Rattail Fescue (Vulpia myuros) Control in Chemical-Fallow Cropping Systems

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1 Weed Technology : Rttil Fescue (Vulpi myuros) Control in Chemicl-Fllow Cropping Systems Eric D. Jemmett, Donld C. Thill, Trci A. Ruch, Dniel A. Bll, Sndr M. Frost, Lrry H. Bennett, Joseph P. Yenish, nd Rodney J. Rood* Rttil fescue infesttions re incresing in drylnd conservtion-tillge winter whet cropping systems in the inlnd Pcific Northwest (PNW) region of Idho, Oregon, nd Wshington. Rttil fescue typiclly is controlled with cultivtion in conventionl tillge frming systems. However, reduced soil disturnce hs llowed infesttions to increse significntly. The ojectives of this reserch were to determine the effectiveness of glyphoste rtes nd ppliction timings on control of rttil fescue during chemicl-fllow period in winter whet cropping systems. Chemicl-fllow field studies were conducted during two growing sesons t nine sites throughout the PNW. Glyphoste ws pplied erly POST, lte POST, or sequentilly in erly plus lte POST timings. Additionlly, prqut + diuron ws pplied erly nd lte POST lone or sequentilly with glyphoste. Sequentil ppliction tretments (glyphoste followed y [f ] glyphoste, prqut + diuron f glyphoste, nd glyphoste f prqut + diuron) controlled rttil fescue (, 94% in Idho nd Wshington,, 74% in Oregon) nd reduced pnicle numer (, 85% in Idho,, 30% in Oregon nd Wshington) equivlent to or greter thn one-time tretments. Rttil fescue control nd pnicle reduction generlly incresed with incresing rtes of glyphoste within ppliction timings. Prqut + diuron usully provided similr control nd reduced rttil fescue pnicle numer compred to glyphoste tretments pplied t the sme ppliction timing. Although not completely effective, sequentil pplictions of either glyphoste or prqut + diuron, f glyphoste will provide effective control during chemicl fllow. Nomenclture: Diuron; glyphoste; prqut; rttil fescue, Vulpi myuros L.; winter whet, Triticum estivum L. Key words: Conservtion tillge, direct seed, growth stge, fllow, hericide, no-till. Rttil fescue is reltively new weed prolem infesting conservtion-tillge drylnd winter whet production systems in the inlnd PNW region of Idho, Oregon, nd Wshington. Rttil fescue trditionlly hs een controlled in conventionl tillge systems with intensive tillge prctices during seeded preprtion. However, incresed wreness of the finncil nd environmentl impcts of intense tillge prctices (i.e., soil erosion, inefficient wter conservtion, nd consumption of fossil fuels) hs resulted in incresed doption of no-till, reduced-tillge, or conservtion-tillge prctices (Unger et l. 1971; Veseth 1988). Although conservtiontillge prctices cn reduce soil erosion nd improve soil moisture retention y mintining crop residue cover on the soil surfce (Durhm 2003; Locke 2002), eliminting some or ll tillge cn impct weed mngement ecuse weeds trditionlly controlled with tillge, such s rttil fescue, must e controlled using other methods. Rttil fescue is winter nnul grss elieved to hve een introduced from Europe; however, the specific loction nd time of introduction were not recorded (Hitchcock 1951; Whitson 2000). Rttil fescue ws previously ssigned to the genus Festuc efore eing chnged to Vulpi nd it hs severl different common nmes, which include rttil fescue, foxtil fescue, nd silver grss (Dillon nd Forcell 1984). Rttil fescue is considered n invsive species to the western DOI: /WT * First, second, nd third uthors: Grdute Reserch Assistnt, Professor, nd Reserch Support Scientist II, Deprtment of Plnt, Soil nd Entomologicl Sciences, University of Idho, Moscow ID ; fourth, fifth, nd sixth uthors: Professor nd Fculty Reserch Assistnts, Columi Bsin Agriculturl Reserch Center, Oregon Stte University Pendleton, OR 97801; seventh nd eighth uthors: Extension Specilist nd Agriculturl Reserch Technicin III, Deprtment of Crop nd Soil Science, Wshington Stte University, Pullmn, WA Corresponding uthor s E-mil: jemm3495@uidho.edu flor of the United Sttes ecuse it estlishes quickly in distured res nd hs the ility to compete with ntive plnts (USDA NRCS 2005). Active rttil fescue germintion nd growth cn occur in the fll, winter, nd spring nd the plnt cn quickly rech 0.5 m in height, form thick tufts, nd flower from My to July (Hitchcock 1951; USDA NRCS 2005). Rttil fescue plnts hve een oserved growing in winter whet stnds closely mimicking the growth pttern of whet from seedling emergence to seed mturity (Forcell 1984). Rttil fescue plnt residues rek down slowly nd ccumulte s dense mts on the soil surfce, which cn restrict estlishment of other plnt species. Plnt residue extrcts from this weed cn e llelopthic to whet, dversely ffecting whet rdicle elongtion nd coleoptile growth (An et l. 1997). Persistence of this weed in the field from yer to yer is dependent on weed seed production, the quntity of residue eing crried over on the soil surfce from one seson to the next, seed dormncy, nd the sence or presence of tillge or prepred seededs (An et l. 1997; Dowling 1996; Forcell 1984). It is common weed prolem in pstures nd rngelnd nd is considered low-vlue psture nd rngelnd forge ecuse it hs low winter production nd is unpltle to livestock during spring nd summer growth periods (An et l. 1997; Dowling 1996). Rttil fescue competes with nturl or estlished forge plnt popultions, nd its seed heds injure livestock nd contminte wool (Leys et l. 1991). Selective nd nonselective hericides re used to control weeds in plce of tillge during chemicl-fllow periods (Irelnd 2003). Glyphoste, prqut, prqut + diuron, 2,4- D, chlorsulfuron, nd dicm re commonly used hericides for chemicl fllow (Moyer et l. 1994). Hericide selection depends, in prt, on rottionl crop plnting restrictions nd Jemmett et l.: Rttil fescue control in chemicl-fllow systems N 435

2 weed species. Glyphoste nd prqut + diuron re commonly used in winter whet chemicl-fllow cropping systems ecuse they effectively control weeds nd volunteer crops nd re ffordle. The ojective of this reserch ws to determine optimum glyphoste rtes nd glyphoste nd prqut + diuron ppliction timings for chemicl-fllow control of rttil fescue in drylnd conservtion-tillge winter whet cropping systems in the inlnd PNW region of Idho, Oregon, nd Wshington. Mterils nd Methods Field experiments were estlished t five loctions in drylnd whet growing regions of the inlnd PNW during fll 2003 nd Idho experiments were estlished oth yers ner Moscow t the University of Idho Prker Reserch Frm, nd ner Genesee t the University of Idho Kmitsch Reserch Frm. These sites were pproximtely 16 km prt. To otin uniform weed popultion, rttil fescue ws seeded t Genesee on Octoer 17, 2003, nd Octoer 4, 2004, nd t Moscow on Octoer 20, 2003, nd Octoer 7, 2004, into winter whet stule, which hd een chisel plowed nd disked prior to seeding. In 2003, rttil fescue ws seeded t 17.9 kg/h with 1.2-m doule-disk cone seeder drill equipped with openers spced 16.2 cm prt. Every other seed tue ws pulled to rodcst pproximtely one-hlf of the seed on the soil surfce. However, in 2004, nother 17.9 kg/h of seed ws rodcst seeded onto the soil surfce in the opposite direction s the drilled seed with 1.2-m-wide rolling grss seed nd fertilizer spreder to enhnce the low rttil fescue popultion densities encountered in A rolling hrrow ws used to cover surfce seeds nd compct the soil fter seeding. Oregon experiments were estlished in stnding winter whet stule ner Pendleton t the Columi Bsin Agriculturl Reserch Center nd ner Mission in commercil field; the sites were pproximtely 9 km prt. At Pendleton, rttil fescue seed ws surfce rodcsted with drop spreder on Novemer 4, 2003, nd Septemer 27, 2004, t 24.7 kg/h to ugment sprse nturl popultion. A hevy nturl infesttion ws present t the Mission site oth yers. An experiment lso ws estlished during the fll of 2003 ner Pullmn, Wshington, t the Plouse Conservtion Field Sttion in stnding winter whet stule with nturl rttil fescue infesttion. The experimentl design ws rndomized complete lock with four replictions t ll loctions ech yer. Plots were 2.4 y 9.1 m in the Idho experiments, 2.7 y 9.1 m in Oregon, nd 3.1 y 10.7 m in Wshington. All hericide tretments were pplied in the spring of 2004 nd 2005 using CO 2 - pressurized ckpck spryers. See Tles 1 nd 2 for pplictions dtes nd conditions nd soil informtion t ll loctions. At ll three loctions spryers were clirted to deliver 94 L/h; however, pressure ws 235, 207, nd 221 kp t Idho, Oregon, nd Wshington, respectively. Glyphoste tretments were pplied with mmonium sulfte t 10 g/l nd prqut + diuron tretments were pplied with nonionic surfctnt. 1 Tle 1. Appliction conditions nd soil prmeters for rttil fescue control in chemicl-fllow experiments, 2003 to Experiment sites Moscow, ID Genesee, ID Pendleton, OR Mission, OR Pullmn, WA April 7, 2004 April 26, 2004 Appliction dtes April 22, 2004 My 3, 2004 April 29, 2004 My 10, 2004 Mrch 29, 2004 April 30, 2004 Mrch 29, 2004 April 19, 2004 Appliction timing EPOST LPOST EPOST LPOST EPOST LPOST EPOST LPOST EPOST LPOST 7-cm hed 5 cm 7 10 cm four- to seven-lef two-to three-tiller three- to five-lef seven- to ten-tiller two- to five-tiller three- to five-tiller Rttil fescue growth stge one- to three-tiller Pnicle density/m ,704 2,731 4, Air temperture (C) Reltive humidity (%) Wind (km/h) Cloud cover (%) Soil temperture (C) ph OM (%) CEC (meg/100 g) Soil clssifiction Plouse Plouse Wll Wll Wll Wll Nff Texture silt lom silt lom silt lom silt lom silt lom Arevitions: EPOST, erly POST; LPOST, lte POST; OM, orgnic mtter; CEC, ction exchnge cpcity. 436 N Weed Technology 22, July Septemer 2008

3 Tle 2. Appliction conditions nd soil prmeters for rttil fescue control in chemicl-fllow experiments; 2004 to Experiment sites Moscow, ID Genesee, ID Pendleton, OR Mission, OR Appliction dtes Mrch 3, 2005 April 15, 2005 Mrch 3, 2005 April 18, 2005 Mrch 21, 2005 April 20, 2005 Mrch 21, 2005 April 20, 2005 Appliction timing EPOST LPOST EPOST LPOST EPOST LPOST EPOST LPOST Rttil fescue growth stge one- to three-tiller six- to eight-tiller two- to five-tiller seven- to ten-tiller cm 5 10 cm cm 5 12 cm pnicle density/m 2 5,036 4,938 1,331 3,027 Air temperture (C) Reltive humidity (%) Wind (km/h) Cloud cover (%) Soil temperture (C) ph OM (%) CEC (meg/100 g) Soil clssifiction Plouse Plouse Wll Wll Wll Wll Texture silt lom silt lom silt lom silt lom Arevitions: EPOST, erly POST; LPOST, lte POST; OM, orgnic mtter; CEC, ction exchnge cpcity. Glyphoste 2 tretments were pplied erly POST (EPOST), lte POST (LPOST) (Tles 1 nd 2), nd s sequentil EPOST nd LPOST tretments t 0.42, 0.63, 0.84, nd 1.05 kg e/h (Tle 3). Prqut + diuron 3 (0.56 kg i/h kg i/h) tretments were pplied t 0.84 kg i/h EPOST, LPOST, nd s sequentil EPOST nd LPOST tretments in comintion with glyphoste. Weed control ws evluted visully fter the LPOST ppliction timing using scle from 0 (no control) to 100% (complete control) t 24 to 42 d fter tretment (DAT) t the Idho loctions nd 30 to 34 DAT t the Oregon loctions oth yers, nd 18 DAT t the Wshington loction in At mturity in June (54 to 70 DAT) t the Oregon experiments, nd in July t the Idho (65 to 87 DAT) nd Wshington (73 DAT) experiments rttil fescue plnts were collected from three rndomly plced 625-cm 2 qudrts in ech plot nd comined into single smple, fter which the totl numer of pnicles ws counted. All dt were nlyzed using PROC GLM nd ANOVA. Prior to nlyses, hericide-treted rttil fescue pnicle numer/m 2 were converted to percentge of untreted control pnicle numer/m 2 representing pnicle numer reduction. PROC UNIVARIATE ws used to determine whether or not dt trnsformtion ws needed. Percentge of control s visully evluted nd pnicle reduction mens were seprted using Fisher s Protected LSD test. Tretment mens nd LSMEANS were used to test for significnt interctions nd error significnce when dt were comined over loctions nd yers, nd significnt interctions were plotted nd evluted to determine the cuse nd mgnitude of interctions ( Jemmett 2006). Preplnned single degree of freedom contrsts were used to compre rttil fescue control nd pnicle reduction y EPOST, LPOST, nd sequentil pplictions of glyphoste verged over ll rtes within ech ppliction timing nd to compre EPOST nd LPOST glyphoste nd prqut + diuron pplictions s well s sequentil glyphoste f glyphoste nd prqut + diuron f glyphoste tretments (Tle 4). All computtions were crried out using SAS version 9.1. Results nd Discussion Initil nlyses of the dt indicted tht there ws significnt tretment y loction nd yer interction for ll experiment loctions within stte (P, ) nd lso when comined over ll sttes (dt not shown). Tretment mens were plotted to show where the interctions occurred nd if they would ffect tretment rnkings (dt not shown). Plots of the interction mens indicted tht tretment interctions were miniml nd trends were not ffected if tretments were pooled y sttes over loctions nd yers. Interctions significnt over ll experiment sites were ttriuted to the timing trnsition from EPOST to LPOST to sequentil ppliction tretments. Interctions occurring when dt were comined over yers were ttriuted to the order of mgnitude chnges cused y climtic vritions etween the two growing sesons ( Jemmett 2006). Idho Experiments. Hericide tretment y ppliction timings ws significnt for ll prmeters mesured (dt Jemmett et l.: Rttil fescue control in chemicl-fllow systems N 437

4 Tle 3. Rttil fescue control in chemicl-fllow experiments t four study sites in Idho, four study sites in Oregon, nd one study site in Wshington during 2003 to 2004 nd 2004 to 2005 growing sesons. Appliction ID OR WA Tretment Rte Timing c d d 2004 kg e/h % Gly e 0.42 EPOST Gly 0.63 EPOST Gly 0.84 EPOST Gly 1.05 EPOST Prqut + diuron 0.84 EPOST Gly 0.42 LPOST Gly 0.63 LPOST Gly 0.84 LPOST Gly 1.05 LPOST Prqut + diuron 0.84 LPOST Gly f gly 0.42 f 0.42 EPOST f LPOST Gly f gly 0.63 f 0.42 EPOST f LPOST Gly f gly 0.42 f 0.63 EPOST f LPOST Gly f gly 0.63 f 0.63 EPOST f LPOST Gly f gly 0.63 f 0.84 EPOST f LPOST Gly f prqut + diuron 0.42 f 0.84 EPOST f LPOST Prqut + diuron f gly 0.84 f 0.42 EPOST f LPOST LSD (0.05) Glyphoste pplied with mmonium sulfte t 10 g/l. Prqut + diuron ws pplied with nonionic surfctnt t 0.25% v/v. Product formultions: glyphoste 5 Roundup UltrMxH nd prqut + diuron 5 SurefireH, 2:1 rtio respectively, thus 0.84 kg/h nd 0.28 kg/h, respectively. Glyphoste in kg e/h, prqut + diuron in kg i/h. Spry volume 5 94 L/h. c For erly POST (EPOST) nd lte POST (LPOST) stge of growth see Tles 1 nd 2. d Dt re comined over 2 yr. e Arevitions: gly, glyphoste; EPOST, erly POST; LPOST, lte POST; f, followed y. not shown). Interction plots of the Idho dt showed tht LPOST tretments t Moscow in 2004 visily controlled rttil fescue etter thn LPOST tretments t Moscow in 2005 nd Genesee in 2004 nd 2005 ( Jemmett 2006), nd comined over sites within yers, 2004 LPOST tretments controlled rttil fescue more thn the sme tretments pplied in All sequentilly pplied glyphoste tretments visily controlled rttil fescue 92 to 97%, wheres EPOST glyphoste tretments provided 75 to 92% control nd LPOST tretments controlled rttil fescue 45 to 64% (Tle 3). Weed control with glyphoste pplied EPOST or LPOST generlly incresed with incresing rtes of glyphoste within ech ppliction timing. Prqut + diuron pplied EPOST controlled rttil fescue 83%, wheres control with the LPOST ppliction ws less, t 72%. The two highest glyphoste rtes pplied EPOST controlled rttil fescue etter thn prqut + diuron pplied t the sme time. In contrst, control with prqut + diuron pplied LPOST ws greter thn control with ll LPOST glyphoste tretments ut significntly less thn the EPOST prqut + diuron tretment. Appliction timing contrsts verged over glyphoste rtes showed tht EPOST tretments controlled rttil fescue 87% nd this control ws etter thn the 55% control y LPOST tretments, wheres control y sequentil pplictions of glyphoste verged over ll rtes ws Tle 4. Single degree of freedom contrsts compring visully evluted percentge of rttil fescue control nd pnicle numer reduction ppliction timing mens in chemicl-fllow experiments in four experiments in Idho, four experiments in Oregon, nd one experiment in Wshington, comined over the 2003 to 2004 nd 2004 to 2005 growing sesons. Visully evluted % control % Pnicle reduction Contrsts, ID OR WA ID OR WA P vlue Gly EPOST vs. Prqut + diuron EPOST Gly LPOST vs. Prqut + diuron LPOST, Gly f gly vs. Prqut+diuron f gly Gly EPOST vs. Gly LPOST,.0001,.0001,.0001,.0001,.0001,.0001 Gly EPOST vs. Gly f gly,.0001, ,.0001, Gly LPOST vs. Gly f gly,.0001,.0001,.0001,.0001, Arevitions: gly, glyphoste; EPOST, erly POST; LPOST, lte POST; f, followed y. Glyphoste EPOST or LPOST represents n verge of ll rtes pplied EPOST or LPOST; glyphoste f glyphoste represents n verge of ll rtes pplied EPOST followed y ll rtes pplied LPOST; prqut + diuron f glyphoste represents n verge of the EPOST prqut+diuron f LPOST glyphoste nd EPOST glyphoste f LPOST glyphoste tretments. DF N Weed Technology 22, July Septemer 2008

5 Tle 5. Timing mens for visully evluted percentge of control nd pnicle reduction for rttil fescue control in chemicl-fllow experiments t four study sites in Idho, four study sites in Oregon, nd one study site in Wshington during 2003 to 2004 nd 2004 to 2005 growing sesons. Visully evluted control Pnicle reduction Timing, ID OR WA ID OR WA % Glyphoste (gly) EPOST Gly LPOST Gly EPOST f LPOST Prqut + diuron EPOST Prqut + diuron LPOST Prqut + diuron f gly Arevitions: gly, glyphoste; EPOST, erly POST; LPOST, lte POST; f, followed y. Prqut + diuron f glyphoste were pplied EPOST f LPOST nd LPOST f EPOST. significntly greter, t 96%, thn control y either EPOST or LPOST pplictions (Tles 4 nd 5). Percentge of pnicle reduction of rttil fescue showed little difference over sites within yers for EPOST nd sequentil ppliction tretments, wheres LPOST tretments showed greter vrition in percentge of pnicle reduction ( Jemmett 2006). Percentge of pnicle reduction of rttil fescue ws gretest with LPOST tretments t the Moscow site in 2004 nd t the Genesee site in When dt were pooled over loctions within Idho, percentge of pnicle reduction of rttil fescue ws lwys greter in 2004, t 62 to 100%, thn in 2005, t 19 to 93%, nd these differences were ttriuted to precipittion nd temperture vritions etween the two growing sesons (dt not shown). Novemer 2004 through Ferury 2005 ws drier nd wrmer thn the previous growing seson nd the 30-yr verge. This resulted in rttil fescue plnts reching the pproprite stge for hericide ppliction, one to three tillers, 3 to 4 wk erlier in 2005 compred to However, precipittion ws greter nd men, mximum, nd minimum tempertures tended to e lower in Mrch nd April of 2005 compred to These environmentl conditions my hve reduced the effectiveness of the hericide tretments nd llowed greter plnt recovery following hericide tretment in 2005 thn in Sequentil glyphoste tretments reduced rttil fescue pnicle numer 85 to 96%, wheres EPOST nd LPOST glyphoste pplictions only reduced pnicle numer 47 to 84% nd 42 to 64%, respectively (Tle 6). As with visully evluted percentge of control, pnicle reduction with EPOST nd LPOST tretments generlly incresed with incresing rtes of glyphoste. Prqut + diuron reduced rttil fescue pnicle numer similrly when pplied EPOST (60%) nd LPOST (57%). Similr to visully evluted control, pnicle reduction with the EPOST prqut + diuron tretment ws less thn with the two highest glyphoste rtes pplied EPOST, wheres the LPOST prqut + diuron ppliction reduced pnicle numer s much or more thn the LPOST glyphoste tretments. Pnicle numer reduction ws the gretest with sequentil glyphoste tretments, the highest rte of glyphoste pplied EPOST, nd glyphoste f prqut + diuron pplied sequentilly. Appliction timing contrsts verged over glyphoste rtes showed tht pnicle reduction with the EPOST tretments ws greter, t 69%, compred to LPOST tretments, t 51% (Tles 4 nd 5). Percentge of pnicle reduction with the sequentil glyphoste ppliction timings ws greter, t 90%, thn y oth LPOST nd EPOST glyphoste tretments. Oregon Experiments. Interctions plots of the Oregon dt showed order of mgnitude differences in percentge of rttil fescue control for the EPOST nd sequentil tretments cross ll four experiments (dt not shown). LPOST tretments t Pendleton in 2004 controlled rttil fescue etter thn those t Pendleton in 2005 nd Mission in 2004 nd 2005, wheres control with EPOST tretments ws less thn t Pendleton in 2005 nd Mission in When dt were comined cross loctions within yers, control ws 5 to 25% greter for ll tretments in 2005 compred to Differences in control etween yers were likely cused y climtic differences (dt not shown) s previously explined for the Idho sites. All sequentilly pplied glyphoste tretments visily controlled rttil fescue 68 to 78%, wheres EPOST glyphoste provided 37 to 51% control nd LPOST, 58 to 76% control (Tle 3). Similr to the Idho loctions, control y oth EPOST nd LPOST tretments generlly incresed with incresing glyphoste rtes. The 35% control y EPOST prqut + diuron ws less thn the 63% control y the LPOST ppliction. Rttil fescue control y prqut + diuron pplied EPOST ws less thn control y ll glyphoste rtes except the lowest rte pplied EPOST, wheres control with prqut + diuron pplied LPOST ws not different thn control y the two lowest glyphoste rtes pplied LPOST. Appliction timing contrsts verged over glyphoste rtes showed tht LPOST tretments controlled rttil fescue greter, t 68%, thn EPOST tretments, t 43%, nd control with sequentil pplictions ws greter, t 74%, thn oth LPOST nd EPOST tretments (Tles 4 nd 5). Loction within yer interction plots indicted tht percentge of pnicle reduction of rttil fescue ws greter y LPOST nd sequentil ppliction of glyphoste thn y EPOST pplictions t Pendleton in 2004 wheres the opposite ws true t Mission tht yer (dt not shown). When comined over loctions within yers, percentge of pnicle reduction ws greter in 2005 thn in Sequentil glyphoste tretments reduced rttil fescue pnicle numer 34 to 52%, wheres EPOST nd LPOST pplictions reduced pnicle numer 9 to 23% nd 18 to 40%, respectively (Tle 6). Pnicle reduction with LPOST Jemmett et l.: Rttil fescue control in chemicl-fllow systems N 439

6 Tle 6. Rttil fescue pnicle reduction in chemicl-fllow experiments t 4, 4, nd 1 study sites in Idho, Oregon, nd Wshington, respectively, during 2003 to 2004 nd 2004 to 2005 growing sesons. Appliction ID OR WA Tretment Rte Timing c d d 2004 kg e/h % Gly e 0.42 EPOST Gly 0.63 EPOST Gly 0.84 EPOST Gly 1.05 EPOST Prqut + diuron 0.84 EPOST Gly 0.42 LPOST Gly 0.63 LPOST Gly 0.84 LPOST Gly 1.05 LPOST Prqut + diuron 0.84 LPOST Gly f gly 0.42 f 0.42 EPOST f LPOST Gly f gly 0.63 f 0.42 EPOST f LPOST Gly f gly 0.42 f 0.63 EPOST f LPOST Gly f gly 0.63 f 0.63 EPOST f LPOST Gly f gly 0.63 f 0.84 EPOST f LPOST Gly f prqut + diuron 0.42 f 0.84 EPOST f LPOST Prqut + diuron f gly 0.84 f 0.42 EPOST f LPOST LSD (0.05) Glyphoste pplied with mmonium sulfte t 10 g/l. Prqut + diuron ws pplied with nonionic surfctnt t 0.25% v/v. Product formultions: glyphoste 5 Roundup UltrMxH nd prqut + diuron 5 SurefireH, 2:1 rtio respectively, thus 0.84 kg/h nd 0.28 kg/h, respectively. Glyphoste in kg e/h, prqut + diuron in kg i/h. Spry volume 5 94 L/h. c For erly POST nd lte POST stge of growth see Tles 1 nd 2. d Dt re comined over 2 yr. e Arevitions: gly, glyphoste; EPOST, erly POST; LPOST, lte POST; f, followed y. tretments generlly incresed with incresing rtes of glyphoste. Prqut + diuron pplied EPOST (23%) nd LPOST (35%) reduced pnicle numer eqully. Percentge of pnicle reduction with the EPOST ppliction of the prqut + diuron tretment usully ws not different from EPOST glyphoste tretments, wheres prqut + diuron pplied LPOST ws not different from glyphoste tretments pplied LPOST, except the lowest rte of glyphoste. Appliction timing contrsts verged over glyphoste rtes showed tht percentge of pnicle reduction of rttil fescue with LPOST tretments, t 30%, ws greter thn EPOST tretments, t 15% (Tles 4 nd 5). Percent pnicle reduction with the sequentil glyphoste ppliction timings t 43% ws greter thn oth LPOST nd EPOST glyphoste tretments. Wshington Experiments. Only one Wshington experiment yer nd loction ws included in the study ecuse cceptle popultions of rttil fescue filed to estlish t this loction in 2004 to 2005 growing seson, nd during either growing seson t the second loction. All sequentilly pplied glyphoste tretments controlled rttil fescue 87 to 97%, which ws similr to the 84 to 93% control y EPOST glyphoste tretments ut greter thn the 59 to 71% control y LPOST tretments (Tle 3). Weed control with EPOST tretments generlly incresed percentge of control with incresing rtes of glyphoste. Similr control of rttil fescue occurred with EPOST (75%) nd LPOST (64%) pplictions of prqut + diuron. Rttil fescue control with prqut + diuron pplied EPOST only ws less thn control with the highest glyphoste rte pplied t the sme timing, wheres prqut + diuron nd ll glyphoste rtes pplied LPOST controlled rttil fescue similrly. In contrst to control in Oregon ut somewht similr to control in Idho, rttil fescue control y EPOST pplictions of glyphoste in Wshington verged over glyphoste rtes (88%) ws etter thn the 67% control y the LPOST glyphoste pplictions. Also, the 94% control y sequentil glyphoste pplictions ws greter thn control y LPOST ut not different thn control y EPOST glyphoste pplictions (Tle 4 nd 5). All EPOST nd sequentil tretments in Wshington reduced rttil fescue pnicle numer 13 to 45%, wheres the LPOST tretments only reduced pnicle numer 0 to 7% (Tle 6). As with visul estimtes of control t this loction, the 33% nd 22% pnicle reduction y EPOST pplictions of glyphoste s verged over rte nd the sequentil glyphoste pplictions, respectively, ws similr ut greter thn the 1% reduction y LPOST pplictions (Tles 4 nd 5). In contrst to visul control nd pnicle numer reduction t the other loctions, control nd reduction y the vrious glyphoste rtes pplied either EPOST or LPOST in Wshington ws similr. A rte effect ws mrginl (Tles 3 nd 6). In generl, visully evluted percentge of rttil fescue control nd pnicle numer reduction y EPOST nd LPOST tretments generlly incresed s glyphoste rtes incresed within ech ppliction timing t Idho nd Oregon, ut pnicle reduction ws similr cross rtes within ech timing t Wshington (Tles 3 nd 6). Visully evluted percentge of control ws comprle in ll sttes for the LPOST tretments, rnging from 45 to 76%. However, control with EPOST tretment ws less effective t Oregon, rnging from 35 to 51%, compred to 75 to 93% in Idho nd Wshington. Less control with EPOST 440 N Weed Technology 22, July Septemer 2008

7 pplictions lso reduced control with sequentil tretments in Oregon (71 to 78%) compred to Idho nd Wshington experiments (87 to 97%) (Tle 3). Visile control of rttil fescue in Wshington ws similr to Idho even though Wshington hd nturl infesttions. Although rttil fescue is winter nnul grss, it hs the ility to continue germintion throughout the spring (Hitchcock 1951; USDA NRCS 2005). Germintion nd seedling emergence my still hve een occurring t the Oregon loctions fter the EPOST pplictions, especilly ecuse the rttil fescue stnds there were mostly estlished, nturl infesttions. The dense mts of residue from previous stnds of rttil fescue nd winter whet stule lso my hve cted s physicl rrier preventing hericide interception nd sorption. Plnt residue lso my hve slowed seedling emergence due to colder soil tempertures. Additionl rttil fescue seed ws dded t Pendleton experiments. If rttil fescue seedling emergence continued fter the EPOST pplictions, EPOST would e less effective thn LPOST pplictions. In contrst, little or no emergence proly ws occurring fter the EPOST ppliction timings in Idho nd Wshington, thus providing etter control thn tretments pplied LPOST when the plnts were lrger nd more roust. In fct, the effectiveness of glyphoste nd prqut hs een shown to e dependent on the growth stge of rttil fescue (Forcell 1984; Leys et l. 1991). Percentge of rttil fescue pnicle reduction within stte tended to follow the sme generl trend s visully evluted control, ut ws lwys numericlly less thn or equl to visully evluted control (Tles 3 nd 6). Differences in pnicle reduction compred with visully evluted control my e prtilly relted to differences in when control ws evluted nd when pnicles were collected. Visully evluted control ws ssessed out 1 mo erlier thn when pnicle numers were determined, which my hve llowed rttil fescue to recover nd produce pnicles. Moreover, it ws lso oserved tht some plnts emerged following lte spring rins nd prior to pnicle counts. Additionlly, treted rttil fescue pnicles ppered chlorotic nd this ws included in percentge-of-control rtings. However, pnicle numers usully were not reduced even when the plnts hd these symptoms. Although not completely effective, sequentil pplictions of glyphoste, prqut + diuron f glyphoste, or glyphoste f prqut + diuron provided dequte rttil fescue control during the chemicl-fllow period in conservtion-tillge winter whet cropping systems in the inlnd PNW. Sources of Mterils 1 Nonionic surfctnt, R-11H, Wilur Ellis Co. 345 Cliforni Street, 27th Floor Sn Frncisco, CA Roundup UltrMxH, Monsnto Agriculture Products Co., 800 North Lindergh Boulevrd, St. Louis, MO, SurefireH, 2:1 prqut:diuron mixture from UAP Lovelnd Products, Inc., P.O. Box 1286 Greeley, CO Acknowledgment This reserch ws supported y funding from the Solutions to Economic nd Environmentl Prolems Progrm. Literture Cited An, M., J. E. Prtley, nd T. Hig Phytotoxicity of Vulpi residues: i. investigtion of queous extrcts. J. Chem. Ecol. 23: Dillon, S. P. nd F. Forcell Germintion, emergence, vegettive growth nd flowering of two silvergrsses, Vulpi romoides (L.) S. F. Gry nd V. myuros (L.) C. C. Gmel. Aust. J. Bot. 32: Dowling, P. M The ecology of Vulpi. Plnt Prot. 11: Durhm, S Drought survivl with conservtion tillge. Agric. Res. 51:22. Forcell, F Size structure of silvergrss (Vulpi spp.) popultions in direct drilled whet. Aust. Weeds 3:3 5. Hitchcock, A. S Mnul of the grsses of the United Sttes. Wshington, DC: U.S. Deprtment of Agriculture, Agriculturl Reserch Administrtion Misc. Pul p. [2nd ed. revised y Agnes Chse in two volumes. New York: Dover Pulictions, Inc.]. Irelnd, T. M Vegettion mngement with non-selective hericides during fllow in conservtion tillge, drylnd whet (Triticum estivum) cropping systems in the Pcific Northwest. M.S. thesis. Moscow, ID: University of Idho. Pp Jemmett, E. D The mngement of rttil fescue (Vulpi myuros L.) in winter whet (Triticum estivum L.) cropping systems. M.S. thesis. Moscow, ID: University of Idho. Pp Leys, A. R., B. R. Cullis, nd B. Plter Effect of sprytopping pplictions of prqut nd glyphoste on the nutritive vlue nd regenertion of vulpi [Vulpi romoids (L.) S.F. Grey]. Aust. J. Agric. Res. 42: Locke, M. A., K. N. Reddy, nd R. M. Zlotowicz Weed mngement in conservtion crop production systems. Weed Biol. Mng. 2: Moyer, J. R., E. S. Romn, C. W. Lindwll, nd R. E. Blckshw Weed mngement in conservtion tillle systems for whet production in North nd South Americ. Crop Prot. 13: Unger, P. W., R. R. Allen, nd A. F. Wiese Tillge nd hericides for surfce residue mintennce, weed control, nd wter conservtion. J. Soil Wter Conserv. 26: [USDA NRCS] U.S. Deprtment of Agriculture Nturl Resources Conservtion Service Biology of Vulpi myuros (L). plnt_profile.cgi?symol5vumy#. Accessed: Novemer 11, [USDA NRCS] U.S. Deprtment of Agriculture Nturl Resources Conservtion Service Invsive plnts of the U.S. topics.cgi?erl5invsive_ll.cgi. Accessed: Ferury 28, Veseth, R Conservtion Tillge Considertions for Cerels. pnwsteep.wsu.edu/tillgehndook/chpter2/ htm. Accessed: April 12, Whitson, T. D., ed Weeds of the West. 9th edition. Jckson, WY: Grnd Teton Lithogrphy. Pp Received Ferury 24, 2007, nd pproved April 14, Jemmett et l.: Rttil fescue control in chemicl-fllow systems N 441