Amy E. Hoffner, David L. Jordan, Aman Chandi, Alan C. York, E. James Dunphy, and Wesley J. Everman

Transcription

1 Interntionl Scholrly Reserch Network ISRN Agronomy Volume 2012, Article ID , 7 pges doi: /2012/ Reserch Article Mngement of Plmer Amrnth (Amrnthus plmeri) in Glufosinte-Resistnt Soyben (Glycinemx) with Sequentil Applictions of Herbicides Amy E. Hoffner, Dvid L. Jordn, Amn Chndi, Aln C. York, E. Jmes Dunphy, nd Wesley J. Evermn Deprtment of Crop Science, North Crolin Stte University, P.O. Box 7620, Rleigh, NC , USA Correspondence should be ddressed to Dvid L. Jordn, dvid jordn@ncsu.edu Received 2 October 2012; Accepted 1 November 2012 Acdemic Editors: D. Chikoye, O. Ferrrese-Filho, nd C. Rmsey Copyright 2012 Amy E. Hoffner et l. This is n open ccess rticle distributed under the Cretive Commons Attribution License, which permits unrestricted use, distribution, nd reproduction in ny medium, provided the originl work is properly cited. Plmer mrnth (Amrnthus plmeri S. Wts.) is one of the most difficult weeds to control in soyben (Glycine mx (L.) Merr.) in North Crolin. Reserch ws conducted during 2010 nd 2011 to determine if Plmer mrnth control nd soyben yield were ffected by soyben plnt popultion nd combintions of preemergence (PRE) herbicides followed by single ppliction of glufosinte postemergence (POST) versus multiple pplictions of glufosinte POST. Plmer mrnth ws controlled more, nd soyben yield ws greter when soyben ws estblished t 483,000 plnts h 1 in 3 of 4 experiments compred with soyben t 178,000 plnts h 1 irrespective of herbicide tretments. In seprte experiments, ppliction of PRE herbicides followed by POST ppliction of glufosinte or multiple POST pplictions of glufosinte provided vrible Plmer mrnth control, lthough combintions of PRE nd POST herbicides controlled Plmer mrnth the most nd provided the gretest soyben yield. In 1 of 3 experiments, sequentil pplictions of glufosinte were more effective thn single ppliction. Yield ws higher in 2 of 3 experiments when glufosinte ws pplied irrespective of timing of ppliction when compred with the nontreted control. In the experiment where glufosinte ws pplied t vrious POST timings, multiple pplictions of the herbicide provided the best control nd the gretest yield compred with single pplictions. 1. Introduction Resistnce of Plmer mrnth to cetolctte synthse (ALS-) inhibiting herbicides nd glyphoste is well documented in North Crolin [1 3]. Controlling herbicideresistnt Plmer mrnth cn be chllenging becuse lterntives to glyphoste nd ALS-inhibiting herbicides require timely ppliction [4, 5]. Row pttern nd plnt popultion cn influence weed mngement in soyben [6, 7]. Herbicides tht pplied PRE or POST other thn glyphoste re importnt in mnging glyphoste-resistnt Plmer mrnth in soyben [8 10]. Under weed-free conditions, soyben t popultions below those estblished in mny fields in North Crolin yield s well s soyben t higher popultions considered stndrd (exceeding 300,000 plnts h 1 )(E. J. Dunphy, personl communiction). Estblishing soyben t lower popultions cn reduce production costs if yields re mintined. Results compring the economic vlue of high soyben popultions versus incresing the number of POST herbicides re mixed [11 16]. Additionl reserch is needed to determine if Plmer mrnth control is more effective when soyben is estblished t higher popultions in glufosinte-resistnt soyben. Glufosinte-resistnt soyben llows producers to pply glufosinte to control problemtic weeds like Plmer mrnth [17]. Sequentil progrms, either s PRE followed by POST pplictions or multiple POST pplictions of herbicides, cn be effective in controlling weeds, especilly glyphoste-resistnt Plmer mrnth [18]. Timely pplictions of glufosinte in glufosinte-resistnt soyben cn be effective in controlling glyphoste-resistnt nd glyphostesusceptible Plmer mrnth [17]. Reed et l. [19] reported

2 2 ISRN Agronomy tht multiple pplictions of glufosinte in totl POST herbicide progrm controlled Plmer mrnth effectively. However, most recommendtions by Coopertive Extension Service representtives include sequentil pplictions of PRE herbicides followed by timely POST herbicides, especilly in fields where glyphoste-resistnt Plmer mrnth is suspected. Given tht Plmer mrnth hs become more prevlent in North Crolin, especilly herbicide-resistnt biotypes, reserch is needed to better define the role of seeding rte on weed mngement progrms for soyben. Determining if sequentil pplictions of PRE nd POST herbicides re s effective s multiple POST pplictions of glufosinte lone will be importnt, especilly in terms of response to soyben popultion. Reserch is lso needed to better define the time between multiple pplictions of glufosinte. Therefore, reserch ws conducted in North Crolin to compre Plmer mrnth control nd soyben yield with combintions of PRE nd POST herbicides pplied to glufosinte-resistnt soyben t two soyben popultions nd to determine the most effective timing of multiple POST pplictions of glufosinte. 2. Mterils nd Methods 2.1. Interctions of Plnt Popultion nd Herbicide Progrm. The experiment ws conducted in North Crolin in two seprte fields during ech yer (2010 nd 2011) t the Upper Costl Plin Reserch Sttion locted ner Rocky Mount with nturl nd reltively high popultions of Plmer mrnth. Popultions of weed species other thn Plmer mrnth were low nd inconsistent cross fields compred with density nd distribution of Plmer mrnth. One field consisted of Lynchburg fine sndy lom soil (fine-lomy, siliceous, semictive, thermic, nd Aeric Plequults) while the second field ws Nhunt lom soil (fine-silty, siliceous, thermic, nd Aeric Plequults). Corn (Ze mys L.) nd cotton (Gossypium hirsutum L.) preceded soyben on these respective soil series. Soyben cultivr LL 595 N (Southern Sttes Coopertive, Inc., Frmville, NC 27828, USA) ws plnted between My 24 nd June 7 fter disking nd field cultivtion in rows spced 20 cm prt in plots 12 rows wide by 9 m. Tretments consisted of two levels of soyben popultion (178,000 plnts h 1 versus 483,000 plnts h 1 ) nd four levels of herbicide progrm. Herbicide tretments included glufosinte POST pplied 2 weeks fter plnting (WAP), glufosinte pplied sequentilly 2 nd 4 WAP, S-metolchlor plus fomesfen pplied PRE, nd S-metolchlor plus fomesfen pplied PRE followed by glufosinte POST 4 WAP. A nontreted control lso ws included. S-metolchlor plus fomesfen (Prefix herbicide, Syngent Crop Protection, Greensboro, NC 27709, USA) ws pplied t g e h 1 while glufosinte-mmonium (Ignite 280 herbicide, Byer CropScience, Reserch Tringle Prk, NC 27709) ws pplied t 670 g e h 1.Herbicides were pplied using CO 2 -pressurized bckpck spryer clibrted to deliver 145 L h 1 using 8002 regulr flt-fn nozzles (Teejet Corportion, Wheton, IL 60187, USA) t 275 kp. Plmer mrnth ws 2 to 6 cm in height when glufosinte ws pplied POST. Visible estimtes of percent Plmer mrnth control were recorded 6 WAP using scle of 0 to 100, where 0 is no control nd 100 is complete control. Soyben ws mchine hrvested, nd finl yield ws djusted to 15% moisture. The experimentl design ws rndomized complete block with tretments replicted four times. Dt for Plmer mrnth control nd soyben yield were subjected to ANOVA using the Proc GLM procedure in SAS (SAS Institute, GLM Procedure, Cry, NC 27513, USA) for four (site/yer combintions) by four (herbicide progrm) fctoril rrngement of tretments. The nontreted control ws not included in this nlysis becuse soyben ws not hrvestble when herbicide ws not included. Mens of significnt min effects nd interctions were seprted using Fisher s Protected LSD test t P Efficcy of Sequentil Herbicide Progrms in Single Plnt Popultion. Two experiments were conducted with either sequentil pplictions of PRE followed by POST herbicides or multiple pplictions of glufosinte only. The experiment with sequentil pplictions of PRE nd POST herbicides ws conducted during 2010 nd 2011 t the Upper Costl Plin Reserch Sttion ner Rocky Mount in the fields discussed previously (Nhunt soil series during 2010 nd Lynchburg soil series during 2011). The experiment with multiple pplictions of glufosinte ws conducted during 2010 on Norfolk lom snd soil (fine-lomy, kolinitic, thermic, nd Typic Kndiuldults) nd in two seprte fields during 2011 on both the Nhunt nd Lynchburg soil series described previously. The glufosinte-resistnt soyben cultivr LL 595N (Southern Sttes Coopertive, Inc., Frmville, NC 27828, USA) ws plnted fter disking nd field cultivtion in rows spced 20 cm prt with finl plnt popultion of 480,000 plnts h 1. Plot size ws the sme s described previously. In the experiment with sequentil ppliction of PRE nd POST herbicides, tretments consisted of seven levels of PRE herbicides, including no PRE, flumioxzin (Vlor SX, Vlent USA Corportion, Wlnut Creek, CA 94596, USA) lone t 70 g i h 1 or with chlorimuron (Vlor XLT herbicide, E. I. DuPont de Nemours nd Co., Wilmington, DE 19898, USA) t 21 g i h 1, the sodium slt of fomesfen (Reflex herbicide, Syngent Crop Protection, Greensboro, NC 27709, USA) t 280 g e h 1, S-metolchlor (Dul II Mgnum, Syngent Crop Protection, Greensboro, NC 27709, USA) t 1500 g i h 1, S-metolchlor plus fomesfen (Prefix herbicide, Syngent Crop Protection, Greensboro, NC 27709, USA) t g h 1, nd sulfentrzone plus clornsulm-methyl (Authority First herbicide, FMC Corportion, Phildelphi, PA 19103, USA) t g i h 1, respectively. Ech of these PRE herbicides ws followed by no POST herbicide or single ppliction of glufosinte mmonium (Ignite 280 herbicide, Byer CropScience, Reserch Tringle Prk, NC 27709, USA) t 670 g h 1 2WAPor

3 ISRN Agronomy 3 sequentil pplictions of glufosinte t 400 g h 1 t 2 nd 4 WAP. In the experiment with only POST pplictions of glufosinte, tretments consisted of glufosinte pplied 2 WAP t 400 nd 670 g h 1 (referred to s POST 1) followed by no dditionl pplictions of glufosinte or followed by second ppliction of glufosinte t 400 g h 1 t 3 WAP (referred to s POST 2) or 4 WAP (referred to s POST 3). Tretments lso included three sequentil pplictions of glufosinte t 400 g h 1. Plmer mrnth size rnged from 5 to 10 cm in height when glufosinte ws pplied in the experiment with PRE nd POST herbicides. In the experiment with multiple pplictions of glufosinte only, Plmer mrnth height ws 5 to 10 cm t POST 1, 5 to 20 cm t POST 2, nd 5 to 40 cm t POST 3. The rnge in size of Plmer mrnth reflected differences in emergence of weeds cused by PRE herbicides prior to the POST ppliction in experiment. In both experiments, glufosinte ws pplied using the procedures described previously. Percent Plmer mrnth control ws estimted visully nd ws recorded 10 WAP in both experiments s described previously. Soyben yield ws determined in ech plot nd djusted to finl moisture of 15%. The experimentl design ws rndomized complete block with four replictions. Dt for Plmer mrnth control nd soyben yield were subjected to ANOVA using the Proc GLM procedure in SAS (SAS Institute, Cry, NC 27513, USA) considering the fctoril rrngement of tretments. Mens of significnt min effects nd interctions were seprted using Fisher s Protected LSD test t P Results nd Discussion 3.1. Interctions of Plnt Popultion nd Herbicide Progrm. Interctions of experiment (site/yer combintion) by soyben popultion nd experiment by herbicide progrm were significnt for both Plmer mrnth control (P = nd , resp.) nd soyben yield (P nd , resp.). The interction of experiment by soyben popultion by herbicide progrm ws not significnt for Plmer mrnth control (P = ) nd soyben yield (P = ). Additionlly, the interction of soyben popultion by herbicide progrm ws not significnt for these prmeters (P = nd , resp.). Plmer mrnth ws controlled more effectively when soyben ws estblished t the higher seeding rte by 11 to 13 percentge points t 3 of 4 loctions (Tble 1). At fourth loction control ws numericlly higher by 6 percentge points t the higher plnt popultion. Soyben yield ws higher in 3 of 4 experiments when estblished t the higher popultion (Tble 1). However, there ws some discrepncy in Plmer mrnth control nd soyben yield mong experiments when compring soyben popultion. The reltively low soyben yields on the Nhunt soil series during 2010 due to dry wether most likely minimized the possibility of seprting yields bsed on Plmer mrnth control. The higher soyben yield during 2010 on the Lynchburg soil series or during 2011 on the Nhunt soil series most likely reflected differences in Plmer mrnth control. On the Lynchburg soil series during 2011 there ws slight but nonsttisticl difference in Plmer mrnth control but cler increse in yield t the higher plnt popultion. Other fctors could hve contributed to higher yields t higher soyben popultion tht re not relted to weed control. Considerble vrition in Plmer mrnth control ws noted mong herbicide tretments cross experiments (Tble 2). Control by multiple pplictions of glufosinte exceeded tht of single ppliction of glufosinte in 3 of 4 experiments. Sequentil pplictions of glufosinte only nd S-metolchlor plus fomesfen PRE controlled Plmer mrnth similrly in 3 of 4 experiments. Applying glufosinte following S-metolchlor plus fomesfen ws more effective thns-metolchlor plus fomesfen lone, sequentil pplictions of glufosinte, nd single ppliction of glufosinte in 1, 3, nd 4 experiments, respectively. Soyben yield during 2010 on the Nhunt soil series ws low nd did not differ mong herbicide progrms, most likely becuse yield ws reltively low compred to the Lynchburg soil series during 2010 nd both soil series during 2011 (Tble 2). On the Lynchburg series during 2010, soyben yield ws higher following sequentil pplictions of glufosinte compred with single ppliction; yield with S-metolchlor plus fomesfen lone or followed by glufosinte ws intermedite. On the Nhunt soil series during 2011, soyben yield with the more intensive progrm of S-metolchlor plus fomesfen followed by glufosinte yield exceeded yield following the other herbicide progrms. On the Lynchburg soil series, yield with this progrm lso ws higher thn single ppliction of glufosinte. Although some vrition in Plmer mrnth control nd soyben yield ws noted when compring herbicide progrms, lck of soyben popultion by herbicide progrm interction for these prmeters suggests tht higher soyben popultions will increse Plmer mrnth control nd soyben yield irrespective of herbicide progrm Efficcy of Sequentil Herbicide Progrms in Single Plnt Popultion. The interction of yer by PRE by POST herbicide ws significnt for Plmer mrnth control (P ) nd for soyben yield (P ). Therefore, dt were nlyzed by yer. The interction of PRE by POST ws not significnt for Plmer mrnth control (P = ) but ws significnt for soyben yield (P = ) during However, the interction of PRE by POST herbicides ws significnt for both Plmer mrnth control (P = ) nd soyben yield (P = ). Plmer mrnth control by flumioxzin lone or with chlorimuron ws 93 to 98% while fomesfen lone or with S-metolchlor provided 77 to 80% control (Tble 3). Sulfentrzone plus clornsulm methyl controlled Plmer mrnth 66%, while S-metolchlor provided only 56% control. Whitker et l. [20] found similr results for Plmer mrnth control with flumioxzin nd fomesfen PRE. Plmer mrnth control ws similr when glufosinte ws pplied either once or sequentilly (Tble 3). Lck of difference in single nd sequentil pplictions most likely

4 4 ISRN Agronomy Tble 1: Interction of experiment nd soyben popultion for Plmer mrnth control nd soyben yield. Plmer mrnth control Soyben yield Yer Soil series Soyben plnt popultion b Soyben plnt popultion b Low High Low High % kgh Nhunt Lynchburg Nhunt Lynchburg Indictes significnt difference t P 0.05 within n experiment compring low nd high plnt popultions for Plmer mrnth control nd soyben yield. Dt re pooled over herbicide progrms. b The low soyben popultion ws pproximtely 178,000 plnts h 1. The high soyben plnt popultion ws pproximtely 483,000 plnts h 1. Tble 2: Interction of experiment nd herbicide progrm for Plmer mrnth control nd soyben yield. Plmer mrnth control Soyben yield Soil series Soil series Herbicide progrm Nhunt Lynchburg Nhunt Lynchburg Nhunt Lynchburg Nhunt Lynchburg % kgh 1 Glufosinte 46 c 74 c 81 b 71 c b 2640 c 3840 b Glufosinte followed by glufosinte 62 b b 85 b b 4120 b S-metolchlor plus fomesfen 70 b 93 b b b 3020 bc 4220 b S-metolchlor plus fomesfen followed by glufosinte b b Mens within yer nd field followed by the sme letter re not different ccording to Fisher s Protected LSD test t P Dt re pooled over soyben plnt popultion. reflects limited weed emergence fter the first POST ppliction nd rpid closure of the soyben cnopy. All PRE herbicides incresed soyben yield during 2010 compred with the no-pre herbicide control (Tble 3). Yield of soyben receiving S-metolchlor plus fomesfen exceeded tht of soyben treted with flumioxzin lone, sulfentrzone plus clornsulm methyl, or flumioxzin plus chlorimuron. Surprisingly, yield following single ppliction of glufosinte ws lower thn soyben yield without POST ppliction of glufosinte or soyben receiving multiple pplictions of glufosinte. Severl differences in Plmer mrnth control mong PRE herbicides were observed during 2011, especilly in bsence of glufosinte (Tble 4). Flumioxzin, flumioxzin plus chlorimuron, S-metolchlor plus fomesfen, nd fomesfen lone provided the best control. Sulfentrzone plus clornsulm-methyl nd S-metolchlor lone provided intermedite control between the most effective PRE herbicides nd the nontreted control. When glufosinte ws pplied only once, no difference in control mong PRE herbicides ws observed. There were no significnt differences in soyben yield mong PRE herbicide tretments when glufosinte ws pplied, regrdless of the number of glufosinte pplictions (Tble 5). In the bsence of glufosinte, soyben yield following fomesfen, S-metolchlor, nd sulfentrzone plus clornsulm methyl ws intermedite between the nontreted control nd flumioxzin lone or with chlorimuron or S-metolchlor plus fomesfen. In the second experiment with totl POST pplictions of glufosinte pplied sequentilly 2, 3, nd 4 WAP, the interction of glufosinte rte with sequence of glufosinte ppliction ws not significnt for Plmer mrnth control (P = ) or soyben yield (P = ). Although glufosinte rte s min effect or the interction with yer or sequence of glufosinte ppliction ws not significnt (P 0.05), the interction of experiment by sequence of glufosinte ppliction ws significnt for Plmer mrnth control (P = ) nd soyben yield (P = ). In 2010, multiple pplictions of glufosinte controlled Plmer mrnth 97 to 99% thn single ppliction 82% (Tble 6). In systems with two pplictions, timing of the second ppliction hd no effect on Plmer mrnth control. Also, Plmer mrnth control ws similr with two nd three pplictions. Soyben yield ws not ffected by the number of glufosinte pplictions. However, glufosinte POST incresed yield over nontreted soyben. During 2011, on the Nhunt soil series, Plmer mrnth control ws similr with ll glufosinte pplictions nd ws t lest 97%. In the second field on Lynchburg soil series, control ws greter where glufosinte ws pplied sequentilly compred with single ppliction.

5 ISRN Agronomy 5 Tble 3: Plmer mrnth control nd soyben yield s influenced by min effects of PRE nd POST herbicide tretments during 2010 on the Nhunt soil series. Herbicides Herbicide rte Plmer mrnth control Soyben yield gh 1 % kgh 1 PRE herbicides None 29 e 1150 c Flumioxzin b Sulfentrzone plus clornsulm methyl cd 1450 b S-metolchlor plus fomesfen c 1680 Flumioxzin plus chlorimuron b 1420 b Fomesfen bc 1570 b S-metolchlor d 1500 b POST herbicides None 64 b 1500 Glufosinte b Glufosinte then glufosinte 400 then Menswithintretmentfctor(PREorPOSTherbicides)forechprmeterfollowedbythesmeletterrenotdifferent ccording to Fisher s Protected LSD test t P Dt for PRE herbicides re pooled over levels of POST herbicides. Dt for POST herbicides re pooled over levels of PRE herbicides. Tble 4: Plmer mrnth control s influenced by the interction of PRE nd POST herbicide tretments during 2011 on the Lynchburg soil series. PRE herbicides PRE herbicide rte gh 1 Plmer mrnth control Glufosinte rte (kg h 1 ) then 0.40 % None 0e 88 d 81bcd Flumioxzin bc Sulfentrzone plus clornsulm methyl cd d S-metolchlor plus fomesfen d 96 bc 97 bc Flumioxzin plus chlorimuron bc Fomesfen d b S-metolchlor d 91 d 91 d Mens followed by the sme letter re not different ccording to Fisher s Protected LSD test t P Tble 5: Soyben yield s influenced by the interction of PRE nd POST herbicide tretments during 2011 on the Lynchburg soil series. Soyben yield PRE herbicides PRE herbicide rte Glufosinte rte (kg h 1 ) gh then 0.40 kg h 1 None 1340 e 3800 bc 3850 bc Flumioxzin b 3500 d 3770 d Sulfentrzone plus clornsulm methyl d 3850 bc 3740 d S-metolchlor plus fomesfen d 3550 d 4090 Flumioxzin plus chlorimuron d 4000 b 3870 bc Fomesfen bcd 3890 bc 4240 S-metolchlor cd 3350 d 3530 d Mens followed by the sme letter re not different ccording to Fisher s Protected LSD test t P 0.05.

6 6 ISRN Agronomy Tble 6: Plmer mrnth control nd soyben yield s influenced by the glufosinte rte nd number of pplictions. Plmer mrnth control or soyben yield Glufosinte ppliction timing (WAP) b Nhunt soil series Lynchburg soil series Plmer mrnth control Yes No No 82 b b Yes No Yes Yes Yes No Yes Yes Yes Soyben yield (kg h 1 ) Yes No No b 3030 Yes No Yes b 2990 Yes Yes No Yes Yes Yes b 2530 b No No No 600 b 2780 b 870 c Mens within yer or yer nd soil series combintion for ech prmeter followed by the sme letter re not significntly different ccording to Fisher s Protected LSD test t P Dt re pooled over glufosinte rtes. Dt for the nontreted control were not included in the sttisticl nlyses to llow considertion of fctoril tretment structure. b Norfolk soil series. During 2011, on the Nhunt soil series, soyben receiving single ppliction of glufosinte nd nontreted soyben yielded similrly. Yield ws incresed when second ppliction of glufosinte ws mde 3 WAP (Tble 6). On the Lynchburg series during 2011, soyben yield exceeded tht of the nontreted control when glufosinte ws pplied irrespective of sequence of ppliction. However, soyben yield ws lower with three pplictions of glufosinte compred with two pplictions only. Given Plmer mrnth control ws high with the progrm contining three pplictions, lower yield most likely reflected soyben injury. The totl mount of glufosinte pplied in this tretment exceeds the mnufcturer s recommendtions [21]. 4. Conclusions ThemostconsistentPlmermrnthcontrolwsobtined with multiple pplictions of herbicides either s PRE followed by POST or POST pplictions of glufosinte. Additionlly, timing of glufosinte ws not criticl when two pplictions were mde within the first 4 weeks fter plnting. Concern for overrelince on protoporphyrinogen oxidse (PPO-) inhibiting herbicides nd subsequent development of PPO-resistnt biotypes in fields with glyphosteresistnt Plmer mrnth hs been expressed [9]. Results from this reserch indicte tht while tretments including PPO herbicides controlled Plmer mrnth more effectively when pplied lone for the entire seson, the PRE herbicide tretment with non-ppo mode of ction, in this cse S- metolchlor lone, performed s well in comprehensive progrm including one or two pplictions of glufosinte. While multiple pplictions of glufosinte re currently effective in controlling Plmer mrnth s described here nd from other reserch [17 19], the long-term sequentil ppliction of PRE nd POST herbicides with greter diversity of modes of ction is the best pproch when considering herbicide resistnce mngement. Conflict of Interests None of the uthors hve ny conflict of interests in terms of the products mentioned in the pper. Acknowledgments The North Crolin Soyben Growers Assocition nd Byer CropScience provided prtil funding for this reserch. Apprecition is expressed to Jmie Hinton, Rick Segroves, Dewyne Johnson, Peter Eure, nd stff t the Upper Costl Plin Reserch Sttion for ssistnce with this reserch. References [1] I. Hep, The interntionl survey of herbicide resistnt weeds, 2012, [2]J.R.Whitker,Distribution, biology, nd mngement of glyphoste-resistnt plmer mrnth in North Crolin [PhD disserttion], North Crolin Stte University, [3] A. E. Hoffner, D. L. Jordn, nd A. C. York, Geogrphicl distribution of herbicide resistnce in Plmer mrnth (Amrnthus plmeri) popultions cross North Crolin, in Proceedings of the 7th Interntionl IPM Symposium: IPM on the World Stge, pp , Memphis, Tenn, USA, [4]A.S.Culpepper,A.C.York,A.W.McRe,ndJ.Kichler, Glyphoste-resistnt Plmer mrnth response to weed mngement progrms in Roundup Redy nd Liberty Link Cotton, in Proceedings of the Beltwide Cotton Conferences, Ntionl Cotton Council, Nshville, Tenn, USA, Jnury 2008.

7 ISRN Agronomy 7 [5] L. M. Sosnoskie, J. M. Kichler, R. D. Wllce, nd A. S. Culpepper, Multiple resistnce in Plmer mrnth to glyphoste nd pyrithiobc confirmed in Georgi, Weed Science, vol. 59, no. 3, pp , [6] D. B. Hrder, C. L. Sprgue, nd K. A. Renner, Effect of soyben row width nd popultion on weeds, crop yield, nd economic return, Weed Technology, vol. 21, no. 3, pp , [7]G.T.Plce,S.C.Reberg-Horton,J.E.Dunphy,ndA.N. Smith, Seeding rte effects on weed control nd yield for orgnic soyben production, Weed Technology, vol. 23, no. 4, pp , [8] T. C. Mueller, P. D. Mitchell, B. G. Young, nd A. S. Culpepper, Proctive versus rective mngement of glyphoste-resistnt or -tolernt weeds, Weed Technology, vol. 19, no. 4, pp , [9] M. D. K. Owen, Evolved glyphoste-resistnt weeds nd weed shifts: weed species in glyphoste-resistnt crops, Pest Mngement Science, vol. 64, no. 4, pp , [10] D. R. Shw, M. D. Owen, P. M. Dixon et l., Benchmrk study on glyphoste-resistnt cropping systems in the United Sttes prt 1: introduction to , Pest Mngement Science, vol. 25, pp , [11] D. A. Guillermo, P. Pedersen, nd R. G. Hrtzler, Soyben seeding rte effects on weed mngement, Weed Technology, vol. 23, no. 1, pp , [12] O. W. Howe nd L. R. Oliver, Influence of soyben (Glycine mx) row spcing on pitted morningglory (Ipomoe lcunose) interference, Weed Science, vol. 35, pp , [13] G. R. W. Nice, N. W. Buehring, nd D. R. Shw, Sicklepod (Senn obtusifoli) response to shding, soyben (Glycine mx) row spcing, nd popultion in three mngement systems, Weed Technology, vol. 15, no. 1, pp , [14] J. K. Norsworthy nd J. R. Frederick, Reduced seeding rte for glyphoste-resistnt, drilled soyben on the southestern Costl Plin, Agronomy Journl, vol. 94, no. 6, pp , [15]J.K.NorsworthyndL.R.Oliver, Effect of seeding rte of drilled glyphoste resistnt soyben (Glycine mx) on seed yield nd gross profit mrgin, Weed Technology, vol. 15, pp , [16] R. J. Krtochvil, J. T. Perce, nd M. R. Hrrison Jr., Row spcing nd seeding rte effects on glyphoste-resistnt soyben for mid-atlntic production systems, Agronomy Journl, vol. 96, no. 4, pp , [17] E. Coetzer, K. Al-Khtib, nd D. E. Peterson, Glufosinte efficcy on Amrnthus species in glufosinte-resistnt soyben (Glycine mx), WeedTechnology, vol. 16, pp , [18] A. S. Culpepper, A. C. York, nd L. E. Steckel, Glyphosteresistnt Plmer mrnth mngement in cotton, in Proceedings of the Southern Weed Science Society, vol. 64, p. 226, [19] J. D. Reed, P. A. Dotry, nd J. W. Keeling, Plmer mrnth (Amrnthus plmeri S. Wts.) mngement in Glytol + LibertyLink cotton, in Proceedings of the Southern Weed Science Society, vol. 64, p. 260, [20] J. R. Whitker, A. C. York, D. L. Jordn, nd A. S. Culpepper, Plmer mrnth (Amrnthus plmeri) control in soyben with glyphoste nd conventionl herbicide systems, Weed Technology, vol. 24, no. 4, pp , [21] Ignite 280 herbicide lbel. Byer CropScience, Reserch Tringle Prk, NC, USA, 2012.

8 Veterinry Medicine Interntionl Scientific The Scientific World Journl Journl of Food Science Botny Ecology Agronomy Submit your mnuscripts t Applied & Environmentl Soil Science Biodiversity Journl of Forestry Reserch Nutrition nd Metbolism Evolutionry Biology Plnt Genomics Advnces in Agriculture Genomics Biotechnology Reserch Interntionl Cell Biology Psyche Microbiology