GLYPHOSATE AND PYRITHIOBAC (STAPLE ) COMBINATIONS IN ROUNDUP READY COTTON

Transcription

1 GLYPHOSATE AND PYRITHIOBAC (STAPLE ) COMBINATIONS IN ROUNDUP READY COTTON Mrilyn R. McClellnd, Jim L. Brrentine, nd Oscr C. Sprks 1 RESEARCH PROBLEM The Roundup Redy (glyphoste-tolernt) system hs provided cotton producers verstility in their weed mngement progrms nd llows the reduction of soilpplied herbicides in some situtions. However, glyphoste (Roundup UltrMx, Touchdown I.Q., Glyphomx, nd others) does not hve residul ctivity, nd some weeds, such s the morningglory species, re difficult to control with glyphoste lone. ple (pyrithiobc) ppers to be good choice s tnk-mix prtner for glyphoste becuse it does hve some residul ctivity nd is ctive on pitted nd entirelef morningglories. The objective of this reserch ws to determine if dding ple to glyphoste would increse weed control in Roundup Redy cotton nd provide residul control lcking in glyphoste lone. BACKGROUND INFORMATION Glyphoste progrms without residul, soil-pplied herbicides cn be used effectively under some conditions, lthough ppliction timing is importnt nd some weeds re difficult to control with glyphoste lone. udies hve been conducted to determine if pplying ple with glyphoste cn enhnce weed control over tht with glyphoste lone (Reynolds et l., 1998; Webster nd Bughmn, 1998). Miller et l. (1999) reported tht pyrithiobc incresed control of brnyrdgrss, hemp sesbni, nd pitted morningglory over tht with low rtes of glyphoste (0.188 lb ctive ingredient [i]/cre). However, sicklepod, smooth pigweed, nd entirelef morningglory were controlled eqully by ll tretments. Entirelef morningglory nd common cocklebur were controlled s well with two pplictions of glyphoste t 1 lb i/cre s with sequentil tretments of ple plus glyphoste (Webster nd Bughmn, 1998). A combintion pckge of ple nd glyphoste (ple Plus ) ws introduced by 1 Senior reserch ssocite, professor/hed, nd grdute ssistnt, Deprtment of Crop, Soil, nd Environmentl Sciences, Fyetteville. 147

2 AAES Reserch Series 497 DuPont in Gillhm et l. (2001) climed tht studies in 2000 showed tht control with the mixture ws better thn control with either herbicide lone, lthough comprisons with sequentil glyphoste tretments were not reported. RESEARCH DESCRIPTION Two sets of experiments were conducted. The first set, glyphoste formultion experiments, ws conducted in 2001 t Mrinn nd Fyetteville, AR, to evlute single pplictions of ple with four glyphoste formultions. The experiment t Mrinn ws rndomized complete block (RCB) design with 13- by 40-ft plots nd four replictions. Cotton (Pymster 1218BR) ws plnted 14 My, nd postemergence (POST) tretments were pplied 6 June (two-lef cotton, ~one-lef weeds). At Fyetteville, fourteen species cotton (Pymster 1218BR), soyben (Roundup Redy), brnyrdgrss, seedling johnsongrss, lrge crbgrss, sunflower, velvetlef, sicklepod, hemp sesbni, prickly sid, entirelef nd pitted morningglory, smooth pigweed, nd Plmer mrnth were plnted in multispecies design in 6.5-ft wide plots. Tretments were pplied 6 July (one-lef cotton stge). Glyphoste formultions were Roundup (no surfctnt), Roundup Ultr, nd Roundup UltrMx t 0.75 lb i/ cre, nd Touchdown t 0.56 lb cid equivlent/cre. Ech formultion ws pplied lone nd with ple (0.031 lb i/cre). The second set of experiments, ple Plus experiments, were conducted in 2000 nd 2001 t Mrinn nd Fyetteville to evlute ple Plus (ple + Roundup without surfctnt) progrms. Pymster 1218 Roundup Redy cotton ws plnted in mid-my. Ech experiment ws n RCB design with four replictions. Plots were 13 by 40 ft. t Mrinn nd 3 by 27 ft t Fyetteville. Tretments, rtes, nd timing re shown in Tble 1. ndrd field-plot techniques were used. Plots were rted for weed control nd cotton injury, nd cotton yield ws tken t Mrinn in Dt were nlyzed by nlysis of vrince, nd mens were seprted with Fisher s protected LSD t the 0.05 level of probbility. RESULTS Formultion Experiments Glyphoste formultions generlly did not differ in ctivity in the formultion experiments (dt not shown), nd only dt for ple with Roundup Ultr nd Touchdown re shown (Tble 2). The benefits of dding ple to glyphoste were evident with these single-ppliction tretments. Control of prickly sid (Sid spinos), morningglory species (Ipomoe lcunos nd I. hederce vr. integriuscul ), pigweed species (Amrnthus plmeri nd A. hybridus), nd nnul grsses (Digitri 148

3 Summries of Arknss Cotton Reserch, 2001 snguinlis, Eleusine indic, nd Brchiri pltyphyll) t 4 weeks fter tretment (WAT) t Mrinn ws 89 to 100% with ll tretments. By 13 WAT, however, control with glyphoste lone ws significntly lower for ll species. Control with glyphoste lone lso declined t Fyetteville for most species s weed regrowth nd lte emergence occurred (Tble 3). Becuse of good soil moisture nd high tempertures, plnt growth nd herbicide ctivity were rpid, nd control ws evident even by 1 WAT. Regrowth of species ws rpid s well, nd weed control hd declined by 4 WAT. In the ple Plus experiments, cotton ws injured slightly by ple pplied preemergence (PRE) lone or with fluometuron (Fig. 1). Although erly symptoms (3 to 7 DAT) included slight chlorosis, injury t 2 WAT mnifested primrily s stunting. No visul injury ws noted lter in the seson except t Mrinn in 2000 from ple + fluometuron PRE fb full rte of ple postemergence [12% t 6 weeks fter lte overthe-top () tretment]. Seedcotton yield (Mrinn 2001) did not differ mong tretments (dt not shown). Prickly sid control ws 95% t 2 WAT with ll tretments (Fig. 2). By 7 WAT, control with Roundup Ultr lone ws lower thn control with tretments contining pyrithiobc. The decline ws due to decresed control t Mrinn (72% t 7 WAT), wheres control t Fyetteville did not differ mong tretments (dt not shown). ple Plus pplied lone gve the poorest morningglory control initilly t both Fyetteville nd Mrinn (Fig. 3). By 7 WAT, control hd incresed with single pplictions nd decresed with erly over-the-top (EOT) pplictions. Morningglories treted t EOT pprently hd sufficient regrowth to void complete shding from the growing cotton, wheres those treted t were further shded by the cotton. Control lso declined with Roundup Ultr pplictions nd ws lower thn tretments in which ple or ple Plus ws pplied. For this difficult-to-control species, the residul ctivity of ple helped mintin control lter into the seson. Pigweed species were controlled 99 to 100% t 2 weeks fter tretments nd 96% t 7 WAT (dt not shown). Miller et l. (1999) reported 98 to 100% control t 7 WAT with sequentil pplictions of Roundup Ultr lone or with single or sequentil pplictions of Roundup Ultr + ple. Annul grss ws controlled 100% t 2 weeks fter tretments with ll tretments (dt not shown). At 7 weeks fter tretments, control ws 93% except with the sequentil ppliction of Roundup Ultr, which gve only 84% t Mrinn. ple, lthough generlly wek on grsses, ppered to hve enough residul ctivity to help mintin grss control. At Fyetteville, however, control ws 100% with Roundup Ultr lone, nd lter-emerging grss ws shded by the cotton cnopy. PRACTICAL APPLICATION Adding ple to glyphoste postemergence (ple Plus), or pplying ple preemergence prior to glyphoste ppliction, my be dvntgeous for difficult-tocontrol species such s morningglories, especilly with high-density infesttions nd 149

4 AAES Reserch Series 497 with single pplictions prior to lte post-directed or lyby tretments. The cost of the dditionl ple will hve to be blnced with the benefits of possible incresed nd residul control from ple nd will depend on the species nd density of weeds present or nticipted in the crop. LITERATURE CITED Gillhm, L., S. Willims, A. Yng, nd J Clus Weed control in Roundup Redy cotton with ple Plus. Proc. Beltwide Cotton Conf., Ntionl Cotton Council, Memphis, TN. (vol. 2) p McClellnd, M Roundup Redy cotton weed control systems. In: D. Oosterhuis (ed.). Proc. Cotton Reserch Meeting nd Summries of Reserch in Progress. University of Arknss Agriculturl Experiment tion Specil Report 188: Miller, C., C. Wilson, nd J. Millign Evlution of Roundup Ultr/ple combintions for totl postemergence weed control in Roundup Redy cotton. Proc. Beltwide Cotton Conf., Ntionl Cotton Council, Memphis, TN. (vol. 1) p Reynolds, D., C. Rowlnd, R. Cobill, nd K. Bloodworth Evlution of ple use in trnsgenic cotton. Proc. Beltwide Cotton Conf., Ntionl Cotton Council, Memphis, TN. (vol. 1) p Webster, E. nd T. Bughmn rtegies for ple use in cotton. Proc. Beltwide Cotton Conf., Ntionl Cotton Council, Memphis, TN. (vol. 1) p Tble 1. Tretments in ple Plus experiments, Mrinn nd Fyetteville, Tretment Appliction designtion Herbicide z Rte timing y (lb i/cre) ple PRE fb fluometuron fb 0.94 fb ple Assure (quizlofop) ple PRE fb fluometuron fb 0.94 fb ple Plus ple fb fb PRE fb ple Plus EOT ple Plus EOT ple Plus EOT/ ple Plus EOT fb RU/RU Roundup Ultr(Mx) 0.75 EOT fb z ple = pyrithiobc + NIS (surfctnt); ple Plus + pyrithiobc + glyphoste + NIS; fb = followed by. y PRE = preemergence; EOT = cotyledon- to 3-lef; = 4-lef cotton. 150

5 Summries of Arknss Cotton Reserch, 2001 Tble 2. Control of prickly sid, morningglory species (pitted nd entirelef), nd nnul grsses t 4 nd 13 weeks fter tretment (WAT) t 2-lef cotton nd seedcotton yield, Mrinn, Prickly sid Morningglory spp. Annul grss Lint Tretment z 4 WAT 13 WAT 4 WAT 13 WAT 4 WAT 13 WAT yield (%) (lb/cre) + RU 100 y b TD b RU 89 b 40 b 88 c 69 b TD 89 b 53 b 91 bc 70 b b 1480 z = ple; RU = Roundup UltrMx; TD = Touchdown. RU nd TD re glyphoste formultions. y Mens for ech species t ech rting followed by the sme letter do not differ by LSD Tble 3. Control of prickly sid, entirelef morningglory, brnyrdgrss, nd sicklepod t 1 nd 4 weeks fter tretment (WAT) t 2-lef cotton, Fyetteville, Entirelef Prickly sid morningglory Brnyrdgrss Sicklepod Tretment z 1 WAT 4 WAT 1 WAT 4 WAT 1 WAT 4 WAT 1 WAT 4 WAT (%) RU 100 y b TD b RU 89 b 40 b 88 c 69 b b TD 89 b 53 b 91 bc 70 b b b z = ple; RU = Roundup UltrMx; TD = Touchdown. RU nd TD re glyphoste formultions. y Mens for ech species t ech rting followed by the sme letter do not differ by LSD % Injury b b EOT c c c c EOT/ * mens with the sme letter do not differ significntly. RU/RU Fig. 1. Cotton injury 2 wks fter pplictions, men of 2000 nd 2001, Fyetteville nd Mrinn, AR (tretments listed in Tble 1). 151

6 AAES Reserch Series 497 PRICKLY SIDA CONTROL 100 b b 80 b % Control WAT 7 WAT 20 0 EOT ST+ EOT/ RU/RU Fig. 2. Prickly sid control 2 nd 7 weeks fter tretment (WAT), men of 2000 nd 2001, Fyetteville nd Mrinn, AR (tretments listed in Tble 1). PITTED MORNINGGLORY CONTROL * b b b b b b d c c 80 % Control WAT 7 WAT 20 0 EOT ST+ EOT/ RU/RU *mens t ech rting time followed by the sme letter do not differ by LSD (0.05) Fig. 3. Pitted morningglory control 2 nd 7 weeks fter tretments (WAT), men of 2000 nd 2001 t Fyetteville nd Mrinn, AR (tretments listed in Tble 1). 152