,12‘l.1,1.&‘11 ”2.3. .13: L2 full? ’ ‘22" k. “TC“! .. :2‘21. - 31W» " 555231.123M322ULL, .'2:‘:‘3“91§"f¢““}3‘4 “ML” LgLLfiu ' 2213’ . 11:22. 22.323 2 ‘1” W “1&2le “(‘1‘ 32:2. {352 fl “Uh i." 25.2“ 22 23‘ ‘ M ‘12“ £22 2:". ’1""zi‘21‘;.‘2*2*7‘l‘§"l§§} W3. “#04 Lida?“ L , .72: ‘. ‘1"‘3 .3 41:" [X X1 “31.; _ 23:35 "’ ' .323; 2.. {2321, (NJ: km) “42‘ 31‘ P E3§§mkl '1‘} 3‘32“" 2‘3. “ Wfis.‘ . 5%‘2 “ “23 .I'! ““5; .5: 643“ 31".” (1 , Q :‘HM‘ £33311”? '11? m ‘2.“- . ‘- "' ' - ‘ ‘ 2;: ’ 352w? ””2... ".3 433"", :22L .4. 523* 3}; 2:3; ' k ‘ ‘2. ca: .11.“ : :‘fi'pwtfi‘mz‘wn _ xfsr‘khg%u £th {L52 P7» $213 r’éffié $13313“ ‘3” " ‘ :5» 2,. "n :2. {32! - . s79~ 37.5.4 fl 2 2. s i k I f1!" 5&4“! ‘ ’71" 2‘5“?" 3". :‘2 ‘ 2; 73:32?” wgifiakflg _ .M . 3.22.2.1 la. f. 'hSE 33/ 52332? 21.31 53%; 1 2‘2. ? ‘5‘; ' 32922321: ”N; N 1' fig}; 3 '1? 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Meggitt MSU is im Affirmative ANION/Equal Opportunity Illrrritult'on 0-12771 MSU RETURNING MATERIALS: PIace in book drop to L1BRAR155 remove this checkout from - your record. FINES wii] be charged if book is returned after the date ‘ stamped below. "or. POSTEMERGENCE NEED CONTROL SYSTEMS IN SOYBEANS (GLYCINE MAX (L.) MERR.) By Jerry Leo Niihm III A DISSERTATION Submitted to Michigan State University in partiai fuifiilment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Crop and Soil Sciences 1984 :5 / 8 “MI 672's? ABSTRACT POSTEMERGENCE NEED CONTROL SYSTEMS IN SOYBEANS (Glycine Max (L.) Merr.) By Jerry L. Nilhm Postemergence weed control systems for annual weeds and quackgrass (Agropyron repens (L.) Beauv.) were evaluated over two growing seasons. Postemergence applications of tank-mixed grass and broadleaf herbicides controlled annual grasses, but were not as successful in the season- long control of certain broadleaved weeds as were standard preemergence applications of soil applied herbicides. Excellent quackgrass control was obtained at several locations with fall and spring applications of nonselective herbicides glyphosate flyiphosphonomethyl)glycine) and SC-0224 (trimethylsulfonium carboxymethyl-aminomethyl phosphonate) applied in several rates and spray volumes in several tillage systems except for spring applications following fall moldboard plowing. At another location, spring applications of these herbicides resulted in poor control of quackgrass growing in 38-cm tall wheat (Triticum aestivum L") stubble due to poor coverage. Generally, longer control was obtained with non-selective than selective postemergence herbicides. Nith postemergence herbicides, early applications to quackgrass at the three-leaf stage were not as effective as later or split applications in spring moldboard plowed soybeans. There were fewer differences due to time of application in spring moldboard plowed soybeans in narrow rows; fall chisel- or fall moldboard plowed soybeans; or in several systems of no- till soybeans. Generally, equally high soybean yields were obtained with non-selective and selective postemergence herbicides as long as quackgrass was controlled before exceeding the five-leaf stage. Poor control of late-season quackgrass regrowth did not influence yield. Acifluorfen (5-(2-chloro-4-trifluoromethyl)phenoxy)-2-nitrobenzoic acid) and bentazon (3-isopropyl-lfi-2,l,3-benzothiadiazin-4(3fl)-one-2,2— dioxide) in tank-mix with postemergence grass herbicides resulted in significantly increased late-season regrowth of quackgrass suggesting reduced translocation of grass herbicides. Acifluorfen and bentazon reduced translocation of 14C-haloxyfop-methyl (methyl 2-(4-((3-chloro-5 (trifluormnnethyl)-2-pyridinyl)oxy)phenoxy)propanoate) out of the treated area into the lower leaves. Acifluorfen reduced translocation of 14(3«-DPX-Y6202 (2-(4-(6-chloro-2-quinoxalinyl)oxy)phenoxy)propionic acid, ethyl ester) out of the treated area into the leaf tip and bentazon reduced absorption of 14C-DPX-Y6202 into the quackgrass plant. ACKNOWLEDGEMENTS I certainly enjoyed my time here and it is a great honor to receive this degree fronilWichigan State University. I wish to extend my appreciation to the people who were involved in this research project. Sincere thanks is expressed to my major advisor Dr. William F. Meggitt, for his invaluable guidance, wisdom, and friendship these past three years which have enabled me to become a better weed scientist and person. I wish to thank Dr. Donald Penner for his fellowship and assistance hithe laboratory aspectscflithis project. The input of Drs. Alan Putnam, Hans Kende, and Bernard Knezek is also greatly appreciated. I wish to thank Cindy Prentice, Frank Roggenbuck, Kay Keating, and especially Gordon Robinson for their technical assistance. Sincere appreciation is extended to John Pawlak, Veldon Sorensen, Jim Kells, and especially to|m Pogpcou uwmzn .pmmp mace; mpavp_:s m.:moc3o ow mcwugouom Fm>m_ zpvanmnogn xm any on pcmgmmmwv xppcmowwwcmwm pee wee copuwF coEEou a An emZOFFow cowpmzpm>m cm cwzuvz mcwwzm w mm m cor mum mm m cm N¢.o + #N.N :PNznwLawE + Lopzomp< peprmmcp mucmmcmewmea ugmucmwm e-e we a we e-e we a oo_ ew.o + mN.o eONeeeee + _»eees-eoexxere: a-e am a o e-e mm e oo_ ew.o + e_.o eeNeeeee + _seeee-aoesxepez m-e mm e-o mm m-e mm a co, em.o + mN.o eeteo:_ewoe + _»eeee-aoesxopez e-e mm a Fm m-e mm L cor em.o + e_.o eaeeo:_e.ue + _sepee-aetsxopa: m-a mm e-e mm a-e mm e co, em.o + wN.o eaeeo=_ewue + _»e=e-aoeeNa:_a e-e mm v-8 as a-e mm e-a ma em.o + mm.o eaeeoszeaee + ewesxoeeem ---- ................... N-------- ........... hee\mxv vcrou uzaem vzsou cemxm mpma owcprmmLp mucwmgmsmpmoa a POLPCOU U003 .emmm_ ”Hz .mewwees amen .wucmmLmEmpmoa argue vmquam mmuwuwnew; sew: mcwwnxom cw memo; Fwsccm $0 Foepcoo .F mrnme 48 .memucmzcmnEm_ :oEEou n cPou use .umwzmwa pooeums n saga .cmmzmme coEEoo u stow .mmmemuemxccmn n cmxmv .e;\4 m.m pm mmepcmucou Fwo aoeu cmu:_ucw :ONmpcmn mcwcempcou mpcmEpmmepu .mm\mp\~ co umpmzpm>m Foeucou vmmzn .pmmp mace; wravurzs m.:ou::o op mcwveouum Fm>mp aperwnmnoea xm ecu pm pcmcmmewu xpucmowewcmwm po: mew empumF coseoo m an uszFPow Cowpe:_e>m cm :_;uw3 mammzm a Foewcoo two: A am a oo_ a.e am .e no Ne.o + eN.N eeNseeeeee + LeFeoe_< pcmeumoeu mocmmemewmem uemucmpm a o a o e-a om a oo_ em.o + mm.o eenepeae + Pseeee-aoesxo_e: a o e o e-a o_ a cor em.o + e_.o eonepeme + _sepee-eoesxo_ez .-e mm a see m-e mm t-e mm em.o + m~.o emcee=_ewee + Pseeme-aee»xoeez .-e em a co? o oo_ e-u em em.o + e_.o eateo=_eeoe + Pseeee-aeesxepe: m-e em a o e-e om e co? em.o + w~.o eONeeeae + Nome>-xae a-e mm a oo_ o oo_ e we em.o + mm.o eaeeoeeeaee + Nome>-xao v-8 cm a 00F m-e mm a me em.o + mm.o eeeeo=_e.ee + _»B=e-aeewne=_a _-e Fe o oo_ m-e mm e-u me em.o + mN.o emeeoseewoa + ewesxoeemm ---- ........... - ..... e--------- ...... ------- Aee\m¥V ucroo uzmgm. cacao neoxm mpmm oucmEpmmLp mucwmumsmpmoa .mocmmgmsmumoa mpm— umPPQQm mmuwuvnem; sew: mammn>0m cw mummz szccw we Foepcou .emma_ we: .meemees “mam .N ePeae 49 late postemergence treatment for the control of these weeds. Barnyardgrass control from postemergence treatments containing sethoxydim and fluazifop-butyl was significantly lower when applied to grass in the five to seven leaf stage than to grass in the two to four leaf stage (Table 1). Barnyardgrass control from haloxyfop-methyl plus acifluorfen at 0.14-plus 0.56 kg/ha was significantly lower when applied late postemergence compared to early postemergence (86 v. 100%L Increasing the rate of haloxyfop-methyl to 0.28 kg/ha significantly increased barnyardgrass control and there was no significant difference in control between the two times of application with this rate. However, this was not observed from late postemergence applications of the lower rate of haloxyfop-methyl tankmixed with bentazon as this treatment resulted in 100% control (Table 2). Similarly, late postemergence applications of DPX-Y6202 plus acifluorfen resulted in significantly lower barnyardgrass control than DPX-Y6202 plus bentazon (88 v. 100%, Table 2). This shows that acifluorfen can cause an antagonistic response in annual grass control when applied in a tankmix with postemergence grass herbicides. As with early postemergence applications, later postemergence applications of treatments were still ineffective in controlling common lambsquarters. Major emergence of this weed occurred after the late postemergence applications, thus, postemergence applications were ineffective since only sprayed weeds were controlled. Rapid growth of common lambsquarters occurred prior to full crop canopy development and was undoubtedly aided by lack of interference from other weeds that .. «vi.- .uLL 13...... 5102.....1unnu..mnwm..n..lv MT... . 7 . 1 i U 111.. ll.ll.. ..llli. .e 1..l.n.ll....li..n\t.l 11.1171. .;.\.1 ii . i lPI...H._-i. 50 were controlled from the herbicide applications. Common lambsquarters growth was so prolific that by the end of the season the plots could not be mechanically harvested. Even though common lambsquarters interference occurred after the critical soybean growth stages which most directly affect yield, ease of harvest is of major importance to a grower. Since by midseason it was evident that none of the postemergence treatments applied would be viable methods for soybean production, no further evaluations were made. In 1982, postemergence weed control systems did not compare favorably with the standard preemergence treatment of alachlor plus metribuzin. The 1983 postemergence weed control systems were deisgned to deal with some of the problems encountered in 1982. These included mechanical cultivations, no late postemergence applications to weeds (particularly grasses) potentially too large to control, and utilization of soil applied broadleaf herbicides followed by postemergence grass herbicides. In addition, in 1983 the grass herbicide rates were reduced to 0.T4 kg/ha based on the success in 1982 of early postemergence applications with 0.28 kg/ha. This would subsequently reduce costs to growers should all of these herbicides receive registration for use in soybeans. In 1983, yellow foxtail was the predominant grass species present. Common ragweed and redroot pigweed were also present as in 1982. However, there was no common lambsquarters present as in 1982. Good to excellent season-long control of yellow foxtail was obtained from postemergence applications of treatments containing 51 sethoxydinn DPX-Y6202 and haloxyfop-methyl (Table 3). Of these, only applications of haloxyfop-methyl resulted in reduced foxtail control when tankmixed with acifluorfen compared to bentazon, and this occurred a the late-season rating only. However, this reduction in control was not severe. Applications of fluazifop-butyl with both acifluorfen and bentazon resulted in very poor and significantly reduced yellow foxtail control at the midseason rating compared to the other postemergence grass herbicides. Although growth was slowed, the grass had not become necrotic as with the other grass herbicides. By late season, the yellow foxtail treated with fluazifop-butyl plus acifluorfen was eventually controlled, but those treated with fluazifop-butyl plus bentazon were not. Ii:is.not clear why this occurred in 1983 but not in 1982, although, the species were different in the two years. As in 1982, acifluorfen provided greater control of the broadleaf weeds present than acifluorfen. However, the standard preemergence treatment of alachlor plus metribuzin resulted in significantly greater broadleaf weed control than any postemergence treatment at the midseason rating and was still showing complete control of all weeds at the late season rating. Because of the season-long weed control, the standard preemergence treatment had significantly higher soybean yields than any other treatment including the hand-hoed weed-free treatment. lkispite of caution, hand-hoeing occasionally injured or removed some soybean plants plus caused considerable soil disturbance throughout the season, .oooZmoL coesoo n 3Lou .ooozmwo uooeoog n 3oem .Fwopxoe 3oFFo> n peo>o .coeeozrewoo new; 23 NE one .5528 fit: 93% Loop poooxo 9:.— m.N um ouogucoocoo 75 no.8 853:8 3:958: oocomgosoumoao mw\om\m i :omoom opo_ oco mw\mp\m . comoomows Loco mcovuoapo>o Foepcoo now: we mouooo .pmou omcoe o_ova_:s m.coo::o ou mcwocoooo _o>o_ xpWFPnoooeo &m we“ on pcoeowewo ucoowmwcmem poc mew coupoP cosEoo o an oozoppom cowpo:_o>o co swear; mcoozo 52 aim mom? “cospooep oz w-o _eom eoec ewe; ooee-oeex w oomm _ oo_ o oo_ o oo_ E oo_ c oo_ ? oop No.0 + «N.N :wNzowepoe + Lopsoop< pcosuooep monomeoEooeo oeoocopm oto oom_ ole m_ o m_ o oo_ aim or oio mm wt; mm om.o + o_.o coNopcoo + PaguoeiooezonMI vim mmmm mi; mm cum mm one mm film m“ min me :1» mm om.o + or.o coeeos—wwoo + FxgpostooexonMI eio meow oio mm oio mm o ooF one om one w— w oo_ ow.o + <_.o :oNopcon + ~o~m>ixao gum omom xi; om 0.: mm oio mo xi; mm wio mm wt; mm mm.o + o_.o coeeozpwwoo + Nomm>ixoo o-p mwe_ o-e om e-a em a Re 2-“ e_ E-o mm a om em.o + 4F.o eo~moeoe + _ze=e-aoe.~eepa 51o o—om gt; mm 0.: mm o-o mm Ft? mm Tim on aim mm mm.o + o_.o someoopewoo + PapooioowwNoz—J o-o mmwp oio om oio om win om m m oio om win Pm ow.o + «F.o :oNobcon + Ewozxogpom vim Noam xiv om otw mm o-o mm xi; mm but mo :14 mm om.o + op.o coeeoopwwoo + swozxozpom bee\oso ......... e ..................... a .......... nee\oxv opoF> 3eou .3aem ~+o> zeoo goem peo> opom psoEuooep oocomgoEopmoa :mwnxom v t b U 3 . .U u . comoom oped , comoomoez apoepcoo oooz. .emwm_ we: .oeameas anew .oocomsosopmoo >Fsoo oovpooo moowowoeo; sow: mcoooxom c? memo: Fozcco mo Poepcou .m ofiooh 53 whereas, the standard preemergence treatment was completely undisturbed. Reflective of weed-control ratings, treatments of grass herbicides containing acifluorfen yielded significantly more than those containing bentazon, except with DPX-Y6202. Although not significantly different statistically, the yield from a treatment of DPX-Y6202 plus bentazon was numerically less than that of DPX-Y6202 plus acifluorfen. Table 4 shows the effects on weed control and yields of a cultivation approximately 4 weeks after postemergence applications of herbicides. Midseason ratings were taken immediately prior to the cultivation. Cultivations are particularly beneficial hiincreasing broadleaf control in plots treated with bentazon. Due to this increased broadleaf control, there was no significant difference in yield whether with acifluorfen or bentazon when a cultivation was performed. However, cultivations did not increase yields of treatments containing acifluorfen (Tables 3 and 4). Cultivation also provided significantly greater control of yellow foxtail with fluazifop-butyl plus bentazon (Tables 3 and 4). Treatments of herbicide plus cultivation had significantly higher soybean yields than either no treatment or early cultivation plus late cultivation. There were no significant differenceS'hiydeld between any of the postemergence herbicide plus cultivation treatments whereas without cultivations, the treatments containing acifluorfen yielded significantly more than those containing bentazon (Table 3). However, the standard preemergence treatment yielded significantly more than 54 most of the postemergence herbicide plus cultivation treatments (Table 4). Although cultivations can increase broadleaf weed control with herbicide treated plots, a cultivation cannot substitute for broadleaf weed control with herbicides. Early postemergence applications of grass herbicides only followed 3 days later with a cultivation resulted in severe broadleaf pressure, particularly from common ragweed later in the season (Table 5%. Yellow foxtail control remained excellent for the duration of the season despite a cultivation 3 days after application. However, yields from all herbicide treatments except haloxyfop-methyl, were not significantly higher than the control and there were no significant differences between yields from the herbicide treatments themselves. This is not a presentable option for broadspectrum weed control. Since broadleaf weeds are seemingly more difficult to control season-long with postemergence herbicides, it may be practical to make a preemergence application oflnetribuzjrifor broadleaf weed control followed by a late postemergence application of grass herbicides (Table 6). Since metribuzin has some preemergence grass acitivity, the grass herbicide rate was reduced to (L07 kg/ha. The early-season weed control evaluation showed very good broadspectrum weed control from metriuzin only. The significant contribution of alachlor to broadspectrum weed control with alachlor plus metribuzin was also seen. Addition of postemergence grass herbicides was able to maintain high levels of yellow foxtail control. However, such applications may be 55 .oooZmoL cossoo n stow .ooo3mwo pooeooe n saga .Fwouxow 3oP—ox u pmo>o .cowgoapwwoo saw: o;\4 N._ oco :oNoucon cow; omoep toe poooxom::1_m.m no opoepcoocoo Fwo ooeo oocwoucoo mucoEpoocu oocooLoEoumooo coxop mcwuoe comoomowz _o>oF soweeeaeoea am tee .:o_po>wo_=o on Loweo .mm\om\m . comoom opoF oco mm\w—\n . comoomows Logo cowpozFo>o Poepcoo oooz wo mopoon .pmou mace; opowppze m.:ooc:o op mcwoeoooo om pcoeoewwo prcoowewcmwm yo: oeo Loppo— coeeoo o xo ooZoFPo+ cowpozpo>o segue: mcooZo e-e mmN_ oeeEpeoeo oz w-o Feom meet owe: eoee-eee: o-e omoP cowoe>epreo ooe_ meeaoe>epreo »_eem h eemm F oo_ e co? m ooF 5 oo_ e oo_ a cor Ne.o + 4N.N ewNznaepee + eoeeoep< “cospooep monomeoeooeo oeoocoum o-o mmNN o-o eo e-e o“ o-o mm a o_ o-m mm e-e mm em.o + e_.o eeNeoeoe + _»eooe-aoexxorez P-o omom _-x mm 0-2 om o-e om _-h mm h.@ we e-e we om.o + e_.o eoeeo=_eaoe + _»eoes-aoexxofie: a-o memm o-o oo _-o mo o oo_ o-e ON a o_ w.@ mm ew.o + e_.o eONeeeae + Nomo>-xao a-o Keem F-” om 0-x em o-o om 3-: mm e-o mm w-e mm om.o + e_.o eoeeo=_e.oe + Nomo>-xao w-e comm o-e OR o-” ma non mm e-e m_ e-a or e om em.o + e_.o eeNaeeoe + _»o:e-aoe.Ne=_a “-5 ooem _-x mm 0-5 om o-e om x-o om h.@ we o-e om om.o + e_.o eoeeo=F4_oe + fisoze-a0ta~e=_a e-o _oom e-o we e-e mm o-e em o-e mm o-e mm o-a oe em.o + e_.o eONeoeae + Ewesxoepem h-e owew F-x Km 0.” mm o-o Am F-. om L-m oo w-o em om.o + 4P.o eoeeeefieeoe + eeosxeeoom AeexoxV .--------4----------- ......... N----------- Aae\oso opow> 3Lou saga pwo> zeoo goem peo> opom “cospoocu oocomeoeopmoa eeoesom e - o o . o o e o comoom moo; comoomwwz oFochoo oooz . . - .amwoP we: .oewmees omen .eoeee>epeso mum? o An oozoFFom oocomcoEopmoo >Fsoo oowrooo moowovoeo; sow: mcoooxom cw moooz Poscco eo Focucou .o orooh 56 .ooo3mee :oesoo n zeoo .ooozmwo pooeooe n zeta .Feepxow gor—ox n peo>o .coeco:_ewoe sew; e;\4 N.F o:e.co~epcoo sue; omen» toe poooxoie;\4 m.N we opeggcoocoo Pwo ooeo oocwepcoo mucospeoeu oocoaLoEmumooo .mw\ON\m I commwm wwwp Ucw mm\wp\u I comwmewE nwLm mcowvmzrm>w FOLwcou nmwz mo mmuwon .pmop mace; oromp~zs m_:eo::o ou mcwoeoooe Po>o— mew—woeooeo em ecu we ucoeowevo AFHceoemvcmwm poc wee LoupoF :oEEoo e he oozoF—ow :owpezpe>o :e segue; mceoze one mom? . pcoEoeoLu oz e-o _eeN mete ewe: eeoe-eeez e-e oee_ eoeee>_e_=o eee_ meeeee>eo_=o »_eee e eeem _ oer o co? o oo_ 5 oo_ e oo_ e cop Ne.o + 4N.N eLNeeeeeoe + eo_eoe_< peoEueoep mocomeoeooeo oeeecepm e-o emm_ e-e OF e-m ow e oo_ e-e ee e-e ee e-e eo er.o _seoee-aee»xope: o-e eoep e-e o_ e-e em e-o em e-o me x-e me e-» mm e_.o Nome>-xae o-e eme_ e-e OF x-o ee e-e em e-e ON e-e me e-e ea e_.o _se=e-aoewee=_a 8-2 moo, e-e er e-e oe e oer e-e we e-e me e-e em e_.o Eweexoeeem Aee\oxe .......... e--- ........ ----------e----------- Aee\exv e_ew> zeoo seem eee> . seeo_. zoom . pee> .eeee peeEeeeee eoeeoeeEeemoa :mwnkom U u bu b b v u cowwwm mum; . cemmwmvwz opoepcooeooz .emmmP we: .mcwmceo pmem .cowpe>wppoo AFLeo ce xo eoZOFFow moowowneo; mmeem go mcowpeowrooe oocomeoeoumoo sew: mceoozom cw memo: Pezcce eo Fogpcou .m oroeh 57 .mw\om\m t comemm over oce mm\mfi\m . comeomows .mw\m\n . comeom zFLeo .zpo>wpooomoe .ez\mx Ne.o + em.~ pe :wNaoweuoe oce Lopzoep< ”ucoEpeoLu oocomeosooeo ogeocepmo .ooozmee coEEoo n zeou .ooozmwo pooeooe n Zoez .F_epxow zoP—oz n peo>o .ez\z m.m we opeepcoocoo Fwo ooeo mayo ez\mx no.o we moowowaeoz mmeem wo mcowpeowpooe oocomeosoumoo mez\mx Ne.o . cw~znvepoe mo mcovpeowyooe monomeosoocao .pmop emcee o—owp note mcowpeepe>o Foepcoo oooz eo moves a Pas m.:eo::o op mcwoeoooe Fo>o— zpwpwneooeo zm ozu we ucoeowmwe zypceovewcmwm po: oce LopeoP :oEEoo e zo oozoppoe :owpe=~e>o ce :wzpwz mceoze pie mam? pcosueoeo oz e-e _eem mete ewe; eeoe-eee: w eemm F oo_ o oo_ o co? E 00? : oor w COP : ooF ; oop w oo— cw~zowgpoe + Lo_:oer< opcoEpeoLp mocomeoEooLm oeeecepm vim Poem xi; mm o oo_ ole Fm Fifi Pm E-_ Fm zto Pm 5.? mm elm we hie om Pzzposioowzonez + cw~=owepoz vim nmmm. x.: mm o.: mm oio om ziz mm 51m mm zio Fm rim mm mum mm zio Nu momm>ixao + cw~sowcpoz z-o comm x-e we e-e em e-e om x-e me 5-x om moo me e-_ em e-m he e-e om reuse-aeew~eeze + eeeeeweeez him meow xi“ em our om o-o mm Fix mm sip mm gum mm :in mm cum mm wio mm Evozxozpom + ew~zowepoz Aez\mxv . ..... title--- ..... i- i- ...... -intiui ..... --iiiitiiwiiiitiiiiu erow> ezeoo egoez ewwow. ozsoo egoez epwww ozeou ozmez op$o> opcospeoep ceoozom comeom opez comeomewz. comeom afieem LFoepcoo too: .ememz we: .oeemees emee zo eozorpow cw~znwepos mo :owpeow—ooe mocomcoEooeo e saw; mceonxom c? memo: Feocce mo —ocpcoo .moowowosoz mmeem eo mcowpeowfiooe oocomLoEopmoo .m orneh 58 unnecessary and give low cost/benefit returns due to the relatively high levels of grass control from metribuzin itself and the low grass densities at the time of application of postemergence grass herbicides. It would be considerably easier and more economical to make a single broadspectrum preemergence application rather than one application each for broadleaf and grass control. SUMMARY Postemergence tankmix applications of grass and broadleaf herbicides effectively controlled treated weeds if the proper broadleaf herbicide was matched to the weed problem. In these experiments, acifluorfen was more effective than bentazon in controlling the broadleaf weeds present. Poor weed control and low yields from treatments containing bentazon were increased with cultivations. However, lack of soil residual activity for late emerging weeds and for those not adequately covered with spray compounded with potential for reduced grass control (antagonism) with tankmixes were some of the shortcomings of a total postemergence weed control system in soybeans. The standard preemergence treatment of alachlor plus metribuzin was consistantly higher in both weed control and soybean yields than postemergence applications and were easier to apply requiring fewer trips across a field. 10. 11. 12. LITERATURE CITED Buhler, D. D. and 0. C. Burnside. 1983. Soil activity of fluazifop, sethoxydim and Dowco 453. Abstr. Weed Sci. Soc. Am. p.29. Coble, H. D., F. M. Williams and R. L. Ritter. 1981. Common rag- weed (Ambrosia\artemisiifolia) interference in soybeans (Glycine Dawson, J. H. 1964. Competition between irrigated field beans and annual weeds. Weeds. 12:206-208. Dexter, A. G., J. D. Nalewaja and S. D. Miller. 1984. Antagonism between broadleaf and grass control herbicides. Abstr. Weed Sci. Soc. Am. p.5-6. Handly, J. V., B. C. Gerwick and R. D. Vatre. 1983. Preemergence potential for haloxyfop-methyl in soybean production. Proc. North Central Weed Control Conf. 38:10. Kells, J. J. 1982. Grass control in soybeans (G1 cine max Merr.) with selective postemergence herbicides. P5. 0. Dissertation. Michigan State University. 122 pp. Kinsella, J. and B. Burdick. 1983. Utilizing post-emergent chemicals for total weed control in soybeans. Proc. North Central Weed Control Conf. 38:16-17. Renner, K. A. and R. G. Harvey. 1983. Postemergence control of giant foxtail (Setaria faberii Herm.) and wild proso millet (Panicumjmjjiaceugyly) in soyBeans. Abstr. Weed Sci. Soc. Am. p.7-8. Rick, S. K. and F. W. Slife. 1982. Postemergence and residual grass control in soybeans. Proc. North Central Weed Control Conf. 37:66. Schmidt, 0. K. 1983. Tankmix and sequential applications of acifluorfen-sodium. bentazon, fluazifop-butyl and sethoxdim for postemergence weed control in soybeans. Proc. North Central Weed Control Conf. 38:154. Staniforth, D. W. and C. R. Weber. 1966. Effects of annual weeds on growth and yield of soybeans. Agron. J. 48:467-471. Williams. C. S. and L. M. Wax. 1983. The interaction of bentazon and haloxyfop or sethoxydim. Proc. North Central Weed Control Conf. 38:41. 59 CHAPTER 3 QUACKGRASS (Agropyron repens (L.) Beauv.) CONTROL IN SOYBEANS (Glycine max (L.) Merr.) ABSTRACT Experiments to evaluate quackgrass (Agropyron repens (L.) Beauv.) control in soybeans (Glycine max (L.) Merr.) were established at several locations under different tillage and crop rotation systems. Nonselective herbicides glyphosate (N-(phosphonomethyl)glycine) and SC- 0224 (trimethylsulfonium carboxymethylaminomethyl phosphonate) provided poor control of quackgrass growing in tall wheat (Triticum aestivum L.) stubble due to poor coverage. Excellent control was obtained with both herbicides at other locations with spring and fall applications except with spring applications following fall moldboard plowing. Greater quackgrass control one year after spring application of glyphosate was obtained in a no-till soybean field which had been tilled and planted to soybeans the season prior to treatment than in one in which no crop had been planted the previous season and had developed a quackgrass sod. Significantly lower quackgrass control was obtained with 0.84, 1.68 and 2.52 L/ha of glyphosate applied in a spray volume of 37 L/ha 6O 61 than in 65, 131 or 262 L/ha. Postemergence applications of the grass herbicide haloxyfop-methyl (methyl 2%(4-((3-chloro-5-(trifluoromethyl)- 2-pyridinyl)oxy)propanoate), DPX-Y6202 (2-(4-((6-chloro-2-quinoxa- liny1)-oxy)propionic acid), and fluazifop-butyl ((ibutyl-Z-(4-((5- trifluoromethyl)-2-pyridinyl)oxy)phonoxy)propanoate) were generally' more effective than sethoxydim (2-(1-(ethoxyimino)buty1)-5-(2-(ethyl- thio)propy1)3-hydroxy-2-cyclohexen-l-one). Early postemergence applications following spring moldboard plowing to 101x>15 cm tall quackgrass with two to three leaves were not as effective as later or split applications because spring plowing prohibited uniform shoot emergence. However, all applications were equally effective in a spring moldboard plowed, narrow-row soybeans situation as well as wide- row soybeans which had been fall moldboard plowed, fall chisel plowed or in no-till. Fall applications of postemergence grass herbicides did not provide season-long quackgrass control the following season. Cultivations were as effective as a second application of herbicide. Despite varying levels of quackgrass control from different herbicide treatments, nearly all treatments resulted in significantly increased yields over no-treatment when applied prior to the five-leaf stage of quackgrass. Higher subsequent season control was obtained with nonselective than selective-postemergence herbicides. INTRODUCTION Quackgrass is considered to be one of the world's worst weeds (7, 11). In corn, there are several effective soil applied herbicides available for quackgrass control, but none are available in soybeans. Glyphosate (N(phosphonomethyl)glycine) is a non-selective herbicide which effectively'controls quackgrass with fourcn'more leaves when applied in the spring before tillagecn‘in the fall after harvest (1, 4, 8). Tillage and time of application have been shown to influence quakgrass control with glyphosate. For example, spring applications following fall plowing are ineffective because all shoots had not emerged at the time of application (3, 14, 15). Fall applications have been shown to be more effective than spring applications (2, 9, 142). Selective postemergence applied grass herbicides are new herbicides which have demonstrated effective quackgrass control. Applications of sethoxydim (2-(1-(ethoxyimino)butyl)-5-(2-(ethylithio) propyl)3-hydroxy-2-cyc1ohexen-l-one), fluazifop-butyl ((1)-butyl-2 (4- ((5-trif1uoromethyl)-2-pyridinyl)oxy)phenoxydpropanoateL,haloxyfop- metnvl(methyl 2-(4-((3-chloro 5-(trif1uoromethyl)-2-pyridinyl)oxy) propanoate) and DPX-Y6202 (2-(4-((6-chloro-2-quinoxaliny1)oxy)propionic pyridinyl)oxy)phonoxy)propanoate) have been shown to be more effective in controlling quackgrass in the three- to five-leaf stage than at 62 63 later stages (5, 6, 10, l3, 16). However, just as quackgrass control with glyphosate is influenced by various cultural factors, so may be the postemergence grass herbicides. Therefore, the objectives of this research were to l) evaluate quackgrass control with postemergence applied grass herbicides under several tillage and cultural systems and compare control to that obtained from applications of the nonselective herbicides glyphosate and SC-0224 (trimethylsulfonium carboxymethyl aminomethyl phosphonate) and, 2) determine the effects of these control measures on soybean yield. MATERIALS AND METHODS Field experiments were conducted in 1982 and 1983 at five locations in areas of dense quackgrass infestation. All herbicide applications were made with a compressed air tractor sprayer using flat fan nozzles. Visual ratings of quackgrass control were made at several times following herbicide application. Ratings were based on a 0 to 10 scale where 0 indicated no quackgrass control and 10 indicated complete control. Untreated control plots were used as a basis for no control. Rating data were converted to decimal form, subjected to the arcsin data transformation and then analyzed for mean separation using Duncan's multiple range test. Presented means are non-transformed and expressed as percent. Rates of glyphosate and SC-0224 are expressed on an acid equivalent basis. Postemergence grass herbicides were applied as early postemergence, late postemergence and split applications. A 64 split applicaion means that half of the total rate was applied early postemergence and half applied late postemergence. Two weeks separated early and late postemergence applications. No treatment resulted in soybean injury. The first experiment was established in Clinton County in 1982 near Dewitt, Michigan on a Capac loam. The field had been planted to wheat in 1980 and harvested in 1981, and had not been tilled following harvest. 'The entire area contained 35 to 40 cm tall wheat stubble. All herbicide applications were made in a spray volume of 215 L/ha at a pressure of 208 kPa. Preplant applications of nonselective herbicides were made on May 16, 1982 when the quackgrass was 20 to 30 cm tall with four to six leaves. Half of the experimental area was moldboard plowed and disked on May 20, 1982, and the other half was left no-till. The experimental design was a randomized complete block with a split with four replications, the main factor being tillage. The field‘was not able to be planted at the same time. The conventional-till half was planted on May 25 and the no-till half was planted on June 2, following a burn-down application of paraquat at 1.12 kg/ha on May 25. The soybean variety planted was “Hodgson 78" with a 76 cm row spacing. A preemergence application of alachlor (2-chloro-2',6'-diethyl-N- (methoxymethyl)acetanilide) and metribuzin (4-amino-6-t_er_t_-butyl-3- (methylthio)-a§-triazin-5(H)-one) at 2.24 and 0542 kg/ha was made following planting to control annual weeds. Plot size was four rows by 12.2 m. Due to the different planting dates, postemergence applications of herbicides were made on different dates. 65 Early postemergence applications were made on June 10 in conventional- till and on June 26 in no-till. Quackgrass at this time was 10 to 15 cm tall with three leaves and soybeans were in the first trifoliolate stage (V2) in both experiments. Late postemergence applications were InadecuiJune 26 Hiconventional-till to 20 to 25 cm tall quackgrass with four to five leaves and to soybeans in the second to third trifoliolate leaf stage (V3 to V4). In no-till, late postemergence applications were made on July 9 to 20 to 30-cm quackgrass and to soybeans in the third trifoliolate leaf stage (V4). Visual control ratings were taken June 25, July 18,.August 1, September 24 and the next spring on May 5, 1983. Due to the heavy thatch layer of wheat stubble and desiccated quackgrass in no-till, poor seed placement occurred during planting and non-uniform soybean stand was established. Therefore, yields were taken only in the conventional-till portion of the experiment. Yields were taken on October 14 by randomly harvesting 3 m of each of the two center rows of each plot and a mechanical thresher was used to separate the soybean seeds. A second quackgrass control experiment was established in 1982 on the Michigan State University Agricultural Experiment Station in East Lansing on a Capac loanL The field was moldboard plowed, disked and field cultivated on June 7 and planted to 'Evans' soybeans with 24 cm row spacing on June 8. Early postemergence applications of herbicides were made on June 25 when the quackgrass was 10 to 18 cm tall with three to four leaves and the soybeans were in the unifoliolate leaf stage (V1). Late postemergence applications were made on July 9 when 66 the quackgrass was 20 to 35 cm tall and had three to five leaves. All herbicide applications were made at a spray volume of 262 L/ha at 324 kPa. The experimental design was a randomized complete block with four replications. Plot size was six rows by 10.7 m. Visual ratings were taken on July 23 and October 11. ‘The four middle rows of each plot were harvested for yield on November 14 using a small plot combine. In 1983, another experiment was established on the Michigan State University Agricultural Experiment Station in East Lansing on a Colwood-Brookston loam This field had not been cropped since 1981 and a dense quackgrass sod had developed in 1982. Fall applications of herbicides were made on October 4, 1982 when the quackgrass was 10 to 20 cm tall with three to four leaves. Fall treatments were applied in a spray volume of 215 L/ha at 208 kPa. One month prior to this application, the tall, mature quackgrass was knocked down with a tandem disk. This operation was necessary because the existing quackgrass was too tall for spraying. However, the disk was set so that the underlying soil was not disturbed and only the quackgrass stems were knocked down. Control evaluations were made the next spring on May 15. Half of the field was moldboard plowed on November 15 and the other half remained no-till. Experimental design was a randomized complete block with a split, the main factor being tillage. There were three replications. Spring preplant applications of non-selective herbicides were made on May 16, 1983 when the quackgrass was 20 cm tall with three to four leaves. Four spray volumes were compared. These were 262, 131, 65 and 37 L/ha, all made at 324 kPa. Applications of 67 postemergence grass herbicides were all made in a volume of 262 L/ha at 324 kPa. Early postemergence applications were made on July 5 when the quackgrass was 15 to 25 cm tall with three to five leaves and soybeans were in the third trifoliolate leaf stage:(V4L. Late postemergence applications of split treatment were made on July 18 to quackgrass in various stages of chlorosis and soybeans in the six trifoliolate leaf stage (V7L Cultivation treatments were made on July 18 with a two-row tractor-mounted cultivator to designated plots in conventional-till. Weed-free plots were maintained throughout the season in conventional- till with the tractor-mounted cultivator. Control evaluations of all treatments were made on August 4 and October 10 and in no-till the next spring on May 12, 1984. The two center rows of each plot were harvested for yield on October 28 with a small-plot combine. Another experiment was established in 1983 at the Kellogg Biological Station near Hickory Corners, Michigan in Kalamazoo County on a Kalamazoo loam. The area had been planted to soybeans in 1982 and had not been tilled following harvest. Preplant applications of glyphosate were made on May 14 to quackgrass that was 20 to 30 cm tall with four to five leaves. Four spray volumes were compared. These were 262, 131, 65, and 37 L/ha all made at 324 kPa. An application of paraquat at(L56 kg/ha was made on May 25 and the field was planted to 'Corsoy' soybeans with 76 cm row spacing on June 2. Plot size was four rows by 12.2 m. The experimental design was a randomized complete block with three replications. A preemergence 68 application of metolachlor (2-chloro-N-(2-ethyl-6-methyl-pheny1)-N-(2- methoxy-l-methylethyl)acetamide) plus metribuzin at 2.24 and 0.42 kg/ha was made on June 2 to control annual weeds. Early postemergence applications were made on June 22 when the quackgrass was 15 to 20 cm tall with three to five leaves and the soybeans were in the first trifoliolate leaf stage (V2L. Late postemergence applications were made on July 6 to 25 to 30.5 cm tall quackgrass with five leaves. Control evaluations were made on July 26, October 7 and the next spring on May 3. The two center rows of each plot were harvested for yield with a small plot combine on October 18 with a small plot combine. An experiment was also established in 1983 in Clinton County near Fowler, Michigan, on a Metamora-Capac sandy loam. The field had been planted to soybeans in 1982 and was chisel plowed following harvest. A preplant incorporated application of trifluralin (a,a,ot-trifluoro-2,6- dinitro-N,_N,-dipropyl-pOtoluidine) plus metribuzin at 0.84 and 0.28 kg/ha was made on June 15 for the control of annual weeds. The field was planted to 'Hardins' soybeans with 76 cm row spacing on June 17. Plot size was four rows by 12.2 m. The experimental design was a randomized complete block with three replications. Early postemergence applications of herbicides were made on July 7 when the quackgrass was 10 to 15 cm tall with three to four leaves and the soybeans were in the unifoliolate to second trifoliolate leaf stage (V1 to V3). Late postemergence applications were made on July 20 when the quackgrass was 20 to 30 cm tall with four to five leaves and soybeans were in the four 69 to six trifoliolate leaf stage (V5 to V7). Control evaluations were made on August 8 and October 8. RESULTS AND DISCUSSION Quackgrass control at the Dewitt Location from spring preplant applications of the nonselective herbicides glyphosate and SC-0224 was considerably less than that expected (Table l). The 20 to 30 cm tall quackgrass was growing in 35 to 40-cm tall wheat stubble which interfered with herbicide coverage thereby reducing effectiveness. The wheat stubble had been cut that high due to the heavy quackgrass infestation at the time of wheat harvest the previous year as the combine operator raised the header to reduce quackgrass foliage intake. SC-0224 resulted in significantly greater quackgrass control than an equal rate of glyphosate at the midseason rating in no-till and at the ealy season, late season and next spring rating in conventional-till. Moldboard plowing was beneficial only for SC-0224 as the amount of control the next spring was significantly higher in conventional till than in no-till, although control with all treatments at this time was poor. At this location, the selective postemergence applied grass herbicides were more effective in controlling quackgrass than were the non-selective herbicides (Table 2). The no-till planter and tractor tires pushed down most of the wheat stubble during planting such that 70 .cowpeowpooe Loewe mxooz —m .mm\m\miocweom pxoz .cowgeUWFooe Levee mxooz my .mw\¢w\mtcomeom one; ”cowpeow—ooe Levee mxooz m .Nw\m_\e icomeomowz “covpeoWPQQe Levee mxooz o .mm\mm\mtcomeom zzeem "wee meowpe:_e>o Foepcoo mmeemzoezo mo mopeon .pmop emcee opowu—ze m.:eo=:o op mcwoeoooe Fo>op ape—Poeoogo xm oz» we pcoeommwe zppceowewcmwm po: wee Loapop :oEEoo e zn ooZoFFow coweoo cowpeape>o :e cwspwz mceoze F-m mm e-e em a me o-e,me. ee._ eNNo-om e-e em e-e em e-o em e-e en Ne.m eeemoeaz_e e-e NN e-e e_ e-e me e-e ee ee.z meanesaz_e z_ze-.>eoo e-e mz e-e em a me e-e we ee._ eNNo-om e-e em z-e me a me e-e om Ne.N eeemoeaz_e e-e e_ o-e me e me e-o me ee._ eeemoeaz_e _Pee-oz --------- ...... ---- ...... ---e----- ................ - ....... ze;\exv mcweom pxoz comeom opee comeomowz comeom zzeem opez ecoEpemLp ezoaeeoo mmeeoxoeso .ememz we: .opezee .eNNo-om eee eeemeeezze sue: mceonzom AooZoro oeeoneroe mcveomv vapiyecowpco>coo oce Fquio: cw Fogpcoo mmeemxoezo ._ orneh .covueo_peee oucooeoEoumoe one; a edo .eopueovpeee oocooLoEoumoe apeeu n emu .coeueo.Peee zoom sue: .e;\4 m.~ «e oueeacoocou pvo eogo ooe_eu:oo mucospeoehu .eopueuv—eee Levee mzucoe ~\p a apogeevxoueee .mmxmxmnocwuem uxoz apppun—eco—uco>coo c? mco_ueuepeee cocooeoeouooe apeeo suave memo: mp one Pp.uno: c? co—ueoepeee coco «soumoe xpeeo Loewe oxoox mp .~o\o~\oncomeom ope; "moo—ueuvpeee oucoogosuumoe apeeo emcee axoo: m .Apprunocv ~o\_\o one AF—vunpecopueo>couv ~m\mp\encomeome.: ”one mco.ue=pe>o poeucou mmeeoxueoo mo moueon .umou ooze; opevupae m.ceo:=o o» ocvvgouue _o>o— quPFaeaoee um oz» we «nonopere zpuceovuwcovm we: use eouuop :ossoo e an ooze—pow eopeoe covueape>o :e cvcuvz meeoxe 71 an; on on, we wne me one we en— om .nm on pnn no pnn no ono om ~p.p speaxozuom .-o em . e o x-n me - o-u e~ en; me - a me ee.o eeeexoeuem one no o-e oe .-o em e-e Fe e-o no pnx we e-e me e-~ oe en. oe ~z.. Peeae-eee.~espe one on n one m~ eno an n an: cm an; em n an» we om.o pzuaeneouvueope o-e Fe o me o-_ es e-e Po e-o ea e-e ee e-e no o-e me 5.; em ~_._ Peeoee-eee»xepez one am one an en» mo eno no eno oo 8.“ on ens no en: oo en: es om.o pecuoEneoeaxo_ez ppeun .>=ou zne mm one mp zne on an: on .ne on .no no e cop zno no on; on ~—.p svexxozuom one we n nno co _n» on n an. —m one an n Pnn no om.o E_ezxoguom 5-; em o-e eN ¥-e eo e-F oe e-¥ es _-x Fe e co, v-9 me e cop ~..~ Phase-eeee~eepa on. me n xno co En; me n gnu on one am n one no om.o pauoaneomvneope one am on; no ono mm e we ene co. e we e cap on, .o e cop NP.p PzzuoEneoezxopez en, me Eng am one on one mm en: om en: om eno me one am one am om.o Pzzuosneoezxopez . pp,» oz nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnunnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn nezxoan B.Pew we; eee. u.Pem eeo eee oepem we; eem . no.“ accuseeeep moveem uxoz. comeom owe; someone»: apoeucoo mmegmxueaa .eummp we: .uuvzoo .meopueu.peee appem eee .oocooeosoumoe ouep .oocooeosoumoe apeeo eoepeee moe+uveeoz omega oucoogueoumoe zu.: meeoazom Aeoxope eeeoaepoe o:.gemv ppvunpeco.uco>cou nee pp—unoc e, posacoo mmeeoxueoo .~ opae» 72 interference with herbicide coverage was not a factor with postemergence applications. Midseason control evaluations indicate that early postemergence applications to 10 to 15 cm tall quackgrass was significantly higher for each herbicide in no-till than similar applications in the spring-plowed conventional-tilled soybeans. The split applicationscfl’each herbicide treatment hiconventional-till resulted in significantly higher midseason quackgrass control than did the early postemergence applications. 'However, in no-till, except for sethoxydim, there were no significant differences in control between early postemergence and split applications. Therefore, at this location spring tillage influenced control. Spring plowing disrupted the rhizomes and dispersed fragments at different depths such that shoot emergence evidently was not uniform and a second or later application was necessary to control later emerging shoots. However, in no-till, the rhizomes were able to initiate shoot growth more uniformly'such that most shoots were controolled with a single early postemergence application. By late season, very good quackgrass control was maintained in no- till with all applications of haloxyfop-methyl. No significant differences in control were seen between 0.56 and 1.12 kg/ha except with the split application where the higher rate provided greater control. In conventional-till, the late postemergence and split application of 0.56 kg/ha of haloxyfop-methyl provided significantly greater quackgrass control than the early postemergence applications. lirate effect was observed with the early postemergence application 73 where 1.12 kg/ha of haloxyfop-methyl resulted in significantly greater control than 0.56 kg/ha. Split and late-postemergence applications of fluazifop-butyl were also more effective in late season control in conventional-till than the early postemergence applications. However, in no-till there were no significant differences in control between time of application. No sinificant differences in control were observed between (L56 and 1.12 kg/ha. Sethoxydim was less effective than either fluazifop-butyl or haloxyfop-methyl, particularly in the later evaluations. As with the other herbicides, no significant differences in control were observed by late season between the different times of application in no-till, although the late and split applications were more effective in conventional-till. Particularly poor late-season control was obtained with early postemergence applications in conventional-till. Several treatments resulted in moderately high levels of control the next spring approximately 9.5 months after application, particularly the late-postemergence and split applictions of haloxyfop- methyl and fluazifop-butyl in conventional-till. Evidently the undisturbed no-till generated more new rhizomes and hence more regrowth the next spring than did the moldboard plowed system even though tillage did not greatly affect infestation levels the year in which tillage was performed. Due to the heavy thatch layer of the wheat stubble and desiccated qackgrass at the time of planting, an uneven soybean stand was 74 established as the soybean seed was not able to consistantly drop into the seed furrow. Therefore, only the conventional-till portion was harvested and yield data are shown in Table 3 for all treatments. Despite rather poor season-long control obtained by the non-selective and sethoxydim treatments, all treatments resulted in yields significantly greater than the untreated plots. Evidently, the early season control was adequate. Highest yields tended to come from late postemergence and split applications which reflected extent of quackgrass control. Herbicide treatments enabled an approximate three- fold yield increase over no treatment. The East Lansing 1982 location, also was moldboard plowed in the spring; however, this location was planted with soybeans in 24 cm rtnv spacing compared to 76 cm row spacing at the Dewitt location. Unlike the Dewitt location, there was no significant difference between quackgrass control obtained by early postemergence and split applications fin~f1uazifop-butyl and sethoxydim (Table 4). Although split application resulted in significantly greater control, split and early postemergence applications of haloxyfop-methyl did not differ in the magnitude of control at this location that they did at the Dewitt loaction. High levels of control were also obtained from early postemergence applications of DPX-Y6202. Evidently, the narrow row spacing enhanced control of the single early postemergence applications by interfering with the later emerging shoots. Late postemergence applications were lower in midseason quackgrass control than early postemergence and split application possiblychmzto interference in 75 Table 3. Soybean yields in conventional-till (spring moldboard plowed) soybeans with non-selective and selective postemergence grass herbicides. Dewitt, Mi; 1982a. b Soybean yield Treatment Rate Preplant EPC LPd Split ------------------------ (kg/ha)----------—-------- GIYPhosate 1.68 1199 b-c - - _ Glyphosate 2.52 1317 b-e - - - SC-0224 1.68 1734 c-j - - - Haloxyfop-methyl 0.56 - 1530 b-h 2223 j 1833 e-j Haloxyfop-methyl 1.12 - 1760 d-j 1946 h-j 2174 i—j Fluazifop-butyl 0.56 - 1392 b-g 1580 b-h 1789 d-j Fluazifop-butyl 1.12 - 1790 b-j 1535 b-h 1696 c-j Sethoxydim 0.56 - 1258 b-d 1798 d-j 1715 c-j Sethoxydim 1.12 - 1360 b-f 1707 g-j 1505 b-h No treatment - - ........... 555 a ____________ aMeans followed by a common letter are not significantly different at the 5% probability level according to Duncan's multiple range test. bSelective postemergence grass herbicide treatments contained crop oil concentrate at 2.3 L/ha, with each application. CEP dLP Early postemergence application. Late postemergence application. 76 .cowpeowpeee oucooeosopmoe ope; .cowpeowpeee oocooeoeopmoe Apeem ezm emv .cowpeoVFeee zoeo gum: .ez\4 m.~ we opeepcoocoo Pwo eoeo oocwepcoo mucoEpeoep Fro Poepeoo mmeeoxoeoo mo moves a .pmou emcee orewupze m.:eo=:o op mcvoeoooe Fo>op zuwpwoeooee em on» we pcoeommwo Appceowewcowm po: wee eoppop :oEEoo e An oozoppom voweoe coepe:_e>o :e :wzpwz mceoze ene Fe eno me one em e-e me ene me one _e ee.o eeezxoeoem ene _e . one _e z-o me n one me ee.o eeezxoeeem Ene Fe e-x me one ee en? mm o-e em ene ee ee.o ereeneoe_ee=_e en; we . ene we zno we - one me ee.o _ze=eneoewNee_e one we e-e _e fine ee xne em o-e Fe ene em ee.o Nome>nxee Fne ee - ene ee en? em - ene em em.o Nome>nxee on, mm 0-5 em ene ee x em e-e we eno ee ee.o _zeerneeezoneI 0.: em 0 em ene ee xne em eno me Lno we em.o _zeeee-eeezxeeex -nn ..... -nn-n----nnnnnnnn-n--nn-ennn--nnnnnnnnnnnnnnnn ..... n--- zee\oxv “weem eed eee oe_em eed eee eoee ooeeEoeoee comeom ouez , , , n . comeommti ..opoepcoo mmeeoxoeoo .emmm_ we: .ocwmcez poem .mcoepeoweeee pwpem oce .oocomeoeopmoe ope_ .oocomeosoumoe zPeeo me oowpeee moowowoeo; mmeem mocooeoeopmoe zpwz meeonzom scenZoeeec .Aoozope oeeoQUFoE ocweemv P—wunpecoepco>coo cw Foeucoo mmeeoxoezo .o oFoe» 77 coverage due to the soybeans in narrow rows. However, sufficient phytotoxicity resulted to enable improved control by late-season evaluations. All treatments resulted in significantly higher yields than the untreated control, although no significant differences were found between treatments (Table 5L Some soybeans wereiuuiover with the tractor during late postemergence applications due to the narrow rows and the size of the soybeans at that time. However, complete recovery was observed and this did not affect yield. At the East Lansing 1983 location, postemergence grass herbicides were applied to quackgrass under no-till and conventional-till situations, however, the conventional tillage was fall moldboard plowed and the no-till was in a quackgrass sod. Very high levels of quackgrass control were obtained season-long with all rates of haloxyfop-methyfl and DPX-Y6202, even with(L28 kg/ha which was not applied in the 1982 experiments (Table 6). There were no significant differences in control due to tillage rate or time of applications with these two herbicides. There were no significant.effects.on control withiL42 and(L56 kg/ha of fluazifop-butyl due to tillage or tinua of application. However, with 0.28 kg/ha, single early postemergence applications in no-till resulted in significantly lower quackgrass control than split applications or single applications of 0.42 and 0.56 kg/ha. Applications of sethoxydiniinere generally uneffective in controlling quackgrass at this location. By late-season, particularly 78 Table 5. Soybean yields in conventional-till (spring moldboard plowed), narrow-row soybeans with postemergence grass herbicides applied as early postemergence, late postemergence, and split applications. East Lansing, Mi; 19823. Soybean yields Treatment Rate EPC LPd Split ------------------------ (kg/ha)----------------------- Haloxyfop-methyl 0.56 2455 b-c 2950 b-c 2860 b-c Haloxyfop-methyl 0.84 2836 b-c 2486 b-c 2321 b-c DPX-Y6202 0.56 2705 b-c - 2548 b-c DPX-Y6202 0.84 2354 b-c 2252 b-c 2163 b Fluazifop-butyl 0.56 2426 b-c - 2543 b-c Fluazifop-butyl 0.84 2791 b-c 2400 b-c 2724 b-c Sethoxydim 0.56 2793 b-c - 2745 b-c Sethoxydim 0.84 2682 b-c 2105 b 2906 b-c No treatment - -------------- 774 a ---------------- aMeans followed by a common letter are not significantly different at the 5% probability level according to Duncan's multiple range test. bAll treatments contained crop oil concentrate at 2.3 L/ha, with each application. CEP Early postemergence application. LP Late postemergence application. 79 ”coppeoVFeee oocomeosouwoe zoeo Loewe mxoo: o .mm\o\mn=omeomopz .cowueovpeee zoeo new; .ez\4 m.~ we oueeucoocoo Peo eoeo overeucoo mucosueoeu ppo _oeueoo mmeeoxoeoo mo moueo a .umov ooze; o_e_p—:E m.:eo==o ou.ocwooeooe Fo>op zuwp_neeoee am me» we pcoeoeeeo z_u=eoeeecorm no: oee eopaop eoesoo e en oozoppow ooeeoe copueape>o ce owner: meeoze wno em zno mm one om one op one me one no xne on .no no om.o eeoxwozuom ono me one on one om e o xno um one on one mm one em om.o seozxozuom wno oo eno oo one mp one e one we zna No zne co one Nu ~o.o seozxozuom one om Pno no onn we on? me en_ mm onz mm on: mm enx mm om.o exuoeneoepeeope 5-; ee e-e Ne en? me en? me e-. me One me one No e-“ we Ne.o Pepeeneeeeees_e x-o me ene No one me one me ene Ne sno me one we e-e we e~.o onea-eeee~eapa on: mm o no one mm onz mm a cop one no one we uno mo om.o No~o>nxeo one we on: em on: we on? mm one em on: om one mm one no ~o.o ~o~o>nxeo one em one mm on: om on: we unm mm on: mm uno mm one no m~.o ~o~o>nxeo one we one am onE em onn ee one no «no No one ea uno mm. om.o _zzuo5neoezxo.ez on: cm on: mm one em one mm uno mm mno No uno mm mno No No.0 PzeuoEneowzxopez one No one me one oe ene oe one No one he a-e me a-o Ne e~.o .eeeee-eee»xope: nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnannnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn Aez\oxv Sweem tweeem, peeem eeeeem ee_em eeoezm eweem e_oe_m apex beeeEHeeee Freon.>cou Fqunoz Ppeun.>cou Prwpnoz comeom one; comeomomz n Poeucoo mmeemxueoo oocooeosoumoe ewe: oceonxom Aoozope ogeonopos Ppewv ppvunpecoeuco>coo oce Ppmuno: cw Foeueoo mmeeozoeoc .emmop we: .ocemcee «new .mco_oeowpeee uwpem so opocem me oorpeee moowovneoz omega .e e_eee 80 in no-till, very little herbicidal effect was observed. Unlike spring moldboard plowing, fall moldboard plowing seemingly does not result in differences in quackgrass control between single early postemergence and split applications. Lack of major rhizome disruption in the spring during shoot initiation enables a relatively uniform growth stage for control with single applications of postemergence grass herbicides in both no-till and fall moldboard plowed situations. The only time an advantage1x>split applications was observed was with the(L28 kg/ha rate of fluazifop-butyl in no-till and with (L42 kg/ha of sethoxydim. Here the advantage of split applications is due to the fact that these rates are too low to be applied in one application and the multiple doses are more phytotoxic to quackgrass. Despite varying levels of quackgrass control, there were generally no significant differences between treatment yields either in no-till or conventional-till (Table 7). Except for the single application of 0.56 kg/ha of sethoxydim in no-till and single and split applications of 0.42 kg/ha of fluazifop-butyl, all treatments had significantly higher yields than no treatment. It is felt that the aforementioned sethoxydim treatment did not differ in yield from no treatment as a result of lack of sufficient quackgrass control. However, other factors must be responsible for the fluazifop-butyl treatment not being significantly different in yield than no treatment since relatively high levels of quackgrass control were obtained season-long and no soybean injury was observed. Tillage did not affect quackgrass pressure in untreated plots as near identical yield means were obtained in no-till and conventional-till. 81 .coepeoeeeee coeo ope: .ec\o m.m we opeepcoocoo _eo eoeo oocweucoo mpcoEpeoeu FP< a .pmop emcee oFeepeos m.ceoc:o ow oceoeoooe Fo>op ape—eoeooee om oz» we pcoeoeeeo xepceoeeecoem poc oee eoppop coEEoo e en ooZoFPoe mceoze nnnnnn -ne eeeennn--n-n -nnnnnne Neoennnnn--n . oeeeoeeeo oz o-e moeN one eeee o-e Nome o-e meme ee.e ceeeXOooem one meee o-e NmeN one come one _eem mm.e eeeexeooem o-e meoe one meow one Poem one meme No.0 eeeexeooem one meme ene meow one meom one meme mm.e eeoemneeeeNeeeo one memo one meee one eeem o-e Neon No.0 _eeeeneeeeNeeee one eNeN o-e meme o-e Nmem o-e Nmee em.e zooeeneeeeeee_o one come one come one moeN one NFNm mm.e Neemenoee o-e come one oeee one emoe o-e eNeN No.0 Nemmonoee one come one meme o-e meem one em_e eN.e Nemmonoee ene meow e-e emmN one eNeN one meem em.e eeooee-eeeexe_ez one meme ene memo o-e mmeN o-o eeem No.0 eeoeecneeeexe_eo o-e moem ene memo o-o eeem one eoem em.e eeooecneoeexeeeo --n--nn-n-n---n-nnnn--nn--n-nn--zeo\eoo-nnnnnnnnn-n-n .............. n-n-nn eeeem aeecem oeeem eeecem ooeo eoeeEeeeee reepn.>cou reepnoz oPoex ceooxom .emwm_.mez .mcemceo“mew...mcowoeow_eee pepem eo ochem me ooepeee moowowoeo; mmeem oocomeosopmoe ope: mceooxom Aoozope oeeoooeoe Peeev Ppepn—ecoepco>coo oce P—epnoc cw mopoex ceooxom .n mpnep 82 Despite high levels of season-long quackgrass control from several of the postemergence applied herbicide treatments, evaluations of regrowth the next spring in no-till indicate poor control with all treatments (Table 8L. Since vegetative growth of quackgrass is so prolific it is unlikely that any treatment would provide satisfactory control through a second season and it is likely that retreatment is necessary. A series of treatments was established in the conventional-till portion of this location where a mechanical cultivation was substituted for the second herbicide application of a split treatment. The control data in Table 9 indicate that a cultivation is as effective as a second application of herbicide. Late season evaluations showed that early postemergence plus cultivation treatments with sethoxydini were significantly better in quackgrass control than early postemergence or split applications. A cultivation also significantly increased the control of early postemergence applications of fluazifop-butyl. Soybean yields from cultivation treatments were not significantly different from early postemergence or split applications of treatments and there were no significant differences in yield between herbicides. All treatments resulted in significantly higher yield than no treatment (Table 10). Therefore, with all herbicides, cultivations enabled comparable control with half of the total rate of applied herbicide. Fall applications of haloxyfop-methyl and DPX-Y6202 resulted in high levels of quackgrass control the following spring in no-till, but only fair control in conventional-till (Table 11). Perhaps moldboard 83 Table 8. Subsequent season quackgrass control in no-till soybeans with post- emergence grass herbicides as single or split applications. East Lansing, Mi; 1983a. Quackgrass controlb Treatment Rate Single Split (kg/ha) --------- % --------- Haloxyfop-methyl 0.28 43 a-k 37 a-j Haloxyfop-methyl 0.42 47 b-m 50 c-m Haloxyfop-methyl 0.56 47 b-m 30 a-i DPX-Y6202 0.28 ' 57 d-m 50 c-m DPX-Y6202 0.42 37 a-j 33 a-i DPX-Y6202 0.56 45 a-l 43 a-k Fluazifop-butyl 0.28 7 a-c 27 a-g Fluazifop-butyl 0.42 27 a-g 45 a-l Fluazifop-butyl 0.56 40 a-g 50 c-m Sethoxydim 0.42 10 a-c lO a-c Sethoxydim 0.56 7 a-c 13 a-d Sethoxydim 0.84 3 a-b 3 a-b aMeans followed by a common letter are not significantly different at the 5% probability level according to Duncan's multiple range test. bQuackgrass control evaluated on 5/12/84, 41 weeks after early postemergence applications. .coeue>wp—:o moee coepeoePeee oocooeoEoumoe apeem n ._:u + emo .coepeoeeeee oocooeoEopmoe xpeem n emo .coepeoweeee coeo cow: .ec\o m.~ pe oueepcoocoo Feo eoeo ooceeucoo mpcoEpeoew epFeeo eopee moooz o_ .mm\op\o_ncomeom opeo mmcoepeow—eee oocooeosoumoe zeeeo eopee moooz o .mw\o\mncomeomoez ”wee mcowpe:_e>o Poepcoo mmeeoooeoo eo mopeao .umop emcee oeewu_:e m_ceoc:o ou oceoeoooe _o>o_ zuepeoeooee om ocp we ucoeoemeo epoceoeeecoem poc oee eouoo— coEEoo e on oozoeeoe ooeeoe coepezee>o ce cecpez mceoze 84 ene.men one oe one ee. cone me one me one we No.0 eeeexecoem Ene me - n one em n . eN.e eeeoxeooem e-o me one mm e-o Nm _ne me one oo o-e mm eN.e _eoee-eoee~ee_e en; me n n Eno Ne n n ez.e eeoee-eeeeoeeee e-e ee e._ no e-o me ene me ens ee 5-; we eN.e Nemmonxee cnc we - n cne me n n ee.e Nommonoee e-e oe ene Ne ene me an; me e.; Ne 5.: Ne e~.o _eooee-eoeexe_ez ene me n n one me n - e_.e _eoerneoeexeeeI nnnn-nn-nnnn--n--nnnnnnnnnnnnnnnonnnnnnnn--nnnn--n---- nnnnnnnnnn zeo\eov e.eeo + em . oeoem , eem, e._eo + em oe_em .eem eoeo oocecoeeee comeom opeo. comeomoez neoepcoo mmeeoooeoo .eeee_ we: .eeeeceo omem .mpcospeoep coope>ep_:o mope oocomeoEopmoe xeeeo oce pw—em .oocooeoeopmoe Apeeo me ooweeee mooeowoeo; mmeeo oocooeosopmoe ope: mceooxom Aoozoee oeeooopoe Feeev FFepnPecoepco>coo ce Foepcoo mmeeoooezc .m o_oee 85 Table 10. Soybean yields in conventional-till (fall moldboard plowed) soybeans with postemergence grass herbicides applied as early postemergence, split and early postemergence plus cultivation treatments. East Lansing, Mi; 1983a. Soybean yield Treatmentb Rate EPc Split EP + Cul.d ------------------------ (kg/ha)---------------------- Haloxyfop-methyl 0.14 - - 3006 b Haloxyfop-methyl 0.28 2595 b 2903 b 2878 b DPX-Y6202 0.14 - - 2646 b DPX-Y6202 0.28 2826 b 2800 b 2878 b Fluazifop-butyl 0.14 - - 2852 b Fluazifop-butyl 0.28 2826 b 2929 b 2672 b Sethoxydim 0.28 - - 2852 b Sethoxydim 0.42 2723 b 3006 b 2954 b Cultivated weed-free - ------------ 2749 b -------------- No treatment - ------------ 1773 a -------------- aMeans followed by a common letter are not significantly different at the 5% probability level according to Duncan's multiple range test. bAll treatments contained crop oil concentrate at 2.3 L/ha, with each application. CEP = Early postemergence application. dEP + Cul. = Early postemergence application plus cultivation. 86 .coppeoppeee ooeo opp: .ec\o m.m pe opeepcoocoo Fpo eoeo oocpepcoo mpcoEpeoep ppo mmeeoooezo eo mopeo n .pmop oocee opepppos m.ceoc:o op oceoeoooe _o>o_ e en oozoFFoe oopeoe coppeope>o ce cpcppz mceoze one om e m one me one me e o one o eN.o mmme eeeexoooom eno mm one em _ne em one om one em one em eN.o oee.o peoeeneoeeeee_e one Ne one No one Ne one me one om e ee e~.o oem.o .moweenoee 0.: ee ono me one oe one me o co e ee em.o mmme _eopocneoeexo_e= oocomeosopmoe Apeem ”Ppee one op e 0 one me e m o co e me mm.e .Nemeonxee one e_ e 0 one e_ e m o mm e we mm.e zeopoEneoeexopeI eoeoeee ppee -nnn----n--nnn--n---nnnn-nnnnnn--n--n--ne-nnnnnnnnn-----n-n---n----nnnnnnnnnn zeo\eoo _peon.>eoo __eonoz ppepn.>eoo .pppnoz _ppo-.>eoo p_eonoz opeo oococoeoep comeom opeo comeomopz oceeem opoepcoo mmeeoooeoo .emee_ oez .eeeeceo poem .moopoeoeoz mmeem oocooeoEopmoe eo mcoppeoppeee mocooeoEopmoe zpeeo oce Fpee opp: mceooeom AooZope oeeooopos ppeev Peppnpecoppco>coo oce peppnoc cp Foepcoo mmeeoooezo .pp opoee 87 plowing six weeks after a fall application reduced the phytotoxicity of herbicides by reducing translocation to rhizome fragments. However, despite high levels of spring control, very poor control was observed in both no-till and conventional-till at the midseason and late-season evluations. This was again due to the prolific growth of quackgrass that was not treated within the growing season. Early postemergence applications of haloxyfop-methyl and DPX-Y6202 following fall applications resulted in excellent, season—long quackgrass control. Therefore, fall applications of these herbicides was not advantageous to postemergence applications within a growing season. Poor quackgrass control in the spring was observed with fall applications of fluazifop- butyl and essentially no spring control occurred with fall applications of sethoxydim. Fall moldboard plowing also reduced effectiveness of fall applications of fluazifop-butyl. Early postemergence applications of fluazifop-butyl following fall treatment were not effective as were similar treatments of haloxyfop-methyl and DPX-Y6202 in season-long control of quackgrass. Very low levels of quackgrass control were obtained from sethoxydim applied in this manner. However, despite varying levels of quackgrass control, all treatments resulted in yields that were significantly higher than no treatment except for the fall application of DPX-Y6202 in no-till (Table 12). Even though very poor control was obtained with sethoxydim, control was sufficient at the critical period of soybean growth so as to enable the observed increased yield. The highest yield was from fall plus spring applications of haloxyfop-methyl. Table 12. Soybean yields in no-till and conventional-till (fall moldboard plowed) soybeans with fall and early postemergence applications 88 of postemergence grass herbicides. East Lansing, Mi; 1983a. Soybeanyyield Treatmentb Rate No-till Conv.-till ------------------- (kg/ha)-------------------- Fall applied Haloxyfop-methyl 0.56 2492 b-e 2980 b-k DPX-Y6202 0.56 2364 a-c 2698 b-i Fall; Earlyypostemergence Haloxyfop-methyl 0.56; 0.28 3520 j-k 2620 b-h DPX-Y6202 0.56; 0.28 3314 f-k 2672 b-h Fluazifop-butyl 0.56; 0.28 2829 b-k 2826 b-k Sethoxydim 0.56; 0.28 2492 b-e 2878 b-k No treatment - - 1747 a 1773 a aMeans followed by a common letter are not significantly different at the 5% probability level according to Duncan's multiple range test. b application. All treatments contained crop oil concentrate at 2.3 L/ha, with each 89 Fall and spring applications of nonselective herbicides were also made to quackgrass at this location. Fall applications of both glyphosate and SC-0224 resulted in high levels of quackgrass control the following spring in both no-till and conventional-till (Table 13L Unlike the fall applications of postemergence grass herbicides, moldboard plowing after applications did not reduce control observed the following spring. Also, unlike the postemergence grass herbicides, fall applications of non-selective herbicides resulted in relatively high levels of quackgrass control the entire following season. High level season-long control with spring applications was obtained only in no-till. Evidently the fall moldboard plowing disrupted the rhizomes and dispersed fragments over several depths and not all shoots were emerged at the time of the spring preplant application. This is consistant with the findings of Sprankel et al.(14, 150 and Behrens and Elakkad (3L Therefore, under this cultural system it may be beneficial to utilize postemergence grass herbicides which are applied later in the season when the shoots from deeper rhizome fragments have emerged. However, all non-selective herbicide treatments resulted in significantly increased yields over no treatment and were comparable to those obtained with postemergence grass herbicides (Table 14). Spring applications of nonselective herbicides glyphosate and SC- 0224 were applied in the no-till portion of this experiment at a rate of 1.68 kg/ha in four different spray volumes. Generally, spray volume did not influence control with this rate of these herbicides (Table v-vozz" .mw\o—\o_ncooeoo opeo omw\o\mncooeooopz omw\m_\mnocpeem ”wee ocoppeope>o Foepcoo ooeeoooeoo mo oopeo a .poop emcee opepppee o.ceoc:o op ocpoeoooe po>op app—poeooee om ocp pe pcoeomwpo xppceopmpcopo poc oee eoppop coEEoo e on oozo—Foe oceoze eno oe ono mo eno em one on n n oe.o ewwonoo o-e me one me o-e ow ono we - n oe._ ooeeooeepe ooppeee mcpeem no one we one we e-e oo one oo o me e mo wm.w ewwo-om o. ono mo on; me one we 5-; ee o oo o mo oe._ ewwonoo o-e eo o-e oo e-e oo e-e oe e we e mo wm.w ooeoooeepo o-c oo one we eno we one ee o oo o mo oo._ opeoooeepe eoe_eoe epee -n-nn---nnnnn-nnnn-nn--n ....... nn--nn--o ..... -nnnnn-n---n--- .......... nnn--- zeo\eoo ppeon.>eoo Fpeonoz Peep-.>eoo _eepnoz epeon.>coo p_epnoz ooeo oeoEoeoep cooeoo opeo cooeoooez ocweem nZoepcoo ooeeoooeoo .emmmp we: .oceoceo poem .oNNOnum oce opeooseepo mo ocoppeoppeee ocpeeo oce Free opp; oceooxoo Aoozope oeeooopoe P—eev ppppnPecoppco>coo oce Ppppnoc co Foepcoo ooeeoooeoo .m_ opoep 91 Table 14. Soybean yields in no-till and conventional-till (fall moldboard plowed) soybeans with fall and spring applications of glyphosate and sc-0224. East Lansing, Mi; 1983a. Soybeanyyield Treatment Rate No-till Conv.-till -------------------- (kg/ha)-------------—----- Fall applied Glyphosate 1.68 3520 j-k 2800 b-k Glyphosate 2.52 3520 j-k 2903 b-k SC-0224 1.68 2852 b-k 2800 b-k SC-9224 2.52 3109 c-k 2980 b-k Spring applied Glyphosate 1.68 3494 j-k 2698 b-i SC-0224 2.52 3417 j-k 2877 b-k No treatment 1747 a 1773 a aMeans followed by a common letter are not significantly different at the 5% probability level according to Duncan's multiple range test. 92 15). Midseason control with SC-0224 from the 37 and 262 L/ha volumes was significantly lower than that from the 131 L/ha volume, although by later evaluations no significant differences were observed. Quackgrass control from both herbicides was comparable as were the soybean yields. Only fair control of quackgrass was observed the next spring or one year after application and retreatment may be necessary. Several rates of glyphosate were applied in four spray volumes in a no-till situation at the Kellogg Biological Station in the spring of 1983. However, this no-till field had been in soybeans the previous season rather than in a quackgrass sod as in the East Lansing location. Generally, the highest control was obtained with the three highest spray volumes of each rate (Table 16). Although high levels of control were obtained with 37 L/ha, this volume may have been too low for adequate coveratecflithe thick stand of quackgrass at this location. The (L84 kg/ha plus surfactant rate was as effective as the two higher rates. Surfactant did not influence control with 1.68 kg/ha. All treatments resulted in yields which were significantly higher than no treatment and there were no significant differences between treatment yields (Table 17). Complete or near-complete control of quackgrass was observed a year after application with all rates applied in the three highest spray volumes (Table 18). High levelscfiicoontrol were obtained with the 37 L/ha volume. It is unlikely that retreatment of quackgrass with any herbicide would be necessary. 93 .coppeoppeee eopee ooooz mm .ow\mp\mnocpeeo pxoz ”coppeoppeee eopee ooooz _N .mm\op\opncooeoo opeo ”coppeoppeee eopee ooooz Pp .mm\o\mncooeooopz "oee ocoppeope>o Poepcoo ooeeoooezo mo oopeoo .poop emcee opepppoe o.ceoc:o op ocpoeoooe po>op xppppoeooee om ogp pe pcoeoeepo appceopepcopo poc oee eoppop coEEoo e on ooZoFFoe oopeoe coopeope>o ce cpzppz oceoze e eoe— pcoEpeoep oz Enp momm Enc mo eno mm on; we mom wo._ ommonum Eno momm Enw me e mm cno mm _m_ wo.p oNNOnom E momm Eno em eno om Enp mm mo wo._ oNNOnuo En» wwmm Eno oo eno we on; ow em mo._ oNNOnom Eno eeem one me eno me one we wow oo; ooeeoeebo cno ooww Eno oo to oe co me :2 oo; opeooeebo Eno me; an; 2 one we one we oo oo; ooeeooebe Enw moom Enp Ne eno mm onc mm em wo._ opeoocex—w zefieoo -n .......... - ......... o. .................... 3:: oefieoo opop> ocpeeo pxoz cooeoo opeo cooeooopz .Fo> xeeem opem pcospeoep ceooxom poepcoo ooeemooeoo .emwm_ op: .ocpoceo poem .ooE3Po> xeeeo eooe cw owe—eee ommonom oce opeoocexpo opp: oceooeoo ppppnoc co oopopz ceooxoo oce poepcoo ooeeoooeoo .m_ opoeh 94 .mw\e\o—ncooeeo epeo ”coppeoppeee eooee ooooz op .mo\ow\eneoeeooeez ”eee ocoppezpe>e Poepcoo ooeeoooeoo mo oepeo .zceeeoo PeopEecu coe>ecu u eenxo .coppeoppeee eepee ooeez pm a .poep emcee e—epp—oe o.ceoc:o op ocpoeoooe Fe>ep xppppoeooee om ezp pe pceeeoepo xppceopepcopo poc eee eeppep coEEoo e on oezoppoe oopeee coppezpe>e ce cocppz oceeZe o oo_ eoop o oo_. ono oe p oop pno oe _ oop one oo wm.w eoemooeepo o oop one oe e oop ono me p oop pno oe pno oe o-e oe oo.p epeoooeepo o oop ene me o ooo eno oe pno ee _-o oe _ oop ene oo z>o>o ow\_ + oo._ eo-o + ooeoooeepo one me one oe o oo_ one mo o-p me p-o oe p-o oe e-e oo z>\>o ow\_ + eo.o ooono + ooeeooeepe -----n----n--n-n---nnn----nnn-nnnon----n-nnnn-nn-nn-----nnnnnnnnnnn- zeo\eoo eoeo.wow ...npop_ _nmo_ enem eo\o woe» -pmp -mo nee ooeo ococpeeep cemmmm mum.— :Ommmmwwz . . . opoepcoo ooeeoooeso .emoep op: .copoeoo peoeeopope oooppeo .er:_o> xeeeo eooe cp oeppeee epeoozezpo cppz oceeozoo peppnoc co Foepcoo ooeeoooeso .o_ epoep 95 .mceeEoo peopeeem coe>ezo n eenxo .poep emcee epepp—oe o_ceoc:o op mcpoeoooe pe>ep zppppneooee om ezp pe pceeeeepo mppceopepcmpo poc eee eeppep coEEoo e on oezoppoe oceeZe e moo. e;\o New epopo eeooeoo pceEpeeep oz ono mewp one womp pno womp one meme wm.w ooeoooeepo one meme one poop pne opop pne oemp mo._ ooeoooeeoe _ne oeop _-p eeop one womp o-e ooop z>\>o owop + mo._ Keno + ooeoooee_e one eoop _-o ooop pne ooep pne peep z>\>o ow\_ + om.o oeeno + ooeoooeepo ---n--n-----nnn-n----n-nnn-nnnzeo\eoon-----n---n-n-n--------nnn-nn-nn-n--n- wen_mp nmo -om opeo oeoEoeoep Peopmopopm mmoppeo .emoep opz .copoeoo .er:_o> meeeo eooe cp oeppeee epeooeex—m opp; oceeoxoo Peppnoc cp oope a ceeomom Hep epoee 96 .mceesou peopsecu coe>ezo u eenxo .pceEpeeep eo coppeoppeee eepee ooeez Fm .ow\o\m co oepezpe>e poepcoo ooeemooeooo .poep emcee eFepppzs o.ceoc:o op mcpoeoooe Fe>ep mpeppoeooee om ezp pe pceeeewpo xppceooepcmpo poc eee eeppep coEEoo e an oezoP—oe oceeze o-e oe e-e oe A o oo_ o me wm.w ooemooeepo one me o oo_ o-e oe 5 mm oo.p ooeeoooepo e ee one me o ee en; em Asoso ow\p + oo._ oe-o + ooeooooepo one me one me one me 5 mo z>\>o ew\p + om.o oneno + ooeoooeepo n---n--n---nnn---nn-n--on--n---n--n--n----nn-n-- zeo\eoo eo\o wow -pmp -oo -om ooeo oeoEoeoep o—oepcoo ooeemooezo .oeszpo> meeeo eooe cp oeppeee epeoozempm zpoz oceeomoo .emmep we: .eoooeoo peopeopoee eeoopoo ppppnoc cp poepcoo ooeemooeeo cooeeo pcezoeoozo .w_ epoep 97 The type of no-till system evidently influenced the duration of control with the non-selective herbicide glyphosate. At the East Lansing location, only fair control was observed a year after spring applications to quackgrass growing in a dense sod which had not been cropped the previous year (Table 15). However, at the Kellogg location excellent quackgrass control was observed a year after applications to quackgrass growing in a field which had been tilled and planted to soybeans the previous year. Postemergence grass herbicides were applied as early postemergence late postemergencem and split applications to quackgrass in no-till soybeans at the Kellogg location and control data are shown in Table 19. Generally; the early postemergence and split applications were more effective in quackgrass control than the late postemergence applications. Quackgrass was 20 to 30-cm tall at the time of late postemergence applications and was more difficult to control at this growth stage with the rates indicated. In addition, the larger soybean plants at this time reduced herbicide coverage of quackgrass. Despite the relatively high levels of quackgrass control at the midseason evaluation with early postemergence and split applications, by the late season evaluation only fair control was obtained with applications of haloxyfop-methyl, DPX-Y6202 and fluazifop-butyl. Poor late-season control was obtained with obtained all applications of sethoxydim. There were no significant differences in control between the two different rates of each herbicide. oppppoeooee em eee 98 mocoppeoppeee eocemeeeepooe mpeee eepee ooeez m .mw\om\encooeeoopz .ocoppeoppeee eocemeeEepooe epeo .coepeop—eee eocemeeEepooe mpeem eoe em o .coppeoppeee ooee opp: .eo\o m.m pe epeepceocoo Foo eoeo oecpepcoo opceEpeeep ppe Foepcoo ooeemooezo eo oepem o .poep emcee epepp—zs o.ceoc:m op mcpoeoooe pe>ep pe pceeeeepo mppceopepcmpo poc eee eeppep coEEoo e mo oezoF—oe oopeee coppeope>e ce cooppz oceeze one up. one e one mm one me one no ono om ow.o Epomxoopem one e e 0 one em eno me e mm eno No om.o Epomxoopem one om one ew p-e wo one ee one me one oe om.o empeoneoeeweeoe eno mm one o— e-e eo one we e oo eno me mw.o peoeo-ooeeweepe on; me ono om ono me pnn em ono mo ono mm om.o Nomo>nxem cnm we eno mm Fne oo eno mm ono me one no w~.o ~o~o>nxeo cnm me one mm ono me F oop ono me one mm om.o peopeEneoemxopez pnm co mno No ono me one mm eno no one mm mm.o FmopeEneoemone: ----- ..... --------------------o-------------------- ..... ---- oeooeoo oppoo oeo eee pppeo oeo eee eoeo ooeeEoeeep cooeeo epeon cooeeoopz opoepcoo ooeemooeeo .emwmp we: .coppepm peopmopopm mmoppeo .ocoppeoppeee pppeo oce eocemeeeepooe epep .eocemeeEepooe mpeee oe oeppeee oeopopoeeo ooeem eocemeesepooe opp; oceeomoo Peepnoc co poepcoo ooeemooeoo .mp epoep 99 All early postemergence and split applications of haloxyfop- rnethyl, DPX-Y6202 and fluazifop-butyl and those of the 0.84 kg/ha application of sethoxydim resulted in yields which were significantly higher than no treatment (Table 20). Late postemergence applications of 0.56 kg/ha of haloxyfop-methyl, 0.28 kg/ha of DPX-Y6202, 0.28 and (L56 kg/ha of fluazifop-butyl,(L56 and(L84 kg/ha of sethoxydim and early postemergence and split applications of (L56 kg/ha of sethoxydim did not result in yields which were significantly different than the untreated control plots. This occurred in spite of control evaluations, although poor, that were greater than those of other location in which significantly increased yields were obtained. However, it was generally the late postemergence treatments which had the reduced yields. Quackgrass was 20 to 30-cm tall and in the five- leaf stageeat the time of application which has been shown to be the critical stage of interference (5, 12%. Even though the duration of interference did not differ between here and other locations, the quackgrass at this location had obtained a larger size in a relatively short period of time. In addition, the postemergence grass herbicides are relatively slow acting which enables quackgrass interference following application. Therefore, it is critical to control the quackgrass prior to the five-leaf stage regardless of the duration of interference. In this case then, the early postemergence and split applications were more beneficial.’ 100 Table 20. Soybean yields in no-till soybeans with postemergence grass herbicides applied as early postemergence, late postemergence, and split applications. Kellogg Biological Station, Mi; 1983a. Soybean yield Treatmentb Rate EPC LPd Split ------------------ (kg/ha)------------------- Haloxyfop-methyl 0.28 1513 g-l 1123 b-j 1611 i-l Haloxyfop-methyl 0.56 1611 i-l 804 a-f 1513 g-l DPX-Y6202 0.28 1587 i-l 903 a-g 1342 e-l DPX-Y6202 0.56 1879 l 1074 b-i 1586 i-l Fluazifop-butyl 0.78 1562 h-l 927 a-h 1611 i-l Fluazifop-butyl 0.56 1562 h-l 708 a-d 1416 f—l Sethoxydim 0.56 757 a-e 391 a 732 a-e Sethoxydim 0.84 1220 b-k 659 a-c 1196 b-k No treatment - ------------ 635 a-b ------------ aMeans followed by a common letter are not significantly different at the 5% probability level according to Duncan's multiple range test. bAll treatments contained crop oil concentrate at 2.3 L/ha, with each application. CEP d Early postemergence application. LP Late postemergence application. 101 Quackgrass control evaluations the next spring, 46 weeks after application, showed very poor control with all selective herbicide treatments which indicates that the postemergence grass herbicides were ineffective in controlling quackgrass for more than a single season, whereas the non-selective glyphosate can control quackgrass for more than one season (Table 21). The final cultural system in which quackgrass control was examined was a continuous soybean, fall chisel plowed situation. Fall chisel plowing is less disruptive to soil, and therefore, quackgrass rhizoimes, than is moldboard plowing and is often referred to as conservation tillage. Quackgrass control evaluations showed no significant differences between time of application or between rates of haloxyfop-methyl and DPX-Y6202 (Table 22L However, late postemergence applications of ffluazifop-butyl were less effective than early postemergence applications and increased ratecihinot result hiincreased control. This indicates that fluazifop-butyl is less effective on the larger quackgrass than either haloxyfop-methyl or DPX-Y6202. fflflit applications of sethoxydim were more effective than either early postemergence or late postemergence applications. But by the late- season evaluation, control with all applications of sethoxydim are poor except for a split application of CL84 kg/ha. Quackgrass control data from fall chisel plowing were not unlike those from fall moldboard plowing where the single early postemergence application is as effective as the split application. This is because 102 Table 21. Subsequent season quackgrass control in no—till soybeans with postemergence grass herbicides applied as early postemergence, late postemergence and split applications. Station, Mi; 19833. Kellogg Biological Quackgrass control TreatmentC Rate EPd LPe Split (kg/ha) ------------ % --------------- Haloxyfop-methyl 0.28 37 b-g 23 a-e 33 a-g Haloxyfop-methyl 0.56 38 c-g 20 a-d 33 a-g DPX-Y6202 0.28 27 a-e 28 a-e 33 a—g 0PX-Y6202 0.56 37 b-g 30 a-f 40 c-g Fluazifop-butyl 0.28 28 a-e l7 a-c 33 a—g Fluazifop-butyl 0.56 38 c—g 13 a-b 37 b-g Sethoxydim 0.56 20 a-d 13 a-b 10 a Sethoxydim 0.84 27 a-e 13 a-b 17 a-c aMeans followed by a common letter are not significantly different at the 5% probability level according to Duncan's multiple range test. bQuackgrass control evaluated on 5/6/84, 46 weeks after early postemergence applications. CAll treatments contained cr0p oil concentrate at 2.3 L/ha, with each application. dEP Early postemergence application. eLP Late postemergence application. 103 .cowumuwpaqm mucmmcmswumoa mum; .cowumuPpaam mucmmcoemumog apgum adv emu .mcowumuwpaam oucmmgmsmpmoa apgmm Lmuum mxmmz NF .mm\m\opucomomm can; "meoquUv—aam mocmmLmEmumoa ngmm gmpcm mxmmz v .mm\m\m-=ommmmcpz "mew meowumzpu>m Fogucou mmmgmxuuaa mo mmumo a .ummu mace; mpapu—ae m.:mu==o op mcvvcouuo Fw>mp xpwpwnmnoga mm 6;» pm ucmgmwwmc zpucmuvwwcmwm was «go gmuump cossou a an cmzo—Po» cowgmq copuma—m>m co cpcpwz mcomzm 0-? NB e-a MN u-a mm e-P we F-u mm c-a mm em.o scquosumm - P-m oe a N - 8.“ me a a. om.o swuzxogpmm n-a me c-“ on a-a ON a-; we 8-“ mm a up ~¢.o swuxxoguwm 0-; mm 2-8 mm o-x as e-a mm .-o om L-e om om.o P»»=D-aocw-=_a - 2-8 mm o-a mm - n-u mm c-= mm ~¢.o Papan-aocwwaapa 0-; me. n-“ me =.0 em a-w on 5-9 me 2., we mN.o Fxozn-aocp~aspa o-a.~m o-s mm 0-x as m-c mm e-s om c-a mm mm.o No~o>-xao - o-n me 0-? we - c-s om L-x he N¢.o ~o~o>-xaa o-F we 0-? Nu 0.” mu m-c om c-o mm c-: Nm w~.o ~o~o>-xao 0 mm 0-5 mm o-m No a “a e-o mm L-s om em.o _»;pas-aoc»xo_a: - 0-5 mm 0-x NB - c-x Nu c-= Nm ~¢.o Panams-aoc»xopa= 0.” mu 0-; ch 0-? NB c-e om o-c no a-P me mN.o Facuos-aoc»xo_az ------------------------------&----------------------------- Aa;\mxv pram was we“ uw_mw was .ileam apex oucmspamc» .333 33 .8333; n—ogucou mmmgmxumzo .amme “P: .Lwrzou .mcovumuwpaam uppam new wucmmcmsmumoa mum— .mucmmgmemumoa ngmw mm cmVPQQm mmuwuragm; mmmgm wucomgmewpmoq gum: mammnxom Azora mewcu Ppmwv Ppmuucowam>gmmcou c? Pocucou mmmemxumao .NN «Pack 104 quackgrass shoots are at a uniform growth stage at the time of the early postemergence applications due to lack of soil disturbance in the spring. Although nonselective herbicides were not included in this location, the grower made spring applications of 1.68 kg/ha of glyphosate to quackgrass growing outside the experimental area and made an early-season cultivation. This resulted in near complete control of quackgrass season-long despite the fact the field was fall chisel plowed. Previously, effective quackgrass control was shown with glyphosate and SC-0224 applied in several spray volumes. At the conservation-till location, 0.56 kg/ha of fluazifop-butyl and sethoxydim were applied in four spray volumes. At the midseason evaluation, significantly higher quackgrass control was observed with fluazifop-butyl applied in 37, 65 and 131 L/ha than in 252 L/ha (Table 23). However, by late season this effect was no longer prevalent. Changing spray volumes did not influence control with sethoxydim. SUMMARY Cultural systems such as rotation and tillage practice can influence chemical control of quackgrass. Nonselective herbicides such as glyphosate and SC-0224 provided quackgrass control for more than one season when applied in the fall or spring. However, reduced control can result when herbicide coverage is reduced, as from tall wheat 105 .>\> &_ pm mpmgvcmucoo Pwo aoco zpwz ume5-xcmu mpszpwmcpu .cowmePFQQm mewm mxmmz m_ .mm\w\op -cOmmmm «pm; ”cowpmowfigam cmpwm mxmwz m .mm\w\m-:0mmmmuwz ”mew mcowumspw>w Focpcou mmmcmxumzc we mwpmon .pmmp mace; mPQPp—zs m.:mu::o op mcwvcouum Fm>wF zprwnmnoga &m esp pm pcmgwmmwc appcmowwwcmmm no: mew mepmp coesou m an umzoPPom vowgma :owpozrm>m cm cwgpvz mcmm2m w-m ow m-a mm 0.8 om e-a Am m-m me 5-3 me 2.8 co c-a mm om.o Ewasxogpmm 5.8 mm o-a om 0-; mo o-m No 2-8 om c-x Ne e-x NR L-P we om.o _sp=a-ro.Na=FL ---------------------&---------------------- Aa;\mxv m;\b New . .-rmr . H -mm_ lhm m;\4 New -FmP -mo -Nm apex upcmEpaaL» ,. ,.:ommwm mpmg comwmmwwz n_ocp:ou mmmcmxomso .mmwm— we: .Loézou .me:Fo> xmcam czom cw Umwpqam Ewuxxogpwm vac qusn-go+wNm=Fw saw: mcmwnxom Azora mewgo Fpmwv F—wg-cowpm>gmmcou cw Focpcou mmmcmxowzo .mm ergo» 106 stubble, or when applied in the spring following moldboard plowing since shoot emergence is not uniform. Late postemergence and split applications of postemergence grass herbicides more effectively controlled quackgrass in a spring moldboard plowed system than early postemergence applications. The spring disruption of rhizomes caused uneven shoot emergence such that shoots emerged after the early postemergence application. In no-till and fall-plowed systems, early postemergence applications were usually as effective as late and split applications. A cultivation substituted for the second half of a split application. Despite varying levels of season-long quackgrass control, significantly increased yields are obtained when quackgrass was treated prior to becoming 25 to 30-cm tall with five leaves. However, poor quackgrass control in late season may present harvesting difficulties. Effective quackgrass control with postemergence grass herbicides was usually limited to one season. 10. 11. 12. 13. LITERATURE CITED Baird, D. D. and G. F. Begeman. 1972. Postemergence character- ization of a new quackgrass herbicide. Proc. Northeast. Need Sci. Soc. 26:100~106. Behrens, R. and M. Elakkad. 1972. Quackgrass control with glypho- sate. Proc. North Central Weed Control Conf. 27:54. Behrens, R. and M. Elakkad. 1973. Quackgrass control with glypho- sate and atrazine. North Central Weed Control Conf. Res. Rep. 30:172—174. Brockman, F. E.. w. 8. Duke and J. F. Hunt. 1973. Agronomic factors influencing the effectiveness of glyphosate for quackgrass control. Proc. Northeast. Need Sci. Soc. 27:21-29. Dekker, J. 1981. Quackgrass control in soybeans with several postemergence applied herbicides. Proc. North Central Weed Control Conf. 36:110-111. Dekker. J. 1982. Translocation of several graminicides in quack- grass: I. Rhizome Node Viability. Proc. North Central Weed Control Conf. 37:47. Holm, L. G., D. L. Plucknett, J. V. Pancho and J. P. Herberger. 1977. The World's Worst Needs, Distribution and Biology. Univ. Press. Hawaii. 609 pp. Ivany, J. A. 1975. Effects of glyphosate application at differ- ent growth stages on quackgrass control. Can. J. Plant Sci. 55:8614863. Ivany, J. A, 1981. Quackgrass (A re ron repens) control with fall-applied glyphosate and other'EerElciaes. eed Sci. 29:382- 386- Kells. J. J., w, F. Meggitt and D. Penner. l98l. Factors influ- encing grass control with selective postemergence herbicides. Proc. North Central Weed Control Conf. 36:21—22. Linscott, D. L. 1970, The ten worst weeds of field crops. Quackgrass. Crops and Soils. 23:8-9. Sikkema. P. H. and J. H. Dekker. 1981. Determination of critcal quackgrass induced stress periods in soybeans. Proc. North Central Weed Control Conf. 36:24. Smith, Jr., L. L., H. Johnston, 8. C. Gerwick and E. A. Egli. 1982. Dowco 453-~a new postemergence herbicide for selective annual and perennial grass control. Abstr. Need Sci. Soc. Am. p.107. 107 108 Sprankle, P. and w. F. Meggitt. 1972. Effective control of quackgrass with fall and spring applications of glyphosate. Proc. North Central Weed Control Conf. 27:54. Sprankle, P., w.F. Meggitt and R. C. Bond. 1973. Quackgrass control with glyphosate in agronomic crops. North Central Weed Control Conf. Res. Rep. 30:157-159. Waldecker, M. A. and D. L. Wyse. 1984. Quackgrass (A ro ron ‘Arepens) control in soybeans (81 cine max) with BAS 905g 0H. KK-80, and R0-13-8895. Weed Sci. 32:%7~75 CHAPTER 4 POTENTIAL REDUCTION IN QUACKGRASS (Agrogxron repens (L.) Beauv.) CONTROL FROM ADDITIONS 0F. BROADLEAF HERBICIDES TO GRASS HERBICIDE APPLICATIONS ABSTRACT Postemergence tank-mix applications of two broadleaf and four grass herbicides were made to three- to five-leaved quackgrass to examine for antagonism in the form of significantly reduced control compared to that of grass herbicides only. .Antagonism varied with location and herbicide. Addition of acifluorfen (sodium 5-(2-chloro-4 (trifluoro-methyl)phenoxy)-2-nitrobenzoate) to applications of haloxy- fop-methyl (methyl 2-(4-((3-chloro-5-(trifluoromethyl)-2—pyridinyl)- oxy) propanoateL, DPX-Y6202 (2-(4-((6-chloro-2-quinoxalinyl)oxy)- phenoxy)propionic acid, ethyl ester) and fluazifop-butyl ((_+_)-butyl-2- (4-((5-trifluoromethyl)-2-pyridinyl)oxy)phenoxy)propanoa,te) resulted in reduced quackgrass control 15 weeks after application, but not 4 weeks after. Both acifluorfen and bentazon (3-siopropyl-1H72,l,3,- benzothiadiazin 4(3H)-one 2,2,-dioxide) reduced control with sethoxydim (2-(1-(ethoxyimino)-butyl)-5-(2-(ethylthio)propyl) 3-hydroxy-2-cyclo- hexen—l-one) 4 and 15 weeks after application. Increased rates of 109 110 haloxyfop-methyl, DPX-Y6202 and fluazifop-butyl often circumvented antagonism. An application of either acifluorfen or bentazon followed the next day by haloxyfop-methyl resulted in antagonism 15 weeks later whereas the reverse did not. Antagonism manifested in late season but not early after application suggests that acifluorfen and bentazon do not interfere with the initial phytotoxic effects of the grass herbicides, but may reduce translocation of the grass herbicide to quackgrass rhizomes thereby'enabling increased generationcfiishoots fron1the rhizomes. -Antagonisnidid not significantly affect soybean (Glycine max L.) yields. INTRODUCTION Quackgrass is a rhizomatous perennial grass that has been referred to as one of the world's worst weeds and is a serious weed problem in soybeans (Glycine max U“) Merr.)irithe Northern temperate areas of the United States (1, 7, 9). The recent development of selective postemergence applied grass herbicides has given soybean growers a new option for quackgrass control. Consequently, a grower may wish to tankmix a broadleaf herbicide with a grass herbicide to increase the spectrum of a postemergence application. However, this may result in antagonism in the form of reduced quackgrass control. Reduced control of various annual grasses has been observed from additions of acifluorfen UL42-chloro-4-(trifluoromethyl)phenoxy)-2-nitrobenzoic acid) and bentazon (3-isopropyl-lfl-2,l,3-benzothiadiazin-4(3H)-one-2,2- dioxide) to applications of sethoxydim (2-(1-(ethoxyimino)-buty1)-5-(2- ethylthio-propyl)-3-hydroxy 2-cyclohexene-l-one), haloxyfop-methyl (methyl—2-(4-((3-chloro-5-(trifluoromethyl)-2-pyridinyl)oxy)phenoxy) propanoate), DPX-Y6202 (2-(4-((6-chloro-2-quinoxalinyl)oxy)-phenoxy)- propionic aicd, ethyl ester), and fluazifop-butyl ((1)-butyl-2-(4((5- (triluomethyl)-2-pyridinyl)-oxy)phenoxy)propanoate) (4, 5, 6, 10, 13). In some cases, antagonism in annual grasses was overcome by increasing the herbicide rate, separating the application of the tank-mix 111 112 components, or by making application before the grass became too large (2. 3, 6,10,11). Angatonisnlrnay also be a factor in quackgrass control. Kells et al. (8) obtained reduced quackgrass control from additions of acifluorfen and bentazon to applications of fluazifop-butyl, haloxyfop- mehyl and sethoxydim. This antagonism presents a potential problem with postemergence applied herbicides for broad-spectrum weed control. The objectives of this research were to (l) examine the potential antagonism in quackgrass from tank-mix applications of the postemergence broadleaf herbicide acifluorfen and bentazon with several rates of postemergence grass herbicides haloxyfop-methyl, DPX-Y6202, fluazifop-butyl and sethoxydim; (2) examine the effects of separation of application of broadleaf and grass herbicides on antagonism, and (3) determine the effects of antagonism on soybean yields. MATERIALS AND METHODS Field experiments were conducted at three locations in areas of dense quackgrass infestations. All herbicide applications were made with a compressed air tractor sprayer using flat fan nozzles at a spray volume of 262 L/ha at 324 kPa. The experimental design was a randomized complete block. Visual evaluations of quackgrass control were made at several times following herbicide application. Evaluations were based on a 0 to 10 scale where 0 indicated no quackgrass control and 10 indicated complete control. Untreated plots 113 were used as the basis for no control. Control data were converted to decimal form, subjected to the arcsin data transformation and then analyzed for mean separation using Duncan's miltiple range test. Quackgrass control data presented here are non-transformed and have been converted to percent. Soybean yields were taken at two locations using a small plot combine. The first experiment was established on the Michigan State University Agricultural Experiment Station onziCapac loam in 1982. The field was moldboard plowed, disked and field cultivated on June 7 and planted to 'Evans' soybeans with 24-cm row spacing on June 8. Postemergence applications of herbicides were made on June 25 when the quackgrass was 10 to l8-cm tall with three to four leaves and soybeans were in the unifoliolate leaf stage (VlL- Crop oil concentrate was applied at 2.3 L/ha with all treatments except those containing acifluorfen. In this experiment, the commercially formulated acifluorfen contained surfactant. This formulation was discontinued following 1982. Plot size was six rows by 10.7in, and there were four replications. Control evaluations were made 4 and 15 weeks after herbicide applications. The four middle rows of each plot were harvested for yield on November 14. In 1983, an experiment was established in Clinton County near Fowler, Michigan on a Metamora-Capac sandy loam. The field was chisel plowed in the fall of 1982. Ilpreplant incorporated application of trifluralin (a,a,a-trif1uoro-2,6-'dinitro-N-N-dipropyl-p-toluidine) pl u s metr i buz i n (4-amino-6-tert-butyl-3-(methylthio)-_a_s_-tri azin-5(4H)- 114 one) at 0.84 and 0.28 kg/ha, respectively, was made on June 15 for the control of annual weeds. The field was planted to 'Hardins' soybeans with 76-cm row spacing on June 17. Plot size was four rows by 12.2 m with three replications. Postemergence applications of herbicides were made on July 7 when the quackgrass was 10 to 15-cm tall with three to four leaves and the soybeans were in the unifoliolate to second trifoliolate leaf stage (V1 to V3). Crop oil concentrate was applied at ZJBL/ha with all treatments except those containing acifluorfen where lJZL/ha was used. Visual ratings were taken 5 and 13 weeks after application. An experiment was established in 1983 in Kalamazoo County at the Kellogg Biological Station near Hickory Corners, Michigan on a Kalamazoo loam. The field was planted to soybeans in 1982 and was not tilled following harvest. An application of paraquat at(L56 kg/ha was made on May 25. The field was planted to 'Corsoy' soybeans with 76-cm row spacing on June 2. Plot size was four rows by 12.2 m with three replications. A preemergence application of metolachlor (2-chloro-N— (2-ethyl-6-methylphenyl)-N_-(2-methoxy-l-methylethyl) acetamide) plus metribuzin at 2.24 and 0.42 kg/ha respectively, was made on June 2 to control annual weeds. Early postemergence applications of herbicides were made on June 22 when the quackgrass was 15 to 20 cm tall with three to four leaves and the soybeans were in the first trifoliolate (V2). Late postemergence applications were made on July'6 when the quackgrass was 20 to 30.5-cm tall with five leaves and the soybeans were in the fourth trifoliolate leaf stage (V5). Aseries 115 of teatments involving a one-day separation of applications of haloxyfop-methyl and either acifluorfen or bentazon was initiated where the first application was made on June 22 and the second on June 23. Crop oil concentrate was applied at 2.3 L/ha with all treatments except those containing acifluorfen where 1.2 L/ha.\vas used. Control evaluations were made 5 and 15 weeks after herbicide applications. The two center rows of each plot were harvested for yield on October 18. RESULTS AND DISCUSSION Antagonism was considered to have occurred if the resultant quackgrass control from a tank-mix application was significantly less than that obtained with in grass herbicide applied alone. Data indicated that the antagonism level varied with herbicide and location. At the East Lansing location, there was no antagonism observed four weeks after application with any tankmix applications containing haloxyfop-methyl, DPX-Y6202 or fluazifop-butyl (Table 1L. However, fifteen weeks after application antagonism was observed in plots treated with each of these three herbicides plus acifluorfen, but not bentazon. Tank-mix applications-of acifluorfen plus sethoxydim re- sulted in antagonism expressed at both the early and later evaluations, whereas antagonism with bentazon plus sethoxydim was observed only at the later evaluation. Soybean yields from treatments which resulted in antagonism were not significantly different from those which did 116 .»Pm>wpomammc .m;\4 m.m vcm m;\mx vw.o pm mpmgwcwucoo Fvo aoco warm CONmpcwn spwz vmxwe-xcmp pamanmgpm .>_m>wpomammc .m;\4 N._ use m;\mx om.o pm mgmcucmocou Fwo aogo sza cmeospwwuw saw: umwa-xcmp ucmspmmghu .m;\4 m.N um mpmcpcmocou Pwo aoco spwz vmwa-xcwu acoEpmmcpo .eowpaowzaaa emote mxaaz mp .mm\_z\o_ -commmm mum; ”coprUWPaam cmpwm mxmmz q .Nm\m~\n-commmmvwz ”mcm mcovpmsFm>m Pocpcou mmmcmxowzc mo mmpmon .ummu mace; mPprP:E m.cmoczo op mcvvcwoom Fm>mp prFwnmnocg gm mcp gm pcmcmmwwv >chmuwmwcmwm poc mew mepmp 205200 a xn umzoF—om cowgma cowpm:_w>m cm cwcuwz mcmmzm n-a em a me m-8 _A u-n _8 a om m-a me mm.o Ewesxagymm m-e mu 0.3 _o :-n m“ m-w 0N L-8 F“ m-a ax om.o _»p=n-a0LwNa3_L c-u w“ v.8 we h-L em g-L mm m-a on g-L em om.o Nomo>-xao x-; mm v.6 we h-L am g-L mm m-e me L-m mm om.o _s;pae-aocsxora: -----------------&------- --------- ---- Aa;\mxv 2mm Hu< goo mzmm eHoq uuoo apex “caspaaec :ommmm mum; cemmmmumz QFOchou mmmgmxomzo .mmmmP we: .mcwmcmb pmmm .CONmpcmn co :wwcozrdwum cpwz xwe-xcmp :? co mcoFm umwpaam mvvuwncm; mmmcm mucmmeEmpmoa saw; mcmmnxom cw Pocucoo mmmcmxomzo ._ manF 117 not, and all treatments resulted in soybean yields significantly higher than no treatment (Table 2). At the Fowler location, two rates of each of the postemergence grass herbicides were applied alone and in tank-mix with acifluorfen and bentazon. -At this location, quackgrass control with sethoxydim plus crop oil concentrate was poor at both rates and any potential antagonism was therefore, inconsequential (Table 3). A tankmix application of’ CL28 kg/ha of fluazifop-butyl plus acifluorfen was the only treatment to result in antagonism 5 weeks after application. By increasing the rate of fluazifop-butyl'UD(LS6 kg/ha, antagonism due to addition of acifluorfen was avoided. Thirteen weeks after application, quackgrass control from 0.28 kg/ha of fluazifop-butyl plus crop oil concentrate had decreased considerably and consequently, there was no significant effect due to tankmix. Tankmix applications of (L28 kg/ha of haloxyfop-methyl with acifluorfen and bentazon resulted in antagonism 13 weeks after application as did an application of DPX- Y6202 at 0.28 kg/ha plus acifluorfen. However, antagonism was avoided in both cases by increasing the rate of the grass herbicide in the tankmix to 0.56 kg/ha. At the Kellogg Biological Station location, early postemergence tank-mix and same day, separated applications of haloxyfop-methyl and acifluorfen did not result in antagonism (Table 4). Similarly, addition of acifluorfen and bentazon to either the early postemergence or late postemergence applications of a split application of haloxyfop- methyl did not result in antagonism (Table 5). An application of 118 Table 2. Soybean yield in soybeans treated with postemergence grass herbicides applied alone or in tank-mix with acifluorfen or bentazon. East Lansing, Mi; 1982a. Sgybeangyield Treatment Rate cocb AC1C BENd (kg/ha) -------------- % ------------------- Haloxyfop-methyl 0.56 2455 b-c 3212 c 2257 b-c DPX-Y6202 0.56 2705 b-c 2568 b-c 2905 b-c Fluazifop-butyl 0.56 2426 b-c 2779 b-c 2249 b-c Seethoxydim 0.56 2793 b-c 2860 b-c 2555 b-c No treatment - -------------- 774 a---------------- aMeans followed by a common letter are not significantly different at the 5% probability level according to Duncan's multiple range test. bTreatment tank-mixed with crop oil concentrate at 2.3 L/ha. CTreatment tank-mixed with acifluorfen plus crop oil concentrate at 0.56 kg/ha and 1.2 L/ha, respectively. dTreatment tank-mixed with bentazon plus crop oil concentrate at 0.84 kg/ha and 2.3 L/ha, respectively. 119 .OFO>ONOOOOON .O;\O O.N cam OONOO OO.O NO ONOLNOOOOOO FOO Oogu OOPO OONOOOOO cpwz OmeE-xcmu pcprOOLNO .OFO>ONOOOOOL .O:\O m._ OOO OONOX OO.O NO mchpcmucou FOO Oogo OOFO cmmgozpmwum gpwz uwaE-xcmp pcmEpOONHO .O;\O O.N ONONOOOOOOO FOO OONO saw: waOE-xcmp acmEpOmLNO .coOpOuOFOOO LONOO xmmz OP .mm\m\o_ -coOOOO ONOO OOO :oOpOOOPOOO Nmpmm Oxmwz m .Om\w\w-OOOOOOOO2 ”ONO OOOOHOOFO>O Pogpcoo OOOmeOOOc No Ompmon .pmmp OOOOL OFOONPOE O_:Ooczo op mcwncouum Fm>m_ ONOPOOOOONO Om asp pm pcmgmwwwu OPHOOONOOOOOO poc ONO Nmuump coEEou O On OOZOFFOO OOONOO :oNpO:_O>m :O cwgpwz Ocmsz O-O OF O-O.ON, O-O ON , U-O.OO_ O-O OO O-O OO IOO.O EOOOOOOOOO O-O ON O N O N. _ O-O OO O-O NO O N_ OO.O EOOOXOOOOO O-O NO O-O NO O-O NN O-O NO o-O ON O-E OO OO.O ._OOOO-OOOONOOFO e-O OO O-O NO O-O NO O-O NO x-u OO L-N ON ON.O _OOOO-OOOONOONO O-O OO O-O NO O-x NN O-O NO O-O ON L-O OO O0.0 NONO>-XOO o-O OO O-O OO o-O ON O-O NN o-O OO O-O NO ON.O NONOO-XOO O-O NO F-O OO O-O NO O-O ON L-_ ON O-5 OO OO.O POOOOs-OOONXONOI O-O NO O-O OO o-N NN s-O OO e-O OO O-O ON ON.O _O;OOe-OOOOXO_OO ----- ------ ---------O- -------- --------- ----- -- NOONOOO .ZOO‘,. ..HOO OOO. ..LOZOOH . -OOO< UOOO OOOO OOOEOOOLN coOOmO mum; cowmmmwwz . OFOONOOOOOONOOOOOO .Omwmp ”Oz .NOFZQO .OONONOOO OOO CONNOOPOOOO zuwz xwe-chp cw No OOOFO OOOFOOO OOOOONOLOO OOOcm mocmmcmempmoa saw: OOOOOOOO cw Pogucou OOOmeUOOo .m OFOON 120 OOOOOOOOONOOO Oucmmgmsmumoa NONOO Oxmmz m .mm\m~\N-OOOOOOOO2 .wuogucoocou POO coco u uoou .OcoOuOuOPOOO wucmmgmsmumoa cmuwm Oxooz mp .OONNNON-OOOOOO can; "mum OOOONOONO>O Fogucou OOONOxuOOu we Owumo a .ummu mono; «NOONFOE O.:Ou:=o o» mcwucouum Nm>m— OuONOOOOOLO mm Ogu NO NOOOOOONO ONNOOOONNOOOO yo: ONO gmuuwp cossou O OO umzoppow OOONOO :oOuOO~O>m :O OOOOO: Ocomzn O-O OOO ucosuawgu oz N-O OONN O-5 OO N OO_ OONO N._ + O0.0 OOO + OONOOOOO OONO N._ + OO.O NOOO + NNOOOe-OOONXONOO P-O NONF O-O NO _-O NO OONO N._ + O0.0 OOO + OONOOOOO OONO N.N + ON.O OOOO + NOOOOs-OOOOXONOO N-O NNON o-x ON . N-O NO OONO O.N + O0.0 OOO + OOOOOONOOOO OONO N.. + OO.O OOOO + _OOOOs-OOOOxONOO N-O OOON e-O NO x-O NO OONO N.N + O0.0 OOO + OOOOOONOFOO OONO N._ + ON.O NOOO + NOOOOs-OOOOxONO: Out OEOO .cowumuppnna «pagomum O-O ONNN O-O ON F-O NO OONO O.N + OO.O + OO.O OOO + OONOOOOO + PNOOOe-OOOOXONO: N-O ONON O-O ON x-O OO OONO O.N + OO.O + ON.O OOO + OONOOOOO + NOOOOs-OOONXOOOO F-O OFON O-O ON _-O NO OONO N.N + OO.O + OO.O OOO + OOOLOONOOOO + NOOOOe-OOOOxONOO N-O OPON O-O ON O-O NO OONO N.P + O0.0 + ON.O OOO + OOOLOOPONOO + NOOOOe-OOOOXONOO copuouppaqa xOs-xcop N-O ONOF o-O ON 3.? OO OONO O.N + O0.0 OOO + .NOOOe-OOOOXONOO P-O OOO_ O-O ON O-O OO OONO O.N + ON.O uOOO + _O;OOs-OOOOxONO= NOONOOO ------O------ NOONOOO upmw> coOOmO mum; :oOOmOOOE- muam ucwEuOmNh OOOOOOO Nogpcou OOONOOOOOO a .OmwON up: .OOOpOpm NOOOOOFOOO Omoppmx .OOOOuOOOPOOO «HONOOOO No xOE-xcmu :_ OOONOOO OONONOOO wen Oomgozpwwum OONO pxgme-Oomzxopmz sup: mcmmnaom c? Pogucou Omagmxumao .e upon» 121 .OONO N.N uO muOgucmucou POO OONO OOOOOOOOO OOOOOOFOOOO OONO ngums-OomxxopO; yo OOOOEOOONO "OONO O.N NO muOgucmucou FOO Oogu OOOOOucou OONOOOOO OOFO POOOOE-OowaxopOz OOO Nxsums-OOOOxOPO; mo mucmsuOoghu .OOOOOOONOOO oucmmgmsmumoa ONOOO Nmqu Oxmm: mp .mm\~\op-:OOOOO «HO; “comuOuO—OOO mucmmgmsmumoa OFLOO NOOOO Oxmmz m .OONONNN-OOOOOOOOZ "OLO OOOONOONO>O pogucou OOOgmxanc we mmuOoa .umma mchc O—OOOFOE O.cOu::o O» OOOONOOOO pm>w~ OOONOOOOONO 3 23 «O acmgmtvv OSOOONNESO no... ONO .832 5.5.8 O .3 83:8 “.2ng :oSOEON’O :O 5.5:, .385 Tana mmm - - OOOEOOOLO oz N-O OOOP O-N OO , F OON OO.O + OO.O "ON.O OONOOOOO + FNOOOs-OOONxONO; O_OOOOE-OOOOxO_O= _-O FPON o-O NN N OO_ ON.O “OO.O + ON.O NNOOOO-OOOOXOFOO mOONSOOO + POOOOE-OOOOOO_OO P-O OFON O-O ON _-O OO OO.O "OO.O + O0.0 POOOOe-OOOOXONOO mOONSOOO + _OOOOs-OOOOxO_OO F-O NOON O-5 OO P-x OO OO.O + ON.O mON.O OOOLOONONOO + FNOOOe-OOOOxONOO "NOOOOs-OOOOXONOO P-O OOOF O-5 OO .-O NO OO.O + O0.0 OO_.O OOOLOONOOOO + POOOOe-OOONOOPOO N_OOOOe-OOOOXOPO= N-x OOOP O-O ON F OON ON.O "OOHO + ON.O NOOOOE-OOONOO_O= NOOOLOONOOOO + NNgume-OOOOxOFOO P-O NOON O-O OO x-O OO OO.O mOO.O + ON.O NOOOOe-OOOOXONOO OOOOOOONOOOO + ONOOOe-OOOOxONOO P-O OPON c-O OO N OOF ON.O uON.O NOOOOs-OOONXO_O; N_OOOOe-OOOOXOPOO F-O _POP N-O OO x-O OO ON.O “ON.O _OOOOs-OOOOXONO= M.OOOOs-OOOOXOFO= NOONOOO -----N------ NOONOOO OFON> :oOOmO OuOO :oOOmOnOz .oan . oucmEpOogp cOOOOom Nogucou OOOmequo. O .OOOON “Oz .OONOOOm NOONOOFOOO mooppmx .OONOOOOO OOO OOONOONOOOO Oz—O stume-OOOOxOFO; we OOOOOOOOPOOO ONFOO OON3 OOOOOOOO ON Nogucou OOONOxuOOo .m ONOON 122 haloxyfop-methyl followed the next day by an application of either acifluorfen or bentazon also did not result in antagonism (Table 6). However, an application of either acifluorfen or bentazon followed the next day by an application of haloxyfop-methyl resulted in antagonism expessed fifteen weeks after application. However, this antagonism did not significantly affect yields. SUMMARY Antagonism varied with location and herbicide. Variations may be due to differential response to herbicides by the different quackgrass biotypes. Quackgrass biotypes have been shown to respond differently to glyphosate (12). There was generally no antagonism observed at the early control evaluations. In most instances where antagonism occurred, it was not expressed until the later rating period in the form of increased shoot regrowth. This would suggest that the broadleaf herbicides are not interferring with initial action of the grass herbicides because phytotoxicity is observed at the midseason evaluation. Increased regrowth observed later in the season with tank-mix applications suggests reduced translocation of the grass herbicide from the treated foliage to the rhizomes. A reduction in grass herbicide concentration in the rhizomes would enable increased generation of shoots from rhizomes. The broadleaf herbicides acifluorfen and bentazon, while not phytotoxic to quackgrass, could predispose the quackgrass for reduced translocation. Evidence for this .OONO N._ HO prgpcwucoo FOO Oogo OOOOOOOOO :meOONwNOO No OOOOEOOOOO OOONO O.N pO OOOLOOOOOOO POO OONO Owchucou OONOOOOO OcO Panama-OowaOPO; mo OOOOEOOOLOO .OOOOOOONOOO OOOOONOEOOOOO LOOOO Oxmmz OP .OONN.o_-OOOOOO ONO; mcoOuOOOPOOO OOOOONOEOOOOO OOONO Oxmwz m .OONONNN-coOOmOOOz "OOO OcoOpOOFO>w Fogpcou OOOmeuOOO mo OOOOOO .ummp OOOOO ONOOu—Os O.:Ou:Oo Op mcwugoqu FO>OF OOONOOOOOLO NO mg» HO OOOLOOOOO OFOOOOOOOOOOO poc OLO Omupmp cossoo O OO OmzoFrow OOONOO :oNpOOPO>m :O OOOOOZ OcOOzO 123 aim mmm .- n n “cwEummLp oz _-O OOON O-O NO O-O OO OO.O ”OO.O Pngme-OOONXOFOO m OONOOOOO _-O OOOF O-O NO O-O NO ON.O mOO.O NOOOOs-OOOOXOPOO m OONOOOOO _-O ONO_ O-O OO O-O OO O0.0 mOO.O FOOOOE-OOOOXOPOO m OOOLOO_OOO< _-O OOOF O-O OO O-O OO ON.O mOO.O _OOOO5-OOONXONOO m OOOLOO_OOO< N-O OOOF O-O NN F-O NO O0.0 mOO.O OONOOOOO m FOOOOe-OOOOXONOI _-O NOOO e-O NO O-O OO OO.O mON.O OONOOOOO m _OOOOe-OOOOXOFOI _ OOO_ O-s OO N OON O0.0 mOO.O OOOOOO_OOOO m _OOOOE-OOONXOPOI _-O OOOF O-O ON O-; OO OO.O ”ON.O OOOOOOOOOOO m FNOOOs-OOONXO_OI N-O ONO? O-O ON O-O OO - mOO.O - m FOgume-OOONXOOOI _-O OOOF 0.; ON O-O OO - mON.O - m _OOOOE-OOOOXOFOI . OOO Ocoomm m OOO OONOO NOONOOV - ----- ---O- ----- --- NOONOOO OFOO> :oOOmO OOOO._coOOmOOOz _ mpOm OOOOEOOONO saga Ezce...§.§» . . ._ .NOmwOF.mO: .OOOOOOW FOoOmo—owm moorpmx .OcoOuOoOFOOO $0 :oOpOOOOOO OOO-mco O saw: OONOOOOO OOO :meOOPwOoO OOFO POOOOEIOOOOXOPO; sng OOOOOOOO cw Pogpcou OOOmequo .O OFOOO 124 was observed at the Kellogg Biological Station where the broadleaf herbicides applied a day before the grass herbicides resulted in antagonism whereas the reverse did not. Antagonism did not reduce yields since it was not manifested until late in the season which is well after the early growth stages of soybeans which are the most susceptible ix) weed interference. Although antagonisni did not adversely affect yields, higher quackgrass populations may occur the following spring hiareas where antagonism had previously occurred. Further research is needed to investigate the physiological processes affected which result in antagonism. 125 LITERATURE CITED Anonymous. 1970. Selected weeds of the United States. Agric. Handbk. 366. U.S. Dep. of Agric./Agric. Res. Serv. 436 pp. Campbell, J. R. and D. Penner. 1980. Factors affecting the activity of bentazon with diclofop and BAS 9052. Abstr. Need Sci. Soc.lmn p. 13. Chow, P.N.Fh 1983. Herbicide mixtures containing BAS 9052 for weed control in flax (Linum usitatissimum). Need Sci. 31:20-22. Campbell, J. R. and D. Penner. 1982. Compatibility of diclofop and BASF 9052 with bentazon. Need Sci. 30:358-362. Dexter,l& G” J.[L Nalewaja.and S.[L Miller. 1984. Antagonism between broadleaf and grass control herbicides. Abstr. Need Sci. Soc. Am. p. 5-6. Dortenzio, w. A., J. T. Daniel, S. A. Harrison, H. K. Majjure, S. H. Newell and R. P. Rose. 1984. The effectiveness of fluazifop-butyl alone and in tank-mixture with bentazon or acifluorfen. Abstr. Need Sci. Soc. Am. p. 6-7. Holm, L. G., D. L. Plucknett, J. V. Pancho and J. P. Herberger. 1977. The World's Worst Weeds, Distribution and Biology. Univ. Press. Hawaii. 609 pp. Kells, J. J., H. F. Meggitt and D. Penner. 1981. Factors influencing grass control with selective postemergence herbicides. Proc. North Central Weed Control Conf. 36:21-22. Linscott, D. L. 1970. The ten worst weeds of field crops. Quackgrass. Crops and Soils. 23:8-9. Renner, K./L and R.(L.Harvey. 1983. Postemergence control of giant foxtail (Setaria faberii Herm.) and wild proso millet (Panicum milaceum L.) in soybeans. Abstr. Need Sci. Am. p. 7-8. Ritter, R. L. and T. C. Harris. 1981. Interactions of postemergence soybean herbicides. Proc. Northeast. Need Sci. Soc. 35:63. 12. 13. 126 Westra, P. and D. L. Wyse. 1978. Control of quackgrass biotypes with glyphosate. Proc. North Central Weed Control Conf. 33:106. Williams, C. S. and L. M. Wax. 1984. and haloxyfop-methyl or sethoxydim. 6. The interaction of bentazon Abstr. Need Sci. Soc. Am. p. CHAPTER 5 EFFECT OF ACIFLUORFEN AND BENTAZON ON ABSORPTION AND TRANSLOCATION OF HALOXYFOP-METHYL AND DPX-Y6202 IN QUACKGRASS (Agropyron repens (L.) Beauv.) ABSTRACT Translocation of 14C-haloxyfop-methyl (methyl 2-(4-((3-chloro-5- (trifluoromethyl)-2-pyridinyl)oxy)phenoxy)propanoate) in quackgrass (Agropyron repens (L.) Beauv.) out of the treated area (the middle 2.5- cm of the second of three leaves) was significantly reduced in plants in which 0.56 kg/ha of acifluorfen (5-(2-chloro-4-(trif1uoromethyl) phenoxy)-Z-nitrobenzoic acid) and 0.84 kg/ha of bentazon (3-isopropy- lfl—2,l,3-benzothiadiazin-4(3H)-one 2,2-dioxide) were added in tankmix to a.CL07 kg/ha application of haloxyfop-methyl. Translocation of 14C was also reduced to the lower leaves. This reduction was not seen at higher rates of applied haloxyfop-methyl. Bentazon reduced quackgrass absorption of 14’C-DPX-Y6202 (2-(4-((6-chloro-2-qunioxalinyl)oxy)- phenoxy)-propionic acid, ethyl ester) while acifluorfen reduced translocation to lflua tip of the treated leaf. Absorption and translocation of 14C-haloxyfop-methyl and 14C-DPX-Y6202 in quackgrass was not affected by a 24 h pretreatment with acifluorfen and bentazon. Considerably more 14C-haloxyfop-methyl than 14C-DPX-Y6202 was absorbed 127 128 by quackgrass, although amounts translocated to rhizomes and small shoots were comparable. INTRODUCTION Attempts for broad spectrum weed control with postemergence applications of tankmixes of broadleaf and grass herbicides may result in control levels that are lower than expected due to herbicide interaction (4). Woldentatios and Harvey (7) found that tank-mix applications of diclofop-methyl (2,(4-(2,4-dichlorophenoxy)phenoxy) propanoic acid) and bentazon (3-isopropyl-lH¢2,l,3-benzothiadiazin- 4(3H)-one-2,2-dioxide) reduced uptake of 14C-diclofop by giant f6xtail (Setaria faberi Herrm.) leaves. Similarly, Williams and Wax (6) found reduced penetration of 14C-haloxyfop-methyl (methyl 2-(4-((3-chloro-5- (trifluoromethyl)-2-pyridinyl)oxy)phenoxy)propanoate) and MCI-fluazi- fOp-butyl “fig-butyl -2-(4-((5-(trif1uoromethyl) -2-pyridinyl) oxy) phenoxy)propanoatefl penetrated into German millet (Setaria italica (LJ Beaqu leaves when applied in a mixture containing bentazon. Rhodes and Coble (5) found that bentazon reduced absorption but not translocation of 14C-sethoxydim (2-(l-Uathoxyimino)butyl)-5-(2- (ethylthio) propyl)-3-hydroxy-2-cyclohexene-l-one) irI goosegrass (Eleusine indica U“) Gaertn.L Quackgrass (Agropyron repens (L.) Beauv.) is a rhizomatous, perennial weed of world—wide significance (1%, Kells et. al.(2, 3) found that tank-mix applications containing either bentazon or acifluorfen UL42-chloro-4-(trifluoromethyl)phenoxy) -2-nitrobenzoic 129 acid) with 0.56 kg/ha applications of fluazifop-butyl, sethoxydim or DPX-Y6202 (2-(4-((6-chloro-2-quinoxalinyl)oxy)-phenoxy)-propionic acid, ethyl ester) resulted in significantly reduced quackgrass control compared to that of the grass herbicides applied alone. However, acifluorfen and bentazon did not affect absorption and translocation of 14C-fluazifop-butyl in quackgrass (2). In field trials by the author, the addition of acifluorfen and bentazon to applications of several grass herbicides did not cause reductions in quackgrass control 4 weeks after treatment. lhnwever, significantly increased quackgrass regrowth occurred'KBto 15 weeks after application hiplots treated with tank-mix applications which suggests that acifluorfen and bentazon may be reducing translocation of the grass herbicide throughout the quackgrass plant including rhizomes which would enable regrowth. Therefore, the objectives of this research were to examine absorption and translocation of 14C-haloxyfop-methyl and 14-C-DPX-Y6202 in quackgrass plants treated with several rates of the respective grass herbicide both alone and in tankmix with acifluorfen and bentazon. In addition, the effects of a 24 h quackgrass pretreatment with acifluorfen and bentazon on absorption and translocation of these two grass herbicides were examined. MATERIALS AND METHODS General Procedures. Six to eight node quackgrass rhizome sections were planted in 473 ml plastic containers filled with number 2 grade vermiculite and soaked with tap water after which they were watered on alternate days with 50 ml of Hoaglandhs solution. The containers were placed in a glasshouse with full sunlight supplemented by sodium halide lights with an intensity of 280 uE/mZ/s with a l6 h photoperiod. Temperature was 27 i 3°C. After shoot emergence, rhizomes were trimmed to four-node sections in which two adjacent shoots were on the end two nodes and the other two nodes lacked shoots. When shoots had reached the three-leaf stage, the shoot next to the end was cut with a razor blade to 2-cm from the rhizome. Preliminary tests showed complete shoot regrowth following cutting with no adverse effects. Treatments were initiated approximately 5 h following cutting. The cutting operation was performed so as to simulate a shoot which had not yet emerged and was dependent on the larger shoot for translocation of assimilates. Treatments of non-14C labelled herbicides were applied in a spray chamber with a stationary nozzle with plants on a moving belt. Spray volume was 355 L/ha at a pressure of 220 kPa. The vermiculite was covered with a paper towel during application to prevent root uptake of the herbicide. 130 131 Effect of Tankmix and Rate. A factorial arrangement of treatments was applied where plants were treated with three rates of either haloxyfop-methyl or DPX-Y6202 alone or in tankmix with 0.56 kg/ha of acifluorfen or 0.84 kg/ha of bentazon. Grass herbicide rates were selected so as to have a normal field-use rate ULZB kg/ha), a low rate (l/4x or 0.07 kg/ha) and a high rate (4x or 1.12 kg/ha). Broadleaf herbicide rates are the labeled rates for field use. Crop oil concentrate was applied with each treatment.at 2&3L/ha.except those containing acifluorfen where 1.2 L/ha was used. The middle leaf of the three-leaved quackgrass was supported on an inverted 946-ml, l4-cm tall plastic cup to insure full coverage of the adaxial surface. Immediately following passage under the spray nozzle, the center 235 cm of the middle leaf was treated with a 2 pl solution containing either 0.2 uCi of 14C-haloxyfop-methyl (phenyl ring label, 11.2 mCi/mM) or 14C-DPX-Y6202 (phenyl ring label, 1047 mCi/mM). Applications were made with 5 pl syringe. Treatment solution of 14C was allowed to mix witWithe sprayed herbicide solutionOF Om Os“ OO OOOLOLOOO OPOCOOOOOOOOO poc wLO HLOO pcOFO O OOOOO3 OcOsz O 0.0 O O.O O O._ O-O O._N O-O O._O O _.N_ O0.0 + NN.N OONOOOOO + _OOOOe-OOOOXOPOO O 0.0 O O.O O _._ O-O O.ON O-O O.OO O 0.00 O0.0 + N_._ OOOOOO_OOOO + _OOOOe-OOOOXOOOI O O.N O _._ O-O O._ O-O N.ON O N.OO O 0.0_ NO.O _NOOOE-OOOOXONO= O N.O O O.O O O._ O-O _.ON U-O O.OO O O.__ OO.O + ON.O OONOOOOO + OOOOOs-OOOOXO_OI O-O O.N O N._ O O._ O-O O.ON O-O _.OO O N.OO OO.O + ON.O OOOOOO_OOOO + OOOOOE-OOOOxOOO: O-O N.N O-O O.N O-O 0.0 O O.OO O O.OO O O.NO ON.O _OOOOe-OOOOXONO= O-O O.N O N._ O-O O._ O O.OO O O.OO O O.ON OO.O + NO.O OONOOOOO + _OOOOO-OOOOXOOO= O-O O.N O N._ O-O O._ O O.OO O O.OO O O.O OO.O + NO.O OOOOOOPOOOO + _OOOOO-OOOOXO_OI O O.O O O.O O O.O O O.OO O-O O.OO O O.OO NO.O OOOOOE-OOOOXO_OI - ----- --------------O ------- ------ ----------- NOONOOO OOOz poocm OEONOOO Om>OwO Owg< OOH mpOm ucmEpOwLO OOOO OOOEm NozoO .ONO OOOO O pcOmpcOmeO Oum>oomm 0 OF op :oOuOoOPOOO Nmme ; «OF OOONOOOOOU cw FOOOOE-OomxxOPOO-o OF .OOOOOFO OOOOONO we :oOpOOOFOcOcu OcO :oOpOcoOO< .— ONOOO 138 present. At the higher rates of haloxyfop-methyl application, herbicide combination treatment effects were not as prevalent in the treated area and lower leaves, although at the highest rate bentazon caused retention of L4C'h1the treated areas. 'These results are consistant with those seen by the author in the field where reduced control of quackgrass due to tank-mixing broadleaf and grass herbicides were overcome by increasing the application rate of the grass herbicide. In addition, the data expressed are percent of the amount of 14C recovered and this percentage is relatively constant with the three rates of applied haloxyfop-methyl. 'Therefore, the total amount of haloxyfop-methyl within a quackgrass plant would be greater at the higher rates since more total haloxyfop-methyl was available for abosrption and translocation. Autoradiographs show darker images in the treated areas on plants in which acifluorfen and bentazon were applied with the 0.07 kg/ha rate of haloxyfop-methyl than when haloxyfop-methyl was applied alone (Figures 2, 3 and 4). This indicated reduced translocation out of the teated area as depicted in Table 1. However, the autoradiography was not sensitive enough to show the reduced translocation to the lower leaves when acifluorfen and bentazon were present in combination with haloxyfop-methyl. All autoradiographs show that the 14C translocated throughout the entire plant. It is interesting to note darker labeling at the tip of the small shoot which is a region of high meristematic activity. This is seen in all three autoradiographs. Figure 2. 139 Distribution of I4C-haloxyfop-methyl 144 h after treatment of plant receiving an application of haloxyfop-methyl plus crop oil concentrate at 0.07 kg/ha plus 2.3 L/ha, respectively. Top - plant; Bottom - autoradiographs. Arrow denotes treated area. 140 141 Figure 3. Distribution of 14C—haloxyfop-methyl 144 11 after treatment of plant receiving an application of haloxyfop-methyl plus acifluorfen plus crop oil concentrate at 0.07- plus 0.56 kg/ha plus 1.2 L/ha, respectively. Top - plant; Bottom - autoradiograph. Arrow denotes treted area. 142 Figure 4. 143 Distribution of 14c haloxyfop-methyl 144 h after treatment of plant receiving an application of haloxyfop-methyl plus bentazon plus crop oil concentrate at 0.07- plus 0.84 kg/ha plus 2.3 L/ha, respectively. Top - plant;Bottom - autoradiograph. Arrow denotes treated area. 144 145 Pretreatment with acifluorfen and bentazon did not influence translocation of 14C-haloxyfop-methyl applied 24 h later (Table 2). However, plants were not sprayed with haloxyfop-methyl prior to treatment with 14C as in the previous experiment. Although separate experiments, it appeared that translocation of 14C from the treated area was less than when plants were sprayed with haloxyfop-methyl immediately prior 14C application. llfis suggests that haloxyfop-methyl may enhance its own translocation. The distribution 0f 14C-DPX-Y6202 is shown in Table 3. Leaf wash data shows considerably less absorption of DPX-Y6202 by quackgrass than haloxyfop-methyj. The effects of herbicide combinatkwishow further differences between the two grass herbicides. Within the low rate ULO7 kg/ha) treatments of DPX-Y6202, acifluorfen significantly reduced translocation of 14C to the leaf tip suggesting that acifluorfen reduced transpiration. Both acifluorfeneuuibentazon significantly reduced translocation of 14C to the rhizome although these differences were small and contribution to reduced control in the field is uncertain. At the middle and highest (0.28 and 1.12 kg/ha) rates of sprayed DPX-Y6202, the presence of bentazon in the application significantly reduced the absorption of 14C-DPX-Y6202 as shown by the higher activity in the leaf wash of that treatment. The basis for herbicide combination effects are evidenced when the means of the different tankmixes were averaged over the three rates of DPX-Y6202 (Table 4). Data indicated that acifluorfen reduced translocation of 14C to the leaf tip and bentazon reduced its 146 .OOOOOOOOOOO OO Fm>mp Om mgp pO OpeOO pcOFO cwsuwz OucmEpOmeu :mmzpmn Om>emmno OmmcmemOOOO pcOuOmOcmOO o: memz memspn .OFm>OpumOOme .OONO N.O OcO O.N OO mOOepcmmcom POO Ooeu Owe; OmeEchp :ONOpcmO OCO :meonFOOOOmO ‘ OOe< OOH V OOOO OOOOEOOmeO wOmO PFOEm emzoO . .pep eOmO OeOO.OOOmm.OOAOeO>OOOO OOF .:ONOucmO eo :mmeOOPOOUO we ucmEpOmeumeO O ON O Om>mmome Omng OpcOPO o“ coOpOoOFOOO emqu ; «OF OOOemxquc cw ngpm5-OowzonOO-u mo :oOuOooPOcOeO .m mPnOO OF .OONO N.O pO mquOcmucom POO Ooeu Ouwz OmeEchp memz :mweozpmme + Nomo>-xao we OpcmEpOmep OOO OONO O.N HO mOOeucmocom FOO Ooem Opwz OmeEchp memz OONOucmO + momm>uxmo OOO Nomo>uxao we OpcmEpOmehO .pmmp mche mFOOuPOE O.OOOOOO ow mcwcoeumO _m>m_ Om mOp pO acmememwu OFOOOUOOOOOOO poc meO peOO OOOFO O :Ongz OcOsz o O.OO O-O N.ON O.O.O _ O.N.Ne O N.Ne o O.OO OO.O + N_.e OONOOOOO + NONOe-XOO o-O O.OO O-O N.O O-O O.O O-O O.ON O-O O.ON o-O N.O OO.O + NO.O OOOOOOeOOOO + NONOe-xOO O-O O.OO o O.O O N._ O-O O.ON O-O O._O o-O O.OO NO.O NONOe-XOO o-O O.OO o-O O.O O _._ O-O O.ON O O.N_ o-O O.O OO.O + ON.O OONOOOOO + NONOe-xOO O-O O.OO o-O O.O O O.O O-O O.ON o-O O.OO O-O O.O OO.O + ON.O OOOOOOOOOOO + NONOe-XOO O O.NO o O.O O-O O.O O-O O.ON O-O O.Oe o-O O.Oe ON.O NONOe-XOO O ..OO O-O O.O O ..e O-O O.NN o-O N.ON O-O O.O OO.O + NO.O OONOOOOO + NONOe-XOO O N.OO o-O O.O O O.O O O.OO o-O O.NN O O.N OO.O + NO.O OOOOOOOOOOO + NONOe-XOO O O.OO o O.O O O.N O-O O.O_ o O.ON O-O O.__ NO.O NONOe-XOO ----------------------------- O--------------- NOONOOO OOOz pooOm _ mEONOOm , Om>OmO Ome< Ow» muOm ucmsuOmeO eOmO FPOEO - .i .. .. _ emzoO .pep wOmO O peOO OOOFO OO Oem>oumm ow? .OOOOOFO OmpOmep op :oOuOOONOOO empeO O OON OOOemxuOOc cw Nomo>-xao-u mo :oOpOmoPOOOep OcO :oOquoOO< .m mFOOO c— 148 mFOOpFOE O.OOOOOO Op chOeOOOO .mpOeucmmcoo FOO Ooeo n uooO .ummp mche Pm>m_ Om mOu uO pcmemewwu OFOOOOOewcmOO poc meO ueOO HOOPO O :OOpwz OcOsz O N.NO O 0.0 O 0.0 O 0.00 O 0.0e O O.e_ OONO O.N + O0.0 OOO + OONOOOOO O 0.00 O 0.0 O _._ O 0.0N O 0.0N O 0.0 OONO NOe + O0.0 OOOO + OOeeOOeeOOO O _.OO O 0.0 O 0.0 O O._N O O.NN O 0.00 OONO O.N OOOOOOOOOOO OOO Oon ------------------------------ O---------------- NOONOOO OOOO, OOOOO, OEONOOOH1.. OO>OOO, OOe< OOO OOOO xOEOOOe lmOmO FFOEm emBOO .peO mOmO OeOO_OOO_O OO OeO>OOOO OS .OOpcOFO OmpOmep 0O :oOuOuOPOOO emme O «OF .OmeEchp mmeOp OOFO Nomo>uxmo Oo OmpOe mmeOp em>o OmmOem>O Nomo>ixaouo mo :oOpOooFOcOeu OOO coOquoOO< .O mPOOH «— 149 absorption. Both broadleaf herbicides resulted in reduced translocation 0f 14C to the rhizome and small shoot, although these differences are very small. Autoradiography does not clearly depict these differences (Figures 5, 6, 7L However, less 14C-DPX-Y6202 translocated throughout the quackgrass than did 14C-haloxyfop-methyl since whole-plant images of the former are lighter than with the latter (Figures 5, 6 and 7 vs. 2, 3 and 4). This is undoubtedly due to the lower levels of absorption of 14C-DPX—Y6202 compared to 14C-haloxyfop-methyl. However, previous field results obtained by the author indicate very similar quackgrass activity with both compounds. This suggests that DPX-Y6202 is a more phytotoxic molecule than haloxyfop-methyl since it is just as active on quackgrass although less was absorbed. AS with MC-haloxyfop-methyl, pretreatment with acifluorfen and bentazon also did not influence translocation of 1i"C«DPX-Y6202 which was applied 24 h later (Table 5). However, 24 h treatment with acifluorfen and bentazon reduced quackgrass control with both DPX-Y6202 and haloxyfop-methyl in field trials by the author. SUMMARY Patterns of absorption and translocation of 14C-haloxyfop-methyl and 14C-DPX-Y6202 were determined hiquackgrass plants treatediuith several rates of the respective grass herbicides applied with and without the broadleaf herbicide acifluorfen and bentazon. Figure 5. 150 Distribution of 14C-DPX-Y6202 144 h after treatment of plant receiving an application of DPX—Y6202 plus crop oil concentrate at 0.07 kg/ha plus 2.3 L/ha, respectively. Top - plant; Bottom - autoradiograph. Arrow denotes treated area. 151 Figure 6. 152 Distribution of i4C-DPX-Y6202 144 h after treatment of plant receiving an application of DPX-Y6202 plus acifluorfen plus crop oil concentrate at 0.07 - plus 0.56 kg/ha plus 1.2 L/ha, respectively. Top - plant; Bottom autoradiograph. Arrow denotes treated area. 153 ‘a {.-: _ 1,! .. i" \ Figure 7. 154 Distribution of 14c-DPx—Y6202 144 h after treatment of plant receiving an application of DPX-Y6202 plus bentazon plus crop oil concentrate at 0.07 - plus 0.84 kg/ha plus 2.3 L/ha, respectively. Top - plant; Bottom - autoradiograph. Arrow denotes treated area. 155 156 Pm>m_ Om mOO OO OOeOO “OOPO :OOpwz OpcmEpOmep :mmzme Om>emOOo Omm:memeOOO ucOmwwwcmOO o: memz memOO .OOOOOOOOOOO OO O .O_m>wpomOOme .OONO N.O O:O O.N OO mpOepcmu:Ou FOO Ooem ONO: OmeEO:Op :ONOp:mO O:O :meeOOFwOOOmO. Ome< OOH mpOO Ou:mEpOmeumeO eOmO PFOEm emzoO .pe» mOmO peOa O:OPO,OO Oem>oomm OO— .:ONOO:mO eo :mweoOFmOuO we pcmEpOmeumeO O ON O Om>Omume OOOOz OucONO o» :oOuOmOFOOO empOO O OOF OOOemOUOOO :O Nomo>uxaoio we :OOOOOOFOOOeO .m m—OOO OF 157 A major difference between the two labeled herbicides was observed in the amount of 14C absorbed as considerably more 14C-haloxyfop-methyl was absorbed by the treated quackgrass leaves than 14c-DPX—Y6202. Reduced translocation of 14C-haloxyfop-methyl out of the treated area and into the lower leaves was observed in plants treated with haloxyfop-methyl and acifluorfen at 0.07 plus 0.56 kg/ha plus crop oil concentrate at 1.3 L/ha. However, this effect was not seen in plants treated with higher rates of haloxyfop-methyl. When averaged over rates of DPX-Y6202 application, acifluorfen reduced translocation of 14C-DPX-Y6202 from the treated area to the tip of the treated leaf and bentazon reduced its absorption into treated quackgrass plants. However, with both herbicides, acifluorfen and bentazon did not have a large effect on translocation of 14C to the rhizome and small shoot on the rhizome. These reductions in translocation may partially explain the reduction in quackgrass control observed in the field when acifluorfen and bentazon are added to certain applications of postemergence grass herbicides. LITERATURE CITED Holm, L. G., D. L. Plucknett, J. V. Pancho and J. P. Herberger. 1977. The World's Worst Weeds, Distribution and Biology. Univ. Press. Hawaii. 609 pp. Kells, J. J. 1982. Grass control in soybeans (81 cine max_(L.) Merr.) with selective postemergence herbicides. Ph.D. Dissertation. Michigan State University. 122 pp. Kells, J. J., W. F. Meggitt and D. Penner. 1981. Factors influencing grass control with selective postemergence herbicides. Proc. North Central Weed Control Conf. 36:21—22. Putnam, A. R. and D. Penner. 1974. Pesticide interactions in higher plants. Residue Rev. 50:73-110. Rhoades. Jr., G. N. and H. D. Coble. 1982. Interaction of sethoxydim and bentazon. Proc. South. Weed Sci. Soc. 35:346. Williams, C. S. and L. M. Was. 1983. The interaction of bentazon and haloxyfop or sethoxydim. Proc. North Central Weed Control Conf. 38:41. Woldetatios, T. and R. G. Harvey. 1980. Effects of bentazon, diclofop and bentazon plus diclofop on the uptake of C-bentazon and C-diclofop in corn, giant foxtail and soybeans. Abstr. Weed Sci. Soc. Am. p. 102. 158 CHAPTER 6 SUMMARY AND CONCLUSIONS Field trials were conducted in 1982 and 1983 for the evaluation of total postemergence weed control systems compared to conventional systems. In the control of annual weeds, postemergence systems were generally not as effective as standard preemergence applications. Numerous factors influenced control obtained with a total postemergence approach. One of these was the ability to make herbicide applications at the proper plant growth stage» Weeds must be treated before they become too large to be controlled or before interference causes yield reduction. Weather and other farm priorities may influence proper timing. It may also be that while one particular group of weeds are in the proper growth stage for application, others may be too small or not yet emerged as in the case of common lambsquarters in the 1982 study. Knowledge of weeds present, particularly broadleaves, is important since different herbicides controlled different weeds. However, postemergence applications can fit into a system in several ways. Often inadequate rainfall occurs for the activation of preemergence applied herbicides such that weeds escape control. In addition, in large acreages of soybeans, many times the grower is 159 160 unable to complete preemergence applications prior to weed emergence. In these instances, postemergence weed control can be very useful. In addition, there are various species of broadleaved and grass weeds not easily controlled with soil applied herbicides that are controlled with a particular postemergence herbicide. Thus, that postemergence weed control can fit into a program where needed rather than be relied upon as the only means of weed control. It is shown with quackgrass, that tillage, crop rotation, and tank-mixes can influence control with both non-selective and the selective postemergence herbicides. Generally, longer and more effective quackgrass control was obtained with non-selective herbicide applications. However, again the postemergence herbicides offer the grower other options for his system. It is often impractical to make non-selective applications in the temperate North due to weather slowing quackgrass growth in the spring, early frosts in the fall, or time constraints. In other cases, a grower may not realize the severity of a quackgrass infestation until after the soybeans have emerged. The postemergence grass herbicides offer solutions in these and other situations. In most instances with postemergence grass herbicides it was demonstrated that despite poor control of quackgrass regrowth in the late season, adequate control was obtained in the early season so that maximum yields were obtained. HowevemO grower satisfaction may be affected by the potentially large fall weed infestation in a field that received expensive herbicide applications. Growers [nay not be convinced that yields are not greatly affected by late season growth. 161 Tankmixes of acifluorfen and bentazon with postemergence grass herbicides often reduced control of quackgrass, particularly in the late season. These two herbicides were shown to differentially affect absorption and translocation of 14C-haloxyfop-methyl and DPX-Y6202 which may partially explain this antagonism. However, these tankmixes did not significantly affect soybean yields since the reduced control was not manifested until late season. In conclusion, it is important to realize that weed control is subject to numerous influences. Therefore, weed control measures should be matched to growers total agronomic system while considering the economics of such applications. ”I1111117111111111“