Vertical Distribution of Pratylenchus spp. in Silt Loam Soil and Pacific Northwest Dryland Crops

Transcription

1 Vertil Distriution of Prtylenhus spp. in Silt Lom Soil n Pifi Northwest Dryln Crops Rihr W. Smiley, Professor, Json G. Sheey, Fulty Reserh Assistnt, n Snr A. Esley, Fulty Reserh Assistnt, Oregon Stte University, Columi Bsin Agriulturl Reserh Center, P.O. Box 370, Penleton, OR ABSTRACT Smiley, R. W., Sheey, J. G., n Esley, S. A Vertil istriution of Prtylenhus spp. in silt lom soil n Pifi Northwest ryln rops. Plnt Dis. 92: Dryln fiel rops in the Pifi Northwest Unite Sttes re ommonly proue in silt loms infeste y the root-lesion nemtoes Prtylenhus negletus n P. thornei. Soils t 30 sites in Oregon were smple from 0 to 120 m epth to exmine the vertil istriution of these Prtylenhus spp. Both speies were istriute through entire soil profiles of ll ropping systems. Popultions were generlly gretest in the surfe 30 m, ut sometimes high popultions were etete t epths greter thn 45 m. Smpling to 30 m epth llowe etetion of more thn 50 of the popultion in most sites, while smpling to 45 m epth yiele more thn 75 of the popultion in over 75 of the sites evlute. Therefore, soil smples shoul e ollete to 30 to 45 m epth to urtely estimte popultions of Prtylenhus spp. in ryln rops proue on silt loms in the Pifi Northwest. Popultions of Prtylenhus spp. were foun to e relte to the most reently plnte rop, with popultions fter rley, fter whet, n uring summer fllow eing etete in sening orer. Aitionl keywors: hemil fllow, ultivte summer fllow, Horeum vulgre, mustr, Sinpsis l, Tritium estivum The root-lesion nemtoes Prtylenhus negletus (Rensh, 1924) Filipjev & Shuurmnns Stekhoven, 1941 n P. thornei Sher & Allen, 1953 re migrtory root enoprsites tht fee n reproue in the ortex of fiel rops suh s whet (Tritium estivum L.), nol (Brssi npus L.), hikpe (Cier rietinum L.), n rley (Horeum vulgre L.) (3,27,28). These speies penetrte roots n migrte within root tissues y omintion of stylet thrusting n enzymti softening of the host ell wlls (3), using extensive mge to epierml n ortil ells. Reution in rop yiel vries gretly in response to limti n ephi onitions, n to the level of tolerne or intolerne exhiite y iniviul ultivrs n rops (3,19,27,28). P. negletus n P. thornei hve use s muh s 36 reution in whet yiels in Oregon (18,20,21). One or oth speies hve een etete in pproximtely 90 of fiels smple in the Pifi Northwest (PNW) sttes of Iho, Oregon, n Wshington (5,18,22). P. negletus hs een etete more frequently thn P. thornei in these surveys of PNW fiels. Corresponing uthor: R. W. Smiley E-mil: rihr.smiley@oregonstte.eu Aepte for pulition 28 August oi: / PDIS The Amerin Phytopthologil Soiety Representtive smpling of plntprsiti nemtoes is essentil to orrelte yiel loss with nemtoe ensity n to ssess mngement strtegies. Smpling to epth of 20 m is ommonly reommene (11,17) ut smpling to 10 to 20 m epth in Oregon resulte in negtive orreltion of grin yiel with popultion of Prtylenhus spp. (18,20,21) in only hlf the experiments performe. In the other experiments (unpulishe t), yiel improvements from pplition of the nemtiie lir oul not e orrelte with Prtylenhus spp. or ny other orgnism likely to ffet whet yiel n lso e sensitive to lir. Furthermore, pplition of lir to fiel with very low popultion of Prtylenhus spp. i not lter grin yiel (20). Vertil istriution of plnt-prsiti nemtoes is ffete y ftors suh s istriution of host root system, soil temperture n ph, soil type n moisture ontent, vertil migrtion, n mortlity rtes tht vry with soil epth (3,12,14). P. negletus n P. thornei hve een etete s eep s 120 m in Austrli (4,23,25). Tylor n Evns (23) reporte tht smpling to 20 m epth etete more thn 60 of the totl popultion of these speies. Doyle et l. (4) etete greter popultion in the surfe 15 m uring moist yer n t 30 to 60 m epth uring ry yer. Thompson et l. (25) etete less thn 20 of the totl popultion in the top 15 m n mximum popultion ensity t 20 to 30 m epth. Vertil istriutions of Prtylenhus spp. hve not een reporte for the silt loms use to proue most ryln fiel rops in the PNW. The ojetives of this stuy were to: (i) exmine the vertil istriution of Prtylenhus spp. in nonirrigte silt loms in estern Oregon; (ii) etermine whether representtive ropping systems ffet the vertil istriution of Prtylenhus spp.; n (iii) ientify n optimum soil smpling epth to etet popultions of Prtylenhus spp. in the most ommon ropping systems. Fiel-speifi profile istriutions for Prtylenhus spp. re reporte. MATERIALS AND METHODS Smpling proeures. Soil ores were ollete using trtor-mounte Giings GSTRS Hyruli Soil Smpler with 5- m-imeter, 150-m-long slotte soil tue n hevy-uty it (Giings Mhine Compny, Winsor, CO). A pir of soil ores were ollete 1 m prt t eh smpling lotion to ensure suffiient soil ws ollete for eh epth intervl n to minimize the effet of the inherent sptil vriility of Prtylenhus spp. Within eh fiel or experimentl plot, smpling intensity vrie from one lotion per 160 to 360 m 2 in experimentl plots to one lotion per 263 to 638 m 2 in res of interest in ommeril fiels. These smpling intensities exeee the ensity of one lotion per 1,575 m 2 onsiere neessry for effetively hrterizing P. thornei popultions (25). Smpling epths rnge from 45 to 120 m, epening upon the epth to erok or other restritive lyer. Soil ores were seprte into 15-m intervls from 0 to 60 m epth n into 30-m intervls from 60 to 120 m epth. Corresponing intervls from the pir of ores tken from smpling lotion were omposite into smples n store t 4 C until proesse. The Whitehe try metho (29) ws use to extrt nemtoes. Plsti mesh ws ut to size n fitte insie plstiote wire try tht ws then ple into m flt-ottome plsti tu. Two 2-ply fil tissues, slightly overlpping, were li over the plsti mesh. A 200-g susmple from thoroughly mixe soil smple ws spre in 1-m lyer over the tissues. One liter of tp wter ws e to the plsti tu so tht the wter level in the try ws enough to moisten the soil ut not to use wter logging. Nemtoes from 1662 Plnt Disese / Vol. 92 No. 12

2 soil n root segments were ollete in the reservoir of wter. Smples were extrte for 48 h in onstnt-temperture room (22 C), whih woul provie n extrtion effiieny of pproximtely 77 (1). The sket ws then lifte out of the wter n llowe to rin efore the tissue n soil were isre. Wter in the tu ws gitte n poure through 20 µm sieve. The tu ws rinse one n the wter ws psse through the sieve. The sieve ws then rinse twie with miniml wter volume n the suspension ontining nemtoes ws ollete in 30-ml vil. The volume of extrt ws etermine n smples were store t 4 C. Assessments of nemtoe popultions extrte from soil n roots were me using Chlex Corportion (Issquh, WA) gri-style nemtoe-ounting slie, se on the Hwksley slie esign. The queous suspension ws mixe, n 1-ml susmple ws ple on the ounting slie for exmintion t 100 mgnifition. Numers of Prtylenhus spp. were reore n the speies present were etermine y morphometri ssessment (6). Grvimetri soil moisture ontent of eh smple ws etermine y rying 100-g susmple from eh soil smple for 48 h t 105 C. Popultions were expresse s nemtoes per kg of oven-ry soil. Smpling lotions n sites. An erlier soil survey (18) ientifie lotions ner Heppner, Moro, n Penleton, OR suitle for etile stuies of Prtylenhus spp. istriutions in soil profiles. Smpling sites inlue long-term reserh plots (0.05 to 0.2 h) n 0.3- to 1.0-h portions of ommeril fiels with iffering rop histories n tillge mngement. The sites, long with the re smple n numers of smples ollete, re liste in Tle 1. P. negletus ws smple in six plots of long-term experiment (10) t the Center of Sustinility (COS) n in nery ommeril fiels ner Heppner, Morrow County, OR. Preipittion verges 312 mm nnully, nerly ll of whih ours from lte utumn (Otoer) through spring (My). Soil is shllow (45 to 120 m) Vly silt lom; fine-silty, mixe, supertive, mesi Cli Hploxeroll. Smples were ollete from m experimentl plots (COS nos ) on 10 June 2005 n 24 My Tretments in the plots inlue Stephens soft-white winter whet rotte with hemil fllow (COS111; sine 2000), nnul no-till Jefferson hr-re spring whet (COS112; sine 1996), nnul no-till Alpow softwhite spring whet (COS113; sine 1996), nnul no-till Bronesse spring rley (COS114; sine 1996), n oth phses of Stephens winter whet rotte with onventionlly ultivte fllow (COS115, COS116; ontinution of the historil prtie for the region). Eleven ommeril fiels ner Heppner were smple from 2005 to 2007 to omplement omprisons of ropping history n frequeny with COS experimentl fiels. Smples were ollete on 10 June 2005 from Fiel 4 (F4), whih ws plnte to winter whet in Otoer 2004 following 14-month hemil fllow, n plnte to whet nnully from 1999 to On 26 Septemer 2005, smples were ollete from eh of three no-till fiels: (i) the Dle Brown Ro Fiel 1 (DBRF1), whih h een without tillge sine 1996 n ws plnte to Tilney yellow mustr (Sinpsis l L.) in 2005, soft-white spring whet in 2004, winter whet hrveste in 2003, spring rley from 1999 to 2002, spring mustr in 1998, spring rley in 1997, n spring whet in 1996; (ii) O Neill Fiel 1 (ONF1), whih h een mintine without tillge sine 1997 n ws plnte to Bronesse spring rley in 2004 n 2005, to winter whet hrveste in 2003, n mostly to spring rley etween 1997 n 2003; n (iii) Fiel 7 (F7), whih ws hemilly fllowe uring 2005, n plnte to Dirkwin softwhite spring whet uring 2004 n to Stephens winter whet in 2002 n Two ommeril fiels (ONF1 n DBRF1) tht were smple in 2005 were smple gin on 11 My 2006, t ifferent lotions thn in In 2006, fiels ONF1 n DBRF1 ontine stns of Alpow spring whet n Bronesse spring rley, respetively. Also in 2006, smples were ollete on 13 July from two lotions in fiel tht h een mintine s mixe plnting of intermeite whet grss (Thinopyrum intermeium (Host) Brkworth & D.R. Dewey), sheep fesue (Festu ovin L.), n Sierin whet grss (Agropyron frgile (Roth) P. Cnrgy) from out 1988 to In 2006, the soil ws ultivte n the northern hlf (Lierty Shool Ro Fiel North; LSRFN) ws plnte to Dirkwin spring whet n the southern hlf (LSRFS) to Twin spring whet. On 11 My 2007, smples were ollete from Logn Lne Fiels 1 n 2 (LLF1, LLF2), oth of whih were plnte to ORCF-101 winter whet in 2006 n nnul winter whet sine Smples were lso ollete from DBRF1 ontining Belfor spring rley, t ifferent lotion thn smple in 2005 n 2006, n from Dle Tle 1. Summry of smpling lotions, yers, n sites for ssessing istriutions of Prtylenhus spp. in 30 soil profiles in Oregon Smples ollete Lotion Yer Smpling site type (fiel or experiment) n nme Designtion Are (m) Crop No./site Totl Heppner 2005 Experiment: Center of Sustinility, 6 tretments COS SW, WW, SB, SF 5 30 Fiel 4 F WW Dle Brown Ro Fiel 1 DBRF SM 6 6 O Neill Fiel 1 ONF SB Experiment: Center of Sustinility, 6 tretments COS SW, WW, SB, SF 5 30 Dle Brown Ro Fiel 1 DBRF SB 6 6 O Neill Fiel 1 ONF SW Lierty Shool Ro Fiel-North LSRFN MG 9 9 Lierty Shool Ro Fiel-South LSRFS MG Dle Brown Ro Fiel 1 DBRF SW 6 6 Dle Brown Ro Fiel 2 DBRF SM 6 6 Logn Lne Fiel 1 LLF WW 6 6 Logn Lne Fiel 2 LLF WW 6 6 Moro 2006 Four-orners Fiel MSW SW 6 6 Penleton 2005 Fiel B1 B SW Ams Fiel 1 AF WW Ams Fiel 3 AF WW 9 9 Ams Fiel 5 AF WW Ams Fiel 2 AF SW 9 9 Ams Fiel 6 AF WW Eh smple onsiste of omposite of two soil ores ollete 1 m prt, eh of whih ws ivie into 15 to 30 m epth intervls to epth of 120 m. A restritive lyer (slt or lihe) t some lotions n for iniviul smples prevente the olletion of soil ores to the full 120 m epth. Current or most reent rop or tretment on the smpling site (see text for etils): SW = spring whet, WW = winter whet, SB = spring rley, SM = spring mustr, MG = mixe perennil grsses, SF = summer fllow. Plnt Disese / Deemer

3 Brown Ro Fiel 2 (DBRF2), whih h een without tillge sine 1996 n ws plnte to three spring whet n two winter whet rops from 2003 to 2007, spring rley from 1997 to 2002, n winter whet in A fiel t the Columi Bsin Agriulturl Reserh Center ner Moro, Shermn County, OR ws smple for P. negletus. Annul preipittion verges 280 mm, n soil is moertely eep (>120 m) Wll Wll silt lom; orse-silty, mixe, supertive, mesi Typi Hploxeroll. Spring whet h een plnte nnully without tillge sine Smples were ollete on 1 June P. thornei popultions were etermine from smples ollete from six no-till fiels t the Columi Bsin Agriulturl Reserh Center ner Penleton, Umtill County, OR. Annul preipittion verges 400 mm, n soil is vrile epth (60 to 150 m) Wll Wll silt lom. Fiel B1 h ontinuous no-till spring whet ultivrs sine 2002: Alpow from 2002 to 2003 n Zk from 2004 to Ams Fiel 1 (AF1) ws in spring whet in 2002, winter whet uring 2003, hemil fllow in 2004, n Tus soft white winter whet in Ams Fiel 2 (AF2) ws winter whet uring 2003, hemil fllow in 2004, Stephens winter whet in 2005, Zk spring whet in 2006, n hemil fllow in Ams Fiel 3 (AF3) ws in winter whet uring 2003, Alpow spring whet in 2004, hemil fllow in 2005, n Tus winter whet in Ams Fiel 5 (AF5) ws Stephens winter whet uring 2003, Zk spring whet in 2004 n 2005, hemil fllow in 2006, n winter whet vriety tril uring the rop yer. Ams Fiel 6 (AF6) ws winter whet uring 2003, Stephens winter whet in 2004, Zk spring whet in 2005, hemil fllow uring 2006, n Stephens winter whet in Smples were ollete from B1 n AF1 on 27 My 2005, from AF3 n AF5 on 30 My 2006, n from AF2 n AF6 on 10 My Sttistil nlysis. Dt were trnsforme using ln(x + 1) to normlize nemtoe ounts (13) prior to sttistil nlysis. Bk-trnsforme mens re reporte. Fiels smple one or t ifferent sites over 2 or 3 yers were nlyze iniviully using one-wy ANOVA with epth s tretment n smples for loks. Dt were omine prior to nlysis for COS fiels smple in oth 2005 n Cumultive nemtoe popultion perentge through the soil profile ross ll sites n yers ws nlyze with epth s tretment n sites s loks, n with rops s tretment n epths s loks. ANOVA ws performe using CoStt Sttistil Softwre version (CoHort Softwre, Monterey, CA). When tretment mens were signifint t P < 0.05, mens were seprte using the lest signifint ifferene (LSD) test. RESULTS P. negletus n P. thornei were the only speies of Prtylenhus etete in the 30 nonirrigte silt lom sites smple over the 3 yers of this stuy. P. negletus ws the ominnt or only speies etete in fiels ner Heppner n Moro, while P. thornei ws the ominnt or only speies etete in fiels ner Penleton. These speies were istriute throughout the profiles t eh site exmine, n they were etete to 120 m epth in eep soils. When exmine ross sites n yers, smpling the upper 15 m of the soil profile in 30 fiels n experiments le to the etetion of only 32 of the Prtylenhus popultion (Tle 2). Smpling to 30 n 45 m epths yiele 60 n 81 of the popultions, respetively. Similr perentges of etetion t the vrious epths ourre when the results were prtitione mong sites urrently in summer fllow or most reently plnte to spring rley, spring whet, or winter whet. Smpling to 60 m epth ws require to etet 90 of the Prtylenhus spp. popultions in eh of the site tegories. We lso evlute the frequeny t whih vrious proportions of the totl Prtylenhus spp. popultion were etete when ll intervls to 15, 30, or 45 m epth were onsiere. When only the top 0 to 15 m intervl of eh site ws onsiere, very few (10) of the sites h popultion levels tht represente t lest 50 of the totl etetle popultion (t not presente). In ontrst, t lest 50 of the totl etetle popultion ws foun y smpling to 30 n 45 m epth in 63 n 100 of the sites, respetively. Likewise, more thn 70 of the totl etetle popultion ws foun t 30 n 45 m epth in 30 n 70 of the sites, respetively. Although it ws not possile to evlute ifferenes mong ropping systems sttistilly, ifferenes in Prtylenhus spp. popultion n profile istriution were etete mong the smple sites tht ppere to e relte to ropping systems. In experimentl plots ner Heppner with 2- yer rottions of winter whet n summer fllow, popultions of P. negletus within the 15, 30, n 45 m epth intervls were higher uring the fllow phse thn uring the in-rop phse of these rottions (Tle 3), initing n overll eline of popultions uring the 14 months of fllow. More thn 40 of the totl P. negletus popultion ws etete y smpling to 30 m epth in these plots, wheres smpling to only 15 m epth llowe etetion of only 10 to 31 of the popultion. A similr pttern ws foun in fiels ner Penleton with hemil fllow winter whet rottions (Tle 4). Popultions of P. thornei in fiels in summer fllow following winter whet tene to exee those in the winter whet ropping phse. In ll of the fiels, 50 or more of the totl P. thornei popultion ws etete within the top 30 m of the soil profile, n 66 to 82 of the popultion ws e- Tle 2. Prtylenhus spp. popultion with inresing soil epth etermine from ll 30 sites t three lotions in Oregon smple from 2005 to 2007 n from susets of the sites plnte to rop or mnge s summer fllow Soil epth (m) Men All fiels Spring rley Spring whet Winter whet Summer fllow Men 1664 Plnt Disese / Vol. 92 No. 12 Men Men Men , , , , , , , , , , , , , , , , P > F < <0.001 LSD ,213 ns 2,435 2,110 2,610 CV () n Numer of nemtoes per kg of soil; vlues presente re k-trnsforme mens. Perentge of the totl popultion foun in the inite soil epth intervl. Cumultive perentge of the totl popultion from soil surfe to the inite soil epth intervl. Dt points use in the nlysis; e.g., (smples/fiel epth intervls) (missing smples ue to restritive lyer).

4 tete in smples ollete to 45 m epth. In ontrst, shllow (15 m) smplings yiele only 12 to 41 of the popultion. Popultions of P. thornei exeeing 10,000 per kg were etete in the 0 to 15 m intervls from some of the iniviul smples ollete in fiels AF1 n AF5, oth of whih ontine winter whet (t not shown). In 2 yers smpling of experimentl plots ner Heppner with ifferent ontinuous ropping systems, plots roppe with whet h muh higher popultions of P. negletus ompre to the plot ontining rley (Tle 5). Smpling to only 15 m epth yiele highly vrile (14 to 48) proportions of the totl popultion. More thn 50 of the popultion in eh plot ws foun y smpling to 45 m epth. Popultions of P. negletus tene to e higher in plots with winter whet thn with spring whet. These ptterns lso were oserve in nery ommeril fiels. In fiels smple in 2007, higher popultions of P. negletus were etete in fiels with winter whet thn in fiel with spring whet (Tle 6). The potentil for rley to reue P. negletus popultions ws prtiulrly pprent from smpling the DBRF1 fiel ner Heppner over 3 yers (Fig. 1). A very high popultion of P. negletus (up to 10,934 per kg) ws etete throughout the 90-m soil profile following spring mustr rop in When the fiel ws resmple in 2006, following rop of rley, P. negletus popultions t ll epths h erese to very low levels. The P. negletus popultions then inrese when smple gin uring the spring whet rop in Likewise, the O Neil Ro Fiel 1 in 2005, following two suessive rley rops, h P. negletus popultion of 700 per kg of soil t 0 to 30 m epth n 1,426 per kg in the 45 to 60 m epth intervl. The popultions inrese to 972 n 1,444 per kg, respetively, 1 yer lter following the plnting of spring whet (t not shown). Popultions of Prtylenhus spp. were less thn 1,000 per kg of soil in two portions of fiel previously in mixe perennil grsses (LSRFN n LSRFS) n plnte to spring whet (t not shown). Smples ollete to 15 m epth yiele 43 n 72 of the popultions in the two portions of the fiel, while smpling to 30 m epth resulte in etetion of over 96 of the popultion. DISCUSSION P. negletus, P. thornei, or mixtures of these speies were etete throughout the silt lom profiles t 30 nonirrigte sites in Oregon. In eep soils, these Prtylenhus spp. were etete even t the gretest Tle 3. Vertil istriution of Prtylenhus negletus popultions in six soil epth inrements ollete uring 2005 n 2006 from 2-yer rottions of soft white winter whet (SWWW) with either no-till hemil summer fllow (ChemF) or onventionlly ultivte fllow (ConvF) in long-term experiment ner Heppner, OR SWWW ChemF (COS111: 2005) ChemF SWWW (COS111: 2006) SWWW ConvF (COS115: 2005; COS116: 2006) ConvF SWWW (COS116: 2005; COS115: 2006) Soil epth (m) Men Men Men Men , , , , , , , , , , , , , , P > F <0.001 <0.001 <0.001 LSD CV() n e First-liste tretment in eh rottion inites the phse of the rottion smple. Plot esigntion n yer of smpling re in prentheses. COS111 onsiste of two plots with lternting tretments of winter whet n hemil fllow. COS115 n COS116 were offset uplites of rottion of winter whet n onventionlly ultivte summer fllow, llowing nnul smpling of oth phses. Mens (numer of nemtoes per kg of soil) n LSD vlues re k-trnsforme; mens re se on five replite smples t eh epth inrement ollete t eh site uring eh of the 2 yers. Perentge of the totl popultion foun in the inite soil epth intervl. Cumultive perentge of the totl popultion from soil surfe to the inite soil epth intervl. e Dt points use in the nlysis. Tle 4. Vertil istriution of Prtylenhus thornei popultions in soft white winter whet (SWWW) n hemilly fllowe phses of 3-yer no-till rottions t the Columi Bsin Agriulturl Reserh Center ner Penleton, OR Soil epth (m) Men Fiel AF1 (2005) (SWWW) Men Fiel AF3 (2006) (SWWW) Men Fiel AF5 (2006) (hemil fllow) Men Fiel AF6 (2007) (SWWW) Men Fiel AF2 (2007) (hemil fllow) , , , , , , , , , , , , , , , , , P > F <0.001 <0.001 <0.001 <0.001 <0.001 LSD CV() n Mens (numer of nemtoes per kg of soil) n LSD vlues re k-trnsforme; mens for fiels AF1, AF3, AF5, AF6, n AF2 re se on 18, 9, 12, 12, n 18 replites per epth inrement, respetively. Perentge of the totl popultion foun in the inite soil epth intervl. Cumultive perentge of the totl popultion from soil surfe to the inite soil epth intervl. Dt points use in the nlysis. Plnt Disese / Deemer

5 epth smple (120 m), s previously reporte in Austrli (4,25). Smpling to epth of 15 m, s use in erlier surveys of these speies in the PNW (5,18,22) n in ssessments of their impt on whet yiel (20,21), ppers to revel less thn 30 of the totl popultions present in the soil profiles. More thn 50 of the popultions were etete t ll sites y smpling to 30 m epth, n more thn 75 were etete in three-qurters of ll sites smple to 45 m epth. These results inite tht smpling to 15 m epth ws useful for initing presene or sene of these speies, ut not lwys s relile initor of popultions throughout the soil profile. We onlue tht soil smples must e ollete to epth of 30 to 45 m to provie relile estimtes of Prtylenhus spp. popultions in PNW silt loms. Crop history h n importnt influene on totl Prtylenhus spp. popultions s well s soil profile istriutions. Popultions were lower in rop sequenes tht inlue rley thn in rop sequenes with whet grown nnully or in whet fllow rottion. Brley is n effetive rottion rop in Prtylenhus-infeste soil ue to its greter tolerne n resistne to P. thornei n P. negletus (4,7,16,18,24,26). Smiley et l. (18) reporte tht popultions of Prtylenhus spp. were higher in nnully roppe fiels thn in whet fllow rottions, se on smples ollete t 10 to 20 m epth. This stuy emonstrte tht shllow smpling ws responsile for our erlier onlusion tht rop loss ssessment experiments shoul e fouse on fiels roppe nnully (10 of the proution re) rther thn on fiels mnge s whet fllow rottions (90 of proution). We etermine tht proportions of the Prtylenhus spp. popultion reovere in the surfe 15 m t low rinfll sites suh s Heppner n Moro were generlly higher (20 to 48) for nnul fiel rops thn for winter whet summer fllow rottions (13 to Tle 6. Vertil istriution of Prtylenhus negletus popultions in three ommeril whet fiels smple uring 2007 ner Heppner, OR Fiel DBRF2 (spring whet) Fiels LLF1 n LLF2 (winter whet) Soil epth (m) Men Men , , , , , , , , P > F <0.001 LSD CV() 7 21 n e Dt for Fiels LLF1 n LLF2 i not iffer signifintly n were poole. Mens n LSD re k-trnsforme; mens were se on six replites per epth inrement. Perentge of the totl popultion foun in the inite soil epth intervl. Cumultive (from soil surfe to tht soil epth intervl) perentge of the totl popultion. e Dt points use in the nlysis. Fig. 1. Popultion levels of Prtylenhus negletus t ifferent soil epths following spring mustr (SM; smple in 2005), spring rley (SB; smple in 2006), n spring whet (SW; smple in 2007) in nnully roppe, no-till Dle Brown Ro Fiel 1 (DBRF1) ner Heppner, OR. Tle 5. Vertil istriution of Prtylenhus negletus popultions in six soil epth inrements ollete uring 2005 n 2006 from three nnul no-till rop sequenes in long-term experiment ner Heppner, OR Soil epth Annul HRSW (COS112) Annul SWSW (COS113) Annul SB (COS114) (m) Men Men Men , , , , , , P > F <0.001 < LSD CV() n e HRSW = hr re spring whet, SWSW = soft white spring whet, n SB = spring rley. Mens n LSD re k-trnsforme; mens re se on five replites per epth inrement for eh of the 2 yers. Perentge of the totl popultion foun in the inite soil epth intervl. Cumultive perentge of the totl popultion from soil surfe to the inite soil epth intervl. e Dt points use in the nlysis Plnt Disese / Vol. 92 No. 12

6 31). Smpling to 30 or 45 m epth revele little istintion etween popultions in nnul rops n whet fllow rottions. Likewise, the estimte tht 25 of Oregon n Wshington fiels re infeste with potentilly mging popultions of Prtylenhus spp. (18) must now e onsiere highly onservtive. We now estimte tht eonomilly importnt popultions of Prtylenhus spp. (>2,000 per kg of soil) my our in s mny s 60 of PNW ryln fiels. However, it is lso reognize tht Prtylenhus spp. our t very low popultion ensities throughout the soil profiles of whet fllow rottions in some low-rinfll environments suh s Lin, Rlston, n Ritzville, WA (unpulishe t). Although popultions were very low to nonetetle in whet fllow rottions t those three lotions, muh higher popultions ourre throughout the soil profiles of nnul ropping sequenes t the sme lotions, n prtiulrly where n nnul rop ws lso irrigte. Thompson et l. (27) reporte tht Prtylenhus spp. popultions reue y tolernt n resistnt rops inrese to mging levels following s few s two whet rops. We oserve similr response in two fiels ner Heppner, ONF1 n DBRF1. Four suessive rley rops were grown in DBF1 from 1999 to It is likely tht in 2002 the DBRF1 fiel woul hve h low P. negletus popultion similr to those in the ONF1 n COS114 fiels in 2005, whih lso h suessive yers of ropping with rley. Winter whet, spring whet, n mustr were grown on DBF1 uring 2003, 2004, n 2005, respetively, n fter these three suseptile rops, the P. negletus popultion ws very high throughout the 90-m soil profile, n ws prtiulrly high in the surfe 15 m epth intervl. Smiley et l. (21) mesure whet yiel losses up to 40 in fiels with similr P. negletus popultions in the surfe 15 m. Spring rley grown in DBRF1 uring 2006 reue the P. negletus popultion to less thn 1,000 per kg throughout the 90-m soil profile. A single whet rop grown in DBF1 in 2007 inrese the P. negletus popultion in the upper 45 m of soil to level nerly s high s foun following the erlier sequene of two whet n one mustr rop. Although spring rley lerly reue Prtylenhus spp. popultions in nnul ropping systems in Oregon n lso proue greter yiel thn spring whet (35) n winter whet (6 to 29) t Heppner (9), proution of whet is fvore euse it is generlly more profitle thn rley n lso poses less yer-to-yer eonomi risk (8,15). The no-till (hemil fllow) COS111 tretment ner Heppner h higher P. negletus popultions in 2006 thn the onventionlly tille COS115 n COS116 tretments in 2005 n Strusugh et l. (22) lso etete higher popultions of Prtylenhus spp. in reue thn in onventionlly tille ryln ropping systems. In ontrst, Brmež et l. (2) reporte tht tillge i not signifintly reue Prtylenhus spp. popultions, n Smiley et l. (18) foun Prtylenhus popultions to e similr in no-tille n onventionlly tille soils in whet fllow rottions. In view of the high popultions foun in oth ultivte n hemil fllows in this stuy, it is unlikely tht popultion ifferenes ue to tillge, if ny, re of iologil signifine in etermining levels of potentil yiel reution from Prtylenhus spp. Deep smplings of soil profiles shoul e onute to evelop initil fmilirity with the vertil istriution of Prtylenhus spp. in the silt lom profiles of PNW ryln frming systems. An pproprite smpling epth n then e estlishe to ollet n equte proportion of the popultion for use in rop mngement eisions. At the lotions smple in this stuy, smpling to epth of 30 m lwys etete more thn 50 of the totl popultion n ws onsiere equte for most rop mngement eisions. A higher level of etetion (>75) n unerstning of popultion ynmis ws hieve in most (>75) fiels smple to epth of 45 m. ACKNOWLEDGMENTS We grtefully knowlege growers Willim Jepsen n Eugene Logn, n sientist Stephen Mho (Oregon Stte University), for llowing smples to e ollete from their frms n reserh trils. We lso thnk Tin Zekmn, Jonthon Jkson, Alison Thompson, n Deorh Hytt for tehnil ssistne, n Krl Rhinhrt, Erling Josen, n Pul Thorgersen for ssistne with equipment n filities. This reserh ws fune y n OSU suontrt to the USDA- Agriulturl Reserh Servie; SCA# , Control of Root Diseses of Whet n Brley. LITERATURE CITED 1. Bell, N. L., n Wtson, R. N Optimising the Whitehe n Hemming try metho to extrt plnt prsiti n other nemtoes from two soils uner psture. Nemtology 3: Brmež, M., Ivezić, M., n Rspuić, E Effet of mehnil isturnes on nemtoe ommunities in rle ln. Helminthologi 43: Cstillo, P., n Vovls, N Prtylenhus, Nemto, Prtylenhie: Dignosis, iology, pthogeniity n mngement. Nemtol. Monogr. Perspetives 6: Doyle, A. D., MLeo, R. W., Wong, P. T. W., Hetherington, S. E., n Southwell, R. J Eviene for the involvement of the root lesion nemtoe Prtylenhus thornei in whet yiel eline in northern New South Wles. Aust. J. Exp. Agri. 27: Hfez, S. L., Golen, A. M., Rshi, F., n Hnoo, Z Plnt-prsiti nemtoes ssoite with rops in Iho n Estern Oregon. Nemtropi 22: Hnoo, Z. A., n Golen, A. M A key n ignosti ompenium to the speies of the genus Prtylenhus Filipjev, 1936 (Lesion Nemtoes). J. Nemtol. 21(2): Hollwy, G. J., Tylor, S. P., Estwoo, R. F., n Hunt, C. H Effet of fiel rops on popultion ensities of Prtylenhus in southestern Austrli; Prt 2: P. thornei. J. Nemtol. 32: Juergens, L. A., Young, D. L., Shillinger, W. F., n Hinmn, H. R Eonomis of lterntive no-till spring rop rottions in Wshington s whet-fllow region. Agron. J. 96: Mho, S., Petrie, S., Rhinhrt, K., n Qu, A Long-term ontinuous ropping in the Pifi Northwest: Tillge n fertilizer effets on winter whet, spring whet, n spring rley proution. Soil Till. Res. 94: Mho, S., Prithett, L., Josen, E., Petrie, S., Smiley, R., Bll, D., Wysoki, D., Wuest, S., Gollny, H., n Jepsen, W Longterm experiments t CBARC-Moro n Center of Sustinility, Heppner Oregon Agri. Exp. Stn. Spe. Rep. 1068: MSorley, R Extrtion of nemtoes n smpling methos. Pges in: Priniples n Prtie of Nemtoe Control in Crops. R. H. Brown n B. R. Kerry, es. Aemi Press, Syney, Austrli. 12. MSorley, R., n Dikson, D. W Vertil istriution of plnt-prsiti nemtoes in sny soil uner mize. Plnt Soil 123: Protor, J. R., n Mrks, C. F The etermintion of normlising trnsformtions for nemtoe ount t from soil smples n of effiient smpling shemes. Nemtologi 20: Pusini, M. P., Shomker, C. H., Been, T. H., n Moens, M Vertil istriution of the plnt-prsiti nemtoe, Prtylenhus penetrns, uner four fiel rops. Phytopthology 96: Shillinger, W. F., Kenney, A. C., n Young, D. L Eight yers of nnul no-till ropping in Wshington s winter whet-summer fllow region. Agri. Eosyst. Environ. 120: Sheey, J. G., Smiley, R. W., Esley, S. A., n Thompson, A. L Resistne retion of Pifi Northwest spring whet n rley ultivrs to root-lesion nemtoe, Plnt Disese Mngement Reports (online). Report 1:CF022. DOI: /PDMR01. Amerin Phytopthologil Soiety, St. Pul, MN. 17. Shurtleff, M. C., n Averre, C. W., III Dignosing Plnt Diseses use y Nemtoes. Amerin Phytopthologil Soiety, St. Pul, MN. 18. Smiley, R. W., Merrifiel, K., Ptterson, L.-M., Whittker, R. G., Gourlie, J. A., n Esley, S. A Nemtoes in ryln fiel rops in the semiri Pifi Northwest Unite Sttes. J. Nemtol. 36: Smiley, R. W., n Niol, J. M Nemtoes whih hllenge glol whet proution. In: Whet: Siene n Tre. B. F. Crver, e. Blkwell Pulishing, Ames, IA. In press. 20. Smiley, R. W., Whittker, R. G., Gourlie, J. A., n Esley, S. A Prtylenhus thornei ssoite with reue whet yiel in Oregon. J. Nemtol. 37: Smiley, R. W., Whittker, R. G., Gourlie, J. A., n Esley, S. A Suppression of whet growth n yiel y Prtylenhus negletus in the Pifi Northwest. Plnt Dis. 89: Strusugh, C. A., Brley, C. A., Koehn, A. C., n Forster, R. L Survey of root iseses of whet n rley in southestern Iho. Cn. J. Plnt Pthol. 26: Tylor, S. P., n Evns, M. L Vertil n horizontl istriution of n soil smpling for root lesion nemtoes (Prtylenhus negletus n P. thornei) in South Austrli. Austrls. Plnt Pthol. 27: Tylor, S. P., Hollwy, G. J., n Hunt, C. H Effet of fiel rops on popultion en- Plnt Disese / Deemer

7 sities of Prtylenhus negletus n P. thornei in southestern Austrli; Prt 1: P. negletus. J. Nemtol. 32: Thompson, J. P., Brennn, P. S., Clewett, T. G., Sheey, J. G., n Seymour, N. P Progress in reeing whet for tolerne n resistne to root-lesion nemtoe (Prtylenhus thornei). Austrls. Plnt Pthol. 28: Thompson, J. P., Mkenzie, J., n Amos, R Root-lesion nemtoe (Prtylenhus thornei) limits response of whet ut not rley to store soil moisture in the Hermitge long-term tillge experiment. Aust. J. Exp. Agri. 35: Thompson, J. P., Owen, K. J., Stirling, G. R., n Bell, M. J Root lesion nemtoes (Prtylenhus thornei n P. negletus): Progress in mnging signifint pest of grin rops in northern Austrli. Austrls. Plnt Pthol. 37: Vnstone, V. A., Hollwy, G. J., n Stirling, G. R Mnging nemtoe pests in the southern n western regions of the Austrlin erel inustry: Continuing progress in hllenging environment. Austrls. Plnt Pthol. 37: Whitehe, A. G., n Hemming, J. R A omprison of some quntittive methos of extrting smll vermiform nemtoes from soil. Ann. Appl. Biol. 55: Plnt Disese / Vol. 92 No. 12