Figure 3B, D). The pe phi iniene flutute etween 0 % n 26 % in EFB sole rops respetively 8 % in EFB interrops (Figure 3F). A similr rnge of vlues ws foun for Jmes sole n interrops (Figure 3H). The phi infesttion perio ws simultneous in oth winter pe ultivrs. Despite low infesttion level, there were signifintly higher numers of pe phis per shoot tip n more infeste plnts in winter pe sole rops thn in interrops t most ounting tes.

9 A. Gronle, H. Böhm, J. Heß Lnuforsh Appl Agri Forestry Res (64) Aphis shoot tip A 2009/10 EFB EFB SC EFB-TR IC B 2010/11 EFB EFB SC EFB-TR IC Aphis shoot tip C 2009/10 Jmes Jmes SC Jmes-TR IC D 2010/11 Jmes Jmes SC Jmes-TR IC E 2009/10 EFB EFB SC EFB-TR IC F 2010/11 EFB EFB SC EFB-TR IC Infeste plnts [%] G 2009/10 Jmes H 2010/11 Jmes Infeste plnts [%] Jmes SC Jmes-TR IC Jmes SC Jmes-TR IC Dys post infesttion Dys post infesttion /10 BBCH EFB /11 BBCH EFB /10 BBCH Jmes 2010/11 BBCH Jmes Figure 3 Density (numer of phis per shoot tip, A-D) n iniene (proportion of infeste pe plnts, E-H) of pe phis in sole n interroppe winter pes in 2009/10 (A, C, E, G) n 2010/11 (B, D, F, H) with the orresponing growth stges of Jmes n EFB. First phis were etete on 2 n June, 2010 n 19 th My, Vlues re mens ± SEM (error rs). Asterisks inite signifint ifferenes (P < 0.05) etween sole n interrops.

10 40 A. Gronle, H. Böhm, J. Heß Lnuforsh Appl Agri Forestry Res (64) Cumultive phi-ys Cumultive phi-ys were signifintly higher in EFB sole rops n interrops thn in the orresponing Jmes rop stns in 2009/10 (Tle 8). In ition, interropping winter pes n erels signifintly reue umultive phi-ys. Compre to the first experimentl yer, umultive phiy vlues were onsierly lower in 2010/11. The experimentl ftor rop stn i not signifintly ffet the vlues in the seon experimentl yer. There ws, however, the teneny of lower umultive phi-ys in winter pe-tritile interrops thn in winter pe sole rops. Tle 8 Effet of rop stn on umultive phi-ys in 2009/10 n 2010/11. Vlues re mens ± SEM Cumultive phi-ys Crop stn 2009/ /11 EFB SC 400 ± ± 2 EFB-TR IC 139 ± ± 4 Jmes SC 128 ± ± 9 Jmes-TR IC 56 ± 3 11 ± 4 Mens within eh olumn with ifferent letters re signifintly ifferent (P < 0.05) Pe iomss N ontent The pe iomss N ontent t the June iomss smpling te ws signifintly higher in sole roppe thn in interroppe winter pes in oth experimentl yers, with the exeption tht sole roppe Jmes solely tene to hve higher vlues thn interroppe Jmes in 2010/11 (Tle 9). There ws no signifint ifferene in pe iomss N ontent etween winter pe ultivrs in 2009/10, wheres sole n interroppe EFB were etete to hve signifintly higher vlues thn the orresponing rop stns with Jmes in 2010/11. Tle 9 Effet of rop stn on pe iomss N ontent t the June iomss smpling. Vlues re mens ± SEM Pe iomss N ontent (%) Crop stn 2009/ /11 EFB SC 3.00 ± ± 0.04 EFB-TR IC 2.78 ± ± 0.05 Jmes SC 3.10 ± ± 0.04 Jmes-TR IC 2.60 ± ± 0.04 Mens within eh olumn with ifferent letters re signifintly ifferent (P < 0.05) Pe moth lrve mge pes A signifintly higher proportion of pe moth lrve-mge winter pes ws etete in winter pe ultivr EFB, sole or interroppe, thn in ultivr Jmes in oth experimentl yers (Tle 10). There ws no ifferene in proportion of mge pes etween sole n interrops in 2009/10. Interropping winter pes n tritile in 2010/11, however, signifintly inrese the proportion of mge pes. Furthermore, winter pe ultivr EFB showe omprle vlues in oth experimentl yers, wheres Jmes ws foun to hve onsierly higher proportion of mge pes in 2010/11. Tle 10 Effet of rop stn on the proportion of pe moth lrve-mge pes. Vlues re mens ± SEM Pe moth lrve mge pes (%) Crop stn 2009/ /11 EFB SC 32.3 ± ± 1.1 EFB-TR IC 37.6 ± ± 1.6 Jmes SC 7.4 ± ± 1.0 Jmes-TR IC 4.3 ± ± 1.2 Mens within eh olumn with ifferent letters re signifintly ifferent (P < 0.05) 4 Disussion 4.1 Wee infesttion The wee infesttion level iffere onsierly etween oth experimentl yers. Annul wees overe higher proportion of the soil in the exmine rop stns in spring in the first experimentl yer ompre with 2010/11 (Tle 5). However, the wee iomss umultion in 2010/11 mostly exeee the level of the first experimentl yer. This my e ue to ifferenes in sowing te, wether onitions n in wee speies omposition t the experimentl fiels (Tle 2, 3). L. purpureum n S. mei, the most ominnt wee speies in 2009/10, were lrey well-evelope n overe lrge prt of the soil efore winter, wheres few sttere wees were present t the 2010/11 experimentl fiel efore winter n in erly spring. L. purpureum, however, egn to senese t the en of My, whih resulte in high wee iomss ry mtter ontent t the July smpling te (Tle 7). Owing to the roughty onitions in spring 2011, wee growth n evelopment ws reue until the onset of rinfll in the mile of My 2011, ut inrese onsierly therefter. This ws most notle for the preominnt wee speies G. prine, whih resulte in severe wee prolems. Thus, n erly wee infesttion, with erese towrs mturity, ws present t the experimentl fiels in 2009/10, wheres lte-seson wee infesttion ominte in the seon experimentl yer. Wee iomss umultion n N uptke, s well s the proportion of wee iomss in totl ovegroun iomss, were signifintly higher in Jmes thn in EFB sole rops (Tle 5, 7, Figure 1). The norml-lefe winter pe ultivr, thus, etter suppresse wees thn the semi-lefless ultivr, whih orreltes well with the literture for spring n winter pes (Spies et l., 2011; Urtzk, 2010; Urtzk et l., 2011). EFB sole rops were foun to hve lower PAR trnsmission to the wee nopy level thn Jmes sole rops

11 A. Gronle, H. Böhm, J. Heß Lnuforsh Appl Agri Forestry Res (64) (Figure 2), whih my e relte to higher pe iomss umultion (Figure 1). The etter wee suppressive ility of the norml-lefe winter pe EFB my therefore e ssoite with lower light vilility for wees. The wee groun overge t the en of April 2010, respetively the eginning of My 2011, however, i not iffer signifintly etween semi-lefless winter pe ultivr Jmes n norml-lefe ultivr EFB (Tle 5). The PAR trnsmission to the wee nopy level in Jmes sole rops mrginlly or signifintly exeee the level of EFB sole rops t the sme time (Figure 2). PAR trnsmission vlues, however, were t high level in oth winter pe sole rops, whih my e responsile for the slight vrietl ifferene with regr to wee groun overge. The high wee iomss proution in Jmes sole rops in the seon experimentl yer (Tle 5) ws relte to omplete rop stn overgrowth with G. prine, whih inites goo soil nitrogen supply. This ws ue to the short plnt height of Jmes eing within rnge of 23 to 31 m t flowering. The wee growth ggrvtion towrs mturity my s well hve ontriute to the inrese in wee iomss in Jmes sole rops from the June to the July smpling te in 2010/11, whih stns in ontrst to ll other rop stns. The tll growing ultivr EFB exhiite severe loging fter flowering in sole rops. However, wee overgrowth in loge rop stns of sole roppe EFB ws oservle neither in 2009/10 nor in 2010/11 n the wee iomss umultion remine t the sme level (2009/10) or erese etween the June n the July smpling te (2010/11, Tle 5). Interropping winter pe Jmes n tritile s well s sole ropping tritile resulte in signifintly lower wee iomss umultion, proportion of wee iomss in totl ovegroun iomss n wee N uptke thn Jmes sole ropping (Tle 5, 7). Moreover, Jmes-tritile interrops showe lower wee groun overge vlues thn Jmes sole rops (Tle 5). These results onfirm the effiient wee suppressive ility of pe-erel interrops tht hs een shown in previous stuies for interrops of semi-lefless winter s well s spring pes n erels (Begn et l., 2011; Corre- Hellou et l., 2011; Huggr-Nielsen et l., 2001; Urtzk, 2010). Despite higher wee pressure towrs mturity in 2010/11, resulting in higher wee iomss umultion n N uptke in Jmes sole rops ompre to the first experimentl yer, vlues in Jmes-tritile interrops h omprle level in oth experimentl yers (Tle 5, 7). This my e relte to prolems in winter tritile emergene, estlishment n winter survivl in 2009/10, whih involve poor sole n interroppe tritile stns with only 30 % of the projete plnt ensity n y 49 to 74 % lower ovegroun iomss umultion thn in 2010/11. Corre-Hellou et l. (2011) suggeste tht the higher wee suppression in semi-lefless pe-rley interrops ompre to pe sole rops is minly ue to higher nitrogen ompetition in se of low soil N vilility. The uthors lso foun tht high soil N vilility ontriutes to n inrese in rop lef re. They onlue tht wee suppression is uner these onitions ttriutle to strong light ompetition. Aprt from the June iomss smpling in 2010/11, the wee iomss N ontent of Jmes-tritile interrops ws omprle or signifintly higher thn in Jmes sole rops (Tle 7). In ition, tritile sole ropping resulte solely in signifintly lower wee iomss N ontent thn Jmes sole ropping t the first smpling te in 2010/11. Aprt from tht, omprle or signifintly higher vlues were etete in the wee iomss from tritile sole rops. These results inite tht nitrogen ompetition oes not suffiiently explin the high wee suppressive ility in Jmes-tritile interrops n tritile sole rops. The PAR trnsmission to the wee nopy level ws signifintly higher in Jmes sole rops thn in Jmes-tritile interrops n tritile sole rops until the en of My, ut i therefter mostly not iffer from or exee the level of Jmes sole rops (Figure 2). Thus, in the se of the erly wee pressure in 2009/10, the high wee suppressive ility of Jmes-tritile interrops n tritile sole rops my hve preomintely originte from stronger light ompetition thn in Jmes sole rops. The non-signifint ifferene in PAR trnsmission to the wee nopy level etween Jmes sole rops n Jmes-tritile interrops fter the en of My in 2010/11 (Figure 2B) emonstrtes tht shing nnot e responsile for the signifintly lower lte-seson wee infesttion in Jmes-tritile interrops in the seon experimentl yer. The wee iomss ry mtter ontent i not iffer signifintly etween Jmes sole rops n Jmes-tritile interrops t either the June or the July iomss smpling in 2009/10. In ontrst to 2009/10, wee iomss in Jmes-tritile interrops ws foun to hve signifintly higher ry mtter ontent thn tht of Jmes sole rops in the seon experimentl yer (Tle 7). Our results suggest tht the goo wee suppressive ility of Jmes-tritile interrops ws ue to higher wter ompetition ompre to Jmes sole rops. This oservtion is in orne with results of Mohler n Liemn (1987) for spring pe-rley interrops. The presumly higher rop-wee ompetition for wter in Jmes-tritile interrops thn in Jmes sole rops in 2010/11 my hve resulte from the roughty onitions in spring 2011 inhiiting the iomss formtion in Jmes ut not in tritile. Despite the low tritile ovegroun iomss umultion in 2009/10, the wee infesttion in EFB-tritile interrops ws omprle to the low wee infesttion level in EFB sole rops n signifintly lower thn in the tritile sole rops (Figure 1A, Tle 5). Owing to the sent ompetition etween winter pes n tritile in the interrop, the rop iomss umultion in EFB-tritile interrops otine the level of the iomss umultion in EFB sole rops (Figure 1A). For this reson, EFB-tritile interrops prllele the PAR trnsmission ourse of EFB sole rops on higher level until the en of My, ut therefter rehe the low level of EFB sole rops (Figure 2A). The teneny of lower wee iomss vlues in the interrop my therefore e expline y higher rop-wee nitrogen ompetition thn in the sole rop, whih resulte in lower wee iomss N ontent (Tle 7). Interropping EFB n tritile signifintly reue the wee infesttion ompre to EFB sole ropping t the June

12 42 A. Gronle, H. Böhm, J. Heß Lnuforsh Appl Agri Forestry Res (64)31-44 iomss smpling in 2010/11, wheres no ifferenes were foun t the July smpling te in the seon experimentl yer (Tle 5). The effetive wee suppressive ility of EFB-tritile interrops in June n e ttriute, in prt, to signifintly lower PAR trnsmission (Figure 2B). In ition, the wee iomss N ontent ws signifintly lower n the ry mtter ontent signifintly higher in the EFB-tritile interrop thn in the EFB sole rop (Tle 7). We might therefore suppose higher nitrogen n wter ompetition in the interrop to e importnt ftors for the low wee iomss umultion in EFB-tritile interrops t the June smpling te, too. The PAR trnsmission in EFB sole rops showe strong eresing tren towrs mturity resulting in signifintly lower PAR trnsmission level thn in EFB-tritile interrops fter the mile of My (Figure 2B). Moreover, the wee iomss nitrogen ontent ws foun to e ientil in EFB sole n interrops t the July iomss smpling te (Tle 7). The similr wee iomss umultion in EFB sole n EFB-tritile interrops in July my thus e ttriute to hnge in PAR trnsmission n nitrogen vilility in oth rop stns. Most stuies suggest tht erese in ploughing epth is orrelte with n inrese in nnul, n in prtiulr perennil, wee infesttion (Børresen n Njøs, 1994; Brnsæter et l., 2011; Gruer n Clupein, 2009; Kouwenhoven et l., 2002; Prnitis n Mrinkonis, 2005). Despite ifferenes in wee omposition n wee pressure t the experimentl sites in 2009/10 n 2010/11, eep n shllow ploughing i not iffer signifintly in nnul wee groun overge, iomss umultion n N uptke or in the proportion of nnul wee iomss in totl ovegroun iomss in oth experimentl yers (Tle 6). Our t therefore iffer from those reporte y others. Interestingly the ploughing system neither ffete rop stns with low wee suppressive ility, e.g., Jmes sole rops nor rops stns possessing goo wee suppression, s for instne EFB-tritile interrops. Even the signifintly higher PAR trnsmission in tritile sole rops in 2009/10 in onsequene of lower emergene n higher winter kill rte of tritile fter shllow ploughing i not influene the nnul wee infesttion. The wee iomss N n ry mtter ontent were ffete y the ploughing system in 2010/11 ut not in 2009/10 (Tle 6). The signifintly higher wee iomss N ontent n the signifintly lower ry mtter ontent fter shllow ploughing in 2010/11 i not, however, our ouple with n inrese in wee iomss. These results inite tht reution of the ploughing system i not lter the germintion environment or onsierly hnge the nutrient n wter vilility for nnul wees. 4.2 Pe pests Pe phi infesttion The ourrene of pe phis n the urtion of the infesttion were losely relte to the pe flowering perio. Flowering ourre erlier in Jmes thn in EFB, most notly in 2009/10 (Figure 3). Tht is the reson why the phi infesttion of winter pe Jmes egn t Jmes min flowering n peke etween the en of flowering n the eginning of po evelopment, wheres first phis on EFB were oserve t the eginning of EFB flowering n the mximum infesttion level ws foun to e in the perio etween EFB min n elining flowering (Figure 3). Owing to the lte pperne of pe phis in 2009/10, the infesttion perio ws shorter in Jmes thn in EFB. The shorter infesttion perio ouple with lower phi ensity resulte in signifintly lower umultive phi-ys in sole roppe Jmes thn in sole roppe EFB (Tle 8). These results inite tht erly-flowering winter pes will e mge to lesser extent thn lte-flowering winter pes. MVen et l. (1999) suggeste s well tht spring pe sowing time shoul e s erly s possile to voi the oiniene of flowering n high phi ourrene. The omprle ensity n iniene of pe phis s well s the non-signifint ifferene in umultive phi-ys etween oth pe ultivrs in 2010/11 (Figure 3, Tle 8) resulte from the low ourrene of pe phis n the slightly lter flowering te in Jmes. Low phi ensity n iniene in 2010/11 might e ttriute to spring rought. Miteki et l. (1986) lso foun low pe phi ensities uner rought onitions in spring n erly summer. Pek phi ensity ws lower in sole roppe Jmes thn in sole roppe EFB, wheres the proportion of infeste pe plnts tene to e higher in Jmes sole rops ompre to EFB sole rops in 2009/10 (Figure 3). Owing to the less ville spe on tenrils thn on leflets, the evelopment of phi olonies is more restrite on semi-lefless thn on norml-lefe pes (Sorok n Mky, 1990). As onsequene, Jmes might hve supporte fewer pe phis whih involve higher numer of infeste plnts. The erlier eline of the phi infesttion in Jmes sole rops in 2009/10 ourre in onjuntion with n inrese in ir temperture. This oservtion is in orne with other uthors, who suggeste tht verse environmentl onitions ffet pe phis to greter extent on semi-lefless or lefless pes thn on norml-lefe pes (Buhmn n Cuington, 2009; Legrn n Bros, 2000; Sorok n Mky, 1990). In greement with the finings of Seienglnz et l. (2011) for spring pes, we foun tht pe phis ppere t the sme time in winter pe sole n interrops (Figure 3). These t i not support the hypothesis tht tritile ts s rrier n prevents n phi ttk of interroppe winter pe ultivrs with short plnt height t flowering like Jmes. Interropping, however, signifintly reue pe phi ensity n iniene s well s umultive phi-ys most notly with the high infesttion level in 2009/10 (Figure 3, Tle 8). Similr results hve een emonstrte y Beouss (2009) for semi-lefless winter pe-urum whet interrops. Ptriquin et l. (1988) ompre the numer of Aphis fe in f en (Vii f L.) sole rops n f enerel interrops uner orgni onitions. They foun tht the phi ensity n the lef N ontent were signifintly higher in sole rops thn in interrops. The uthors onlue tht olonistion s well s reproution of phis my e reue y the nitrogen ompetition in interrops. We foun mostly signifintly lower iomss N ontents in inter-

13 A. Gronle, H. Böhm, J. Heß Lnuforsh Appl Agri Forestry Res (64) roppe winter pes uring the infesttion perio with pe phis (Tle 9), whih onfirms these previous oservtions in f en-erel interrops. Thus, the lower pe phi infesttion in winter pe-tritile interrops might e ttriute to lower nitrogen sttus in interroppe winter pes. Previous stuies, however, hve reporte ontritory finings pertining to the effet of pe nitrogen supply on the pe phi reproution uner greenhouse onitions. Morvvej n Htefi (2008) showe tht the phi reproution inrese with inresing nitrogen ontent in pe leves, wheres Buhmn n Cuington (2009) i not fin reltionship etween pe nitrogen supply n phi reproution. Another possile explntion for the iffering phi infesttion in sole n interroppe winter pes oul e ifferene in phi feeing ehviour ue to vrition in plnt nitrogen sttus. Poner et l. (2000) foun tht phis took longer to reh the phloem sp n showe shorter feeing perio on rley uner nitrogen limite thn uner non-nitrogen limite onitions. Aphi ensity n iniene ws foun to erese erlier in Jmes-tritile interrops thn in Jmes sole rops in 2009/10 (Figure 3C, G). This oservtion is in orne with Seienglnz et l. (2011), who reporte tht phi olonies erese erlier in semi-lefless spring pe-erel interrops thn in pe sole rops. The uthors onlue tht n erlier ourrene n higher numer of pretors my e responsile for this erlier eline. A onsierle erese in pe yiel performne is srile to phi feeing injuries on flowers n pos (Miteki n Lm, 1985). An erlier eline in pe phi olonies t the en of pe flowering n thus e ssume to prevent yiel losses in pes. In ontrst to the finings for the semi-lefless ultivr Jmes, simultneous eline of pe phis ws oserve in EFB-tritile interrops n EFB sole rops (Figure 2A, E). This ft might e ttriute to the more open nopy in the semi-lefless winter pe ultivr Jmes, whih offers less protetion from pretors. 4.3 Pe moth infesttion The pe moth infesttion level is epenent on wether onitions n the oiniene etween pe moth flying perio n suseptile plnt growth stges (Huusel-Veistol n Juhiinen, 2006). Thöming n Suke (2012) reporte tht mte pe moth femles prefer the flowering n the lte u stge in pe. Previous stuies hve inite tht the ultivtion of erly-flowering n mturing pes vois or reues this temporl oiniene n therefore the risk of high pe moth infesttion (Shultz n Suke, 2005; Thöming et l., 2011; vn Emen n Servie, 2004). The proportion of pe moth mge pes ws signifintly higher for winter pe ultivr EFB thn for Jmes, inepenent of the rop stn (Tle 10). This ft might e ttriute to the erlier time of flowering n mturity in Jmes thn in EFB. The flowering stge in EFB strte t the en of My in oth experimentl yers, wheres flowering in Jmes ws elye y two weeks in 2010/11. This explins the similr infesttion levels in EFB in oth experimentl yers n the higher pe moth mges of ultivr Jmes in 2010/11. Interropping winter pes n tritile h no effet on the pe moth mge level in 2009/10 (Tle 10). On the ontrry, oth winter pe-tritile interrops were foun to hve signifintly higher proportion of mge pes thn the orresponing sole rops. We might suppose the iffering tul interropping omposition with pe ominte interrop in the first n tritile ominte interrop in the seon experimentl yer to e responsile for this ifferene. Our results re onsistent with Wnuk (1998), who foun no enefiil effet of interropping spring pes n pheli (Pheli tnetifoli Benth.) or white mustr (Sinpis l L.) with regr to pe moth mges on pos. 5 Conlusions Interropping norml-lefe or semi-lefless winter pes n tritile shows gret promise in reuing n infesttion with nnul wees n pe phis. A erese in pe moth mges oul, however, not e hieve y interropping winter pes n tritile. The wee suppressive ility ws signifintly higher with norml-lefe winter pe EFB thn with semi-lefless ultivr Jmes. Pe pest ourrene n infesttion levels were highly epenent on pe flowering time. As result, the erly-flowering winter pe ultivr Jmes h istint vntge over the lter-flowering winter pe v. EFB. Future stuies re neee to seprte the flowering time from the lef type effet with regr to pe phi infesttion. Moreover, it is neessry to evlute the reltionship etween pe nitrogen sttus, phloem sp onentrtion s well s omposition n pe phi infesttion in sole n interroppe pes uner fiel onitions. The ploughing system i not ffet the nnul wee infesttion either in sole or in interrops. On the sis of these results, we onlue tht shllow n eep ploughing re therefore oth fesile in the ultivtion of orgni winter pe n tritile sole or interrops with respet to nnul wees. Whole rop rottions will hve to e exmine in orer to efine the long-term effet of reution in ploughing epth with regr to n infesttion with nnul n perennil wees. 6 Aknowlegements This stuy ws prt of the projet Enhning the eonomi vlue of orgnilly proue sh rops y optimizing the mngement of soil fertility fune y the Germn Feerl Ministry of Foo n Agriulture se on eision of the Germn Bunestg within the frmework of the Feerl Orgni Frming Sheme n other forms of sustinle griulture (BÖLN). We thnk Birte Ivens-Hß n ollegues for their support in the fiel n the Trenthorst Lortory Unit for the hemil nlysis. The uthors express grtitue to Zoel-Sthlu for proviing the skim plough. We lso thnk the Germn Ntionl Meteorologil Servie for the provision of long-term wether t.