Use of Imazosulfuron in Herbicide Programs for Drill-Seeded Rice (Oryza sativa) in the Mid-South United States

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Use of Imazosulfuron in Herbicide Programs for Drill-Seeded Rice (Oryza sativa)in the Mid-South United StatesAuthor(s): Dilpreet S. Riar and Jason K. NorsworthySource: Weed Technology, 25(4):548-555. 2011.Published By: Weed Science Society of AmericaDOI: http://dx.doi.org/10.1614/WT-D-11-00062.1URL: http://www.bioone.org/doi/full/10.1614/WT-D-11-00062.1

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Use of Imazosulfuron in Herbicide Programs for Drill-Seeded Rice (Oryzasativa) in the Mid-South United States

Dilpreet S. Riar and Jason K. Norsworthy*

Research was conducted in 2009 and 2010 to evaluate influence of imazosulfuron rate and application timing onweed control in drill-seeded rice at Stuttgart, AR, and to evaluate imazosulfuron-containing herbicide programs indrill-seeded rice at Keiser and Stuttgart, AR. Weed species evaluated included barnyardgrass, broadleaf signalgrass,hemp sesbania, and yellow nutsedge. Imazosulfuron applied at 224 and 336 g ai ha21 during PRE, early POST(EPOST), or preflood (PREFLD) growth periods provided similar control of all weeds. Imazosulfuron appliedEPOST or PREFLD controlled hemp sesbania and yellow nutsedge $ 93% both years at 5 and 7 wk after planting(WAP), except in 2009 when hemp sesbania control was # 79% at 7 WAP. In 2010, because of inadequate rainfall,hemp sesbania and yellow nutsedge control with PRE-applied imazosulfuron was #29% at 5 and 7 WAP.Imazosulfuron plus clomazone PRE followed by (fb) quinclorac plus propanil EPOST and imazosulfuron plusquinclorac EPOST fb thiobencarb plus propanil PREFLD programs controlled hemp sesbania and barnyardgrass (inat least two site-years), and yellow nutsedge and broadleaf signalgrass (in at least one site-year) greater than or equalto clomazone plus quinclorac PRE fb propanil plus halosulfuron PRELD (standard program). No rice injury wasobserved with any herbicide program. Rice yield with all imazosulfuron-containing herbicide programs (6,630 to8,130 kg ha21) was similar to the standard herbicide program (7,240 kg ha21). Imazosulfuron in mixture withclomazone, propanil, or quinclorac can be incorporated into herbicide programs of mid-South rice production forthe control of broadleaf weeds and sedges.Nomenclature: Clomazone; halosulfuron; imazosulfuron; propanil; quinclorac; thiobencarb; barnyardgrass, Echinochloacrus-galli (L.) P. Beauv.; broadleaf signalgrass, Urochloa platyphylla (Griseb.) Nash.; hemp sesbania, Sesbania herbacea (P.Mill.) McVaugh; yellow nutsedge, Cyperus esculentus L.; rice, Oryza sativa L.Key words: Herbicide programs, residual weed control, rice, V-10142.

En 2009 y 2010 se realizo una investigacion para evaluar la influencia de la dosis y el momento de aplicacion deimazosulfuron en el control de malezas en el cultivo de arroz sembrado en lıneas en Stuttgart, AR, y tambien para evaluarlos programas que utilizan este mismo herbicida en arroz sembrado de la misma manera en Keiser y Stuttgart, AR. Lasespecies de maleza evaluadas incluyeron Echinochloa crus-galli, Urochloa platyphylla, Sesbania herbacea y Cyperus esculentus.Imazosulfuron aplicado a 224 y 336 g ia ha21 durante PRE, POST-temprana (EPOST), o antes de la inundacion(PREFLD) proporciono control similar de todas las malezas. Imazosulfuron aplicado EPOST o PREFLD controlo S.herbacea C. esculentus $93% en ambos anos a las 5 y 7 semanas despues de la siembra (WAP), excepto en 2009 cuando elcontrol de S. herbacea fue #79% a las 7 WAP. En 2010, debido a la escasez de lluvias, el control de S. herbacea y C.esculentus con imazosulfuron aplicado PRE fue #29% a las 5 y 7 WAP. Los programas en que se aplico imazosulfuron masclomazone en PRE seguido de (fb) quinclorac mas propanil en EPOST e imazosulfuron mas quinclorac en EPOST fbthiobencarb mas propanil en PREFLD, controlaron S. herbacea y E. crus-galli (en al menos dos anos/sitio), y C. esculentus yU. platyphylla (en al menos un ano/sitio) mejor o igual al clomazone mas quinclorac PRE fb propanil mas halosulfuronPREFLD (programa estandar). No se observo dano en el arroz con ninguno de los programas de herbicidas. Elrendimiento del arroz en todos los programas de herbicidas con imazosulfuron (6630 a 8130 kg ha21) fue similar alprograma de herbicidas estandar (7240 kg ha21). Imazosulfuron mezclado con clomazone, propanil, o quinclorac puedeser incorporado a los programas de herbicidas para la produccion de arroz en la region Sur-Media para el control demalezas de hoja ancha y cyperaceas.

Effective weed management is a key to successful riceproduction. Barnyardgrass, red rice, broadleaf signalgrass,yellow nutsedge, and hemp sesbania are among the mostproblematic weeds of rice (Kwon et al. 1991; Norsworthyet al. 2007; Zhang et al. 2006). Barnyardgrass and broadleafsignalgrass interfere with rice mainly early in the season;whereas, hemp sesbania and red rice interfere during mid- tolate season (Smith 1988). Season-long interference of red rice,

barnyardgrass, broadleaf signalgrass, and hemp sesbania cancause 19 to 82% reduction in rice yield (Kwon et al. 1991;McGregor et al. 1988; Smith 1968, 1974, 1981, 1988).

Direct dry-seeding is the most common method ofestablishing rice in Arkansas, representing 97% of the ricearea in the state (Slaton and Cartwright 2010). Seeding isfollowed by permanent flooding at the beginning of tilleringstage, approximately 4 to 5 WAP (Tacker et al. 2010).Continuous flooding reduces emergence and growth of mostsemiterrestrial broadleaf and grass weeds of rice (Smith andFox 1973). Controlling weeds between planting and floodingis critical for maximizing yields in dry-seeded rice (Smith andHill 1990).

DOI: 10.1614/WT-D-11-00062.1* Postdoctoral Research Associate and Associate Professor, Department of

Crop, Soil, and Environmental Sciences, University of Arkansas, 1366 WestAltheimer Drive, Fayetteville, AR 72704. Corresponding author’s E-mail:[email protected]

Weed Technology 2011 25:548–555

548 N Weed Technology 25, October–December 2011

Numerous herbicides are available for PRE and POSTweed control in rice. Pendimethalin, clomazone, quinclorac,and thiobencarb have residual activity and are commonlyapplied PRE or delayed-PRE (Jordan et al. 1998; Norsworthyet al. 2007). Imazethapyr is another residual herbicide that issolely registered for use in imidazolinone-resistant (Clear-fieldTM) rice (Avila et al. 2005; Masson et al. 2001). Propanilis a common POST herbicide, usually applied in combinationwith residual herbicides (Crawford and Jordan 1995; Jordan1997; Norsworthy et al. 2010; Smith and Hill 1990).

Imazosulfuron, a new herbicide developed by ValentHUSA, has recently been registered for use in U.S. rice.Imazosulfuron inhibits acetolactate synthase (EC 4.1.3.18)activity at very low concentrations (imazosulfuron concentra-tion required to inhibit acetolactate synthase activity by 50%5 circa 1028 mol L21) and hinders biosynthesis of branched-chain amino acids (Usui 2001). Imazosulfuron does notrequire mechanical incorporation into the soil (Felix andBoydston 2010). It primarily controls broadleaf weeds andsedges (Baron 2006). In potato (Solanum tuberosum L.),sequential applications (PRE fb POST) of imazosulfuronat 336 g ai ha21 controlled yellow nutsedge, commonlambsquarters (Chenopodium album L.), redroot pigweed(Amaranthus retroflexus L.), and Powell amaranth (Amaran-thus powelli S. Wats.) (Felix and Boydston 2010) $92%. TwoPOST applications of imazosulfuron at 560 g ha21 controlledyellow nutsedge $ 90% in bermudagrass [Cynodon dactylon(L.) Pers.] (Henry and Sladek 2008). Imazosulfuron inmixture with bispyribac-sodium or penoxsulam effectivelycontrolled texasweed [Caperonia palustris (L.) St. Hil.] in drill-seeded rice (Godara 2010).

In rice, imazosulfuron is primarily metabolized by O-demethylation as well as hydroxylation of the aromatic ringand alkyl chain fb complete detoxification by glucose con-jugation of hydroxyl groups (Usui 2001). Imazosulfurondegradation in soil is temperature and pH dependent, and thehalf-life of imazosulfuron decreases under high temperatureand acidic conditions (Moricca et al. 2001b). The half-life ofimazosulfuron was 3.3 to 6 d at pH , 4 compared to 578 dat pH 5.9. Additionally in sandy loam soils, imazosulfuronhalf-life under aerobic and anaerobic conditions was 70 and4 d, respectively (Morrica et al. 2001b). Depending upon soilcharacteristics and weather conditions, imazosulfuron can beincorporated into herbicide programs in rice for residual early-season control of broadleaf weeds and sedges (Felix andBoydston 2010; Godara 2010; Henry and Sladek 2008;Morrica et al. 2001a,b). A study was conducted withobjectives to (1) determine the effect of imazosulfuron rateand timing of application on weed control in rice and(2) evaluate imazosulfuron-containing herbicide programs indrill-seeded rice.

Materials and Methods

Imazosulfuron Rate and Timing. To determine the effect ofimazosulfuron rate and timing of application on weed controlin rice, field experiments were conducted at the Rice Researchand Extension Center near Stuttgart, AR, in 2009 and 2010.Soil was a DeWitt silt loam (fine, smectitic, thermic Typic

Albaqualfs) with a pH of 5.0. The test area was broadcast-sprayed with the potassium salt of glyphosate1 at 870 g ae ha21

1 mo prior to planting to control winter and spring annualweeds. Additionally, experimental areas were disked andcultivated before planting. Rice (cv. Wells) was drill-seeded in2- by 6-m plots on May 19, 2009, and May 5, 2010, at 19-cmrow spacing and 79 seeds m21 of row. A single row each ofbarnyardgrass, broadleaf signalgrass, hemp sesbania, Palmeramaranth (Amaranthus palmeri S. Wats.), prickly sida (Sidaspinosa L.), pitted morningglory (Ipomoea lacunosa L.), andyellow nutsedge was planted perpendicular to the rice rows inall plots. Irrigation was not applied until 3 d after PREFLDtreatments, when permanent flooding was established. Ureawas applied at preflood and 3 wk after (WA) PREFLD at 100and 50 kg N ha21, respectively.

The experiment was conducted in a randomized completeblock design with a two (imazosulfuron2 rates: 224and 336 g ha21 ) by three (application timing: PRE, EPOST,and PREFLD) factorial arrangement of treatments. Treat-ments were replicated four times. A nontreated controltreatment was also included in each year. All PRE treatmentswere applied immediately after planting, whereas EPOST andPREFLD treatments were applied at the two- to three-leaf andfour- to six-leaf stages of rice, respectively. Adjuvant3 (a blendof deposition agents, nonionic surfactants, and activators) at2.5% v/v was added to all EPOST and PREFLD treatments.Herbicide treatments were applied with a CO2-pressurizedbackpack sprayer fitted with 110015 XR flat-fan spraynozzles4 calibrated to deliver 140 L ha21 spray solution.

Weed control was visually estimated at 5 and 7 WAP on ascale of 0 to 100, where 0 is no weed control and 100 iscomplete weed control. Weed control ratings were based onfoliar chlorosis, necrosis, and stunting of plants comparedto those in nontreated plots. Negligible control of naturalpopulations of barnyardgrass and broadleaf signalgrass re-sulted in severe interference with the rice crop. Because ofpoor rice stand resulting from this interference, rice yield datawere not recorded. Palmer amaranth, pitted morningglory,and prickly sida control data were excluded from the analysesbecause these weeds had not emerged by the time of EPOSTapplications in 2010.

Residuals were tested for normality using PROC UNI-VARIATE in SAS.5 Weed control data for 5 and 7 WAP weresubjected to analysis of variance using MIXED procedure ofSAS, assigning year, imazosulfuron rate, and applicationtiming as fixed effect and replication as random effect. Meanswere separated using Fisher’s Protected LSD at a 5 0.05.

Imazosulfuron-Containing Herbicide Programs. To evalu-ate imazosulfuron-containing herbicide programs in drill-seeded rice, field experiments were conducted at the NortheastResearch and Extension Center near Keiser, AR, and at theRice Research and Extension Center near Stuttgart, AR, in2009 and 2010. Soil at Keiser was a Sharkey clay (very fine,montmorillonitic, nonacid, thermic Vertic Haplaquepts) witha pH of 6.6. Field preparation and rice planting operationswere as in the imazosulfuron rate and timing experiment. Riceplanting dates were May 19, 2009, and April 30, 2010, atKeiser, and May 19, 2009, and May 5, 2010, at Stuttgart.Urea was applied two times at Stuttgart (100 and 50 kg N ha21

Riar and Norsworthy: Rice herbicide programs N 549

at PREFLD and 3 WA PREFLD, respectively) and threetimes at Keiser (30, 100, and 50 kg N ha21 at planting,PREFLD, and 3 WA PREFLD, respectively).

Experiments were conducted in a randomized completeblock design with 12 herbicide programs and four replica-tions. Herbicide programs evaluated were imazosulfuron at224 or 336 g ha21 plus clomazone6 at 336 g ha21 PRE fbquinclorac7 at 560 g ai ha21 plus propanil8 at 4,480 g ai ha21

EPOST; imazosulfuron at 224 or 336 g ha21 plus clomazoneat 336 g ha21 EPOST fb quinclorac at 560 g ha21 pluspropanil at 4,480 g ha21 PREFLD; imazosulfuron at 224 or336 g ha21 plus quinclorac at 560 g ha21 EPOST fbthiobencarb9 at 3,360 g ai ha21 plus propanil at 3,360 g ha21

PREFLD; imazosulfuron at 224 or 336 g ha21 plus clom-azone at 336 g ha21 PRE fb quinclorac at 560 g ha21 plusimazosulfuron at 224 or 336 g ha21 PREFLD; imazosulfuronat 224 or 336 g ha21 plus clomazone at 336 g ha21 PRE fbpropanil at 4,480 g ha21 plus imazosulfuron at 224 or336 g ha21 PREFLD; and clomazone at 336 g ha21 plusquinclorac at 560 g ha21 PRE fb propanil at 4,480 g ha21

plus halosulfuron10 at 53 g ha21 PREFLD (standard herbicideprogram used in Arkansas). All POST treatments withimazosulfuron plus clomazone or quinclorac containedadjuvant (a blend of deposition agents, nonionic surfactants,and activators) at 2.5% v/v. A nontreated control was alsoincluded. PRE treatments were applied immediately afterplanting, except at Keiser in 2010, where PRE treatment wasdelayed for 6 d because of wind and rain. All EPOST andPREFLD treatments were applied at two- to three-leafand four- to six-leaf stages of rice, respectively. Herbicideapplication was similar to that in the imazosulfuron rate andtiming study.

Injury to rice plants and weed control was rated at 2 WAEPOST, 2 WA PREFLD, and 6 WA PREFLD. Late-seasonevaluations were made at 10 WA PREFLD at Stuttgart in2010. Weed control and rice injury evaluations were made ona 0 to 100 scale similar to the imazosulfuron rate and timingstudy. Weed species evaluated were barnyardgrass and hempsesbania at Keiser and Stuttgart in 2009 and 2010, broadleafsignalgrass at Stuttgart in 2009 and 2010, and yellownutsedge at Keiser and Stuttgart in 2010. Palmer amaranthand pitted morningglory populations were not present at thetime of EPOST application, except at Keiser in 2009. Thus,data for Palmer amaranth and pitted morningglory wereexcluded from all analyses. Rice yield was determined byharvesting rice at maturity from the middle four rows of eachplot with a small-plot combine. Rice yields were adjusted to12% moisture.

Residuals were tested for normality and homogeneity ofvariance prior to analyses. Data for weed control, rice injury,and rice yield were subjected to ANOVA using the MIXEDprocedure of SAS,5 considering site-year as fixed effect andreplication as random effect. Means were separated usingFisher’s Protected LSD at a 5 0.05. Additionally, standardprogram was compared to all programs containing imazo-sulfuron plus clomazone PRE fb quinclorac plus propanilEPOST (referred to as PRE fb EPOST in remaining text),quinclorac plus propanil PREFLD, thiobencarb plus propanilPREFLD, quinclorac plus imazosulfuron PREFLD, and

propanil plus imazosulfuron PREFLD using preplanned con-trasts. Preplanned contrasts were also conducted for all PREfb EPOST vs. EPOST fb PREFLD (containing clom-azone or thiobencarb); quinclorac plus propanil PREFLDvs. thiobencarb plus propanil PREFLD; quinclorac plusimazosulfuron PREFLD vs. propanil plus imazosulfuronPREFLD; and PRE fb EPOST vs. PRE fb PREFLD pro-grams. PREFLD treatments were applied following 2 WAEPOST evaluations. Therefore at 2 WA EPOST, differencebetween herbicide programs was tested based on PRE orEPOST applications only, and contrast comparisons werechanged accordingly.

Results and Discussion

Imazosulfuron Rate and Timing. There was no effect ofimazosulfuron rate and application timing on barnyardgrassand broadleaf signalgrass control (data not shown). Therewas no difference between imazosulfuron rates of 224 and336 g ha21 for hemp sesbania and yellow nutsedge control atany application timing; therefore, data on these weeds werepooled across imazosulfuron rates. Only year by timinginteraction was significant; therefore, data are presented byyear and application timing (Table 1). Hemp sesbania control5 WAP from PRE-applied imazosulfuron at 5 WAP wasgreater in 2009 (76%) than in 2010 (28%). Yellow nutsedgecontrol with PRE-applied imazosulfuron was $ 99% in 2009and # 29% in 2010 at 5 and 7 WAP. Rainfall receivedwithin 10 d of PRE application was 70 mm in 2009compared to 15 mm in 2010. Greater rainfall in turnincreased imazosulfuron activation and weed control in 2009compared to 2010.

Control of hemp sesbania (in both years) and yellownutsedge (in 2010) was greater with POST-applied thanwith PRE-applied imazosulfuron treatments (Table 1). Hempsesbania control following POST-applied treatments was$ 93% both years at 5 and 7 WAP, except at 7 WAP in2009, when control was # 79%. Yellow nutsedge control5 and 7 WAP was $ 95% following imazosulfuron at allapplication timings in 2009 and following POST applicationsin 2010. Greater than 90% yellow nutsedge and broadleafweed control by imazosulfuron (applied PRE or PRE fbPOST) has been documented in other studies (Felix andBoydston 2010; Henry and Sladek 2008).

Imazosulfuron degrades faster in soils with low pH andanaerobic conditions (Morrica et al. 2000, 2001a,b). AtStuttgart, soil pH in the experimental plots was acidic (5.0)and the months of May and June collectively accumulated349 mm rainfall in 2009 compared to 165 mm rainfall in2010. Hemp sesbania emerges in multiple flushes. Fasterdegradation of imazosulfuron due to acidic pH and greaterrainfall after planting might have decreased the control of laterflushes of hemp sesbania at 7 WAP in 2009 compared to2010 POST treatments. At Stuttgart, an imazosulfuron half-life of 3 d has been reported previously (Norsworthy et al.2011). Imazosulfuron applied PRE (in presence of adequateand timely rainfall), EPOST, or PREFLD controlled yellownutsedge $ 95%, and applied EPOST or PREFLD (under


aerobic conditions) controlled hemp sesbania $ 93% at both224 and 336 g ha21.

Imazosulfuron-Containing Herbicide Programs. WeedControl at 2 WA EPOST. There were significant treatment-site–year interactions for barnyardgrass, broadleaf signalgrass,hemp sesbania, and yellow nutsedge control at 2 WA EPOST.Thus, data are presented by site-years (Table 2). As observedin the imazosulfuron rate and timing study, all imazosulfuron-containing programs showed no rate response betweenimazosulfuron at 224 and 336 g ha21 for control of hempsesbania and barnyardgrass (in at least two out of four site-years), and yellow nutsedge and broadleaf signalgrass (one outof two site-years). PRE fb EPOST programs controlled allweed species $ 90% at each site-year, except for yellownutsedge at Stuttgart in 2010, which was controlled 33and 58% at imazosulfuron rates of 224 and 336 g ha21,respectively. PREFLD treatments had not been applied at the2 WA EPOST evaluation. Consequently, weed control in allPRE fb EPOST programs was greater than or equal to theimazosulfuron-containing programs with PREFLD applica-tions.

At Stuttgart in 2010, control of yellow nutsedge (in allprograms) and broadleaf signalgrass (in all imazosulfuron-containing EPOST fb PREFLD and PRE fb PREFLDprograms) was unsatisfactory (Table 2). Yellow nutsedgecontrol at Stuttgart in 2010 was # 58% in all programs. AtKeiser in 2010, low density of yellow nutsedge was presentduring EPOST application, and most of the yellow nutsedgeemergence was after flooding; therefore, data for yellownutsedge control at 2 WA EPOST are not presented. AtStuttgart, broadleaf signalgrass control in all imazosulfuron-containing EPOST fb PREFLD and PRE fb PREFLDprograms was # 84% in 2010 compared to $ 89% in2009. Reduced broadleaf signalgrass and yellow nutsedgecontrol at Stuttgart in 2010 was attributed to larger weeds (8to 10 leaves) at EPOST application and limited activation ofPRE-applied herbicides. Decreased yellow nutsedge controldue to the limited activation of PRE imazosulfuron atStuttgart in 2010 was also observed in the imazosulfuron rateand timing study.

Barnyardgrass control in all imazosulfuron-containingPRE fb PREFLD programs was # 76% at Keiser in 2009(Table 2). Recommended clomazone rate for clay soils is560 g ha21 (CDMS 2011). The soil at Keiser was a Sharkeyclay, and reduced barnyardgrass control with PRE-appliedimazosulfuron plus clomazone was due to a lower-than-labeled clomazone rate being used for clay soils. At Keiser,imazosulfuron plus clomazone PRE applications were delayedfor 6 d in 2010 due to rain and wind, which appears to haveprovided greater barnyardgrass control compared to 2009.Clomazone has half-life of 5 to 34 d depending upon soil andfield conditions (Kirksey et al. 1996; Mills and Witt 1989).Greater barnyardgrass control at Keiser in 2010 compared to2009 might be due to the availability of clomazone for longertime that helped to kill later flushes of barnyardgrass.

Contrast analyses revealed that control of all evaluated weedspecies in PRE fb EPOST programs was greater than or equalto clomazone plus quinclorac PRE (standard PRE) (Table 2).Hemp sesbania and yellow nutsedge control in imazosulfuronplus quinclorac EPOST treatments was also greater than orsimilar to that recorded in standard PRE. However, atStuttgart in 2010, standard PRE provided greater barnyard-grass and broadleaf signalgrass control than imazosulfuronplus quinclorac EPOST treatments. Barnyardgrass and hempsesbania control with imazosulfuron plus clomazone EPOSTor PRE (in PRE fb PREFLD programs) was less than stan-dard PRE in at least two out of four site-years. Similarly,imazosulfuron plus clomazone applied EPOST or PRE (inPRE fb PREFLD programs) controlled broadleaf signalgrassless than the standard PRE in at least one out of two site-years.Programs containing imazosulfuron plus quinclorac EPOSTand PRE fb EPOST applications controlled hemp sesbaniaand barnyardgrass (in three out of four site-years), and yellownutsedge and broadleaf signalgrass (in one out of two site-years) greater than or similar to the standard herbicideprogram.

Weed Control at 2 WA PREFLD. Significant treatment-by-site-year interactions were detected for the control of all weedspecies, except hemp sesbania, where treatment-by-yearinteractions were nonsignificant at Keiser and Stuttgart. Thus,

Table 1. Influence of imazosulfuron application timing (averaged over two rates: 224 and 336 g ai ha21) on hemp sesbania and yellow nutsedge control at Stuttgart, AR,in 2009 and 2010.a–c

Timing

Control

Hemp sesbania Yellow nutsedge

5 WAP 7 WAP 5 WAP 7 WAP

2009 2010 2009 2010 2009 2010 2009 2010

---------------------------------------------------------------------------------------------------------------------------------------------- % ---------------------------------------------------------------------------------------------------------------------------------------------PRE 76 bA 28 bB 35 cA 29 bA 99 aA 22 bB 100 aA 29 bBEPOST 97 aA 93 aA 79 aB 100 aA 98 aA 95 aA 100 aA 99 aAPREFLD —d —d 54 bB 96 aA —d —d 100 aA 100 aA

a Abbreviations: EPOST, early-POST; PREFLD, preflooding; WAP, weeks after planting.b All POST imazosulfuron treatments contained adjuvant3 (a blend of deposition agents, nonionic surfactants, and activators) at 2.5% v/v.c For each year, means within a column followed by the same lowercase letters and, for between years, means within a row followed by the same uppercase letters

(specific for each weed and evaluation time) are not significantly different according to Fisher’s Protected LSD test (a 5 0.05).d Treatment not applied at time of evaluation.


hemp sesbania control data were pooled over years at Keiserand Stuttgart, but data for all other weed species are presentedby site-years (Table 3). Similar to 2 WA EPOST, increasingimazosulfuron rate from 224 to 336 g ha21 did not affect(with few exceptions) barnyardgrass, broadleaf signalgrass,hemp sesbania, and yellow nutsedge control.

Hemp sesbania control at both Keiser and Stuttgart, andbarnyardgrass control at Stuttgart was $ 91% in all programseach year (Table 3). However at Keiser, barnyardgrass controlin imazosulfuron plus clomazone EPOST fb quinclorac pluspropanil PREFLD and PRE fb PREFLD programs variedfrom 51 to 82% and 86 to 100% in 2009 and 2010,respectively. At Keiser, barnyardgrass was large (8 to 10 leaves)at the time of PREFLD applications because of ineffectiveearly-season control following imazosulfuron plus clomazonePRE or EPOST applications, which in turn reduced

barnyardgrass control at 2 WA PREFLD. Reduced barnyard-grass control with increase in size has been reported previously(Ahmadi et al. 1980; Payne and Oliver 2000). Barnyardgrasscontrol with imazosulfuron plus quinclorac EPOST fbthiobencarb plus propanil PREFLD programs was greaterthan imazosulfuron plus clomazone EPOST fb quincloracplus propanil PREFLD programs at Keiser both years and atStuttgart in 2009. Greater control of barnyardgrass earlyin the season led to $ 90% barnyardgrass control 2 WAPREFLD in imazosulfuron plus quinclorac EPOST fbthiobencarb plus propanil PREFLD and PRE fb EPOSTprograms during each site-year.

All herbicide programs controlled yellow nutsedge 100% atKeiser and $ 85% at Stuttgart in 2010 (Table 3). However,control was lower (# 75%) in imazosulfuron plus clomazonePRE fb quinclorac plus imazosulfuron PREFLD programs at

Table 2. Hemp sesbania, barnyardgrass, yellow nutsedge, and broadleaf signalgrass control in rice at 2 WA EPOST at Keiser and Stuttgart, AR during 2009 and 2010.a,b

Treatment Timing Rate

Control

Hemp sesbania BarnyardgrassYellow

nutsedgecBroadleaf

signalgrassd

Keiser Stuttgart Keiser Stuttgart Stuttgart Stuttgart

2009 2010 2009 2010 2009 2010 2009 2010 2010 2009 2010

g ai ha21 -----------------------------------------------------------------------------------------------------------------% ---------------------------------------------------------------------------------------------------------------

Imaz + cloma fbquin + prop

PRE 224 + 336 98 100 99 98 98 100 100 97 33 100 90EPOST 560 + 4,480


PRE 336 + 336 100 98 100 93 97 98 99 100 58 100 98EPOST 560 + 4,480


EPOST 224 + 336 74 95 95 96 58 59 77 80 41 89 64PREFLD 560 + 4,480


EPOST 336 + 336 77 89 96 95 54 78 75 79 35 95 63PREFLD 560 + 4,480

Imaz + quin fbthio + prop

EPOST 224 + 560 90 88 98 94 79 93 90 73 33 99 49PREFLD 3,360 + 3,360


EPOST 336 + 560 92 95 100 94 88 100 96 78 38 97 56PREFLD 3,360 + 3,360

Imaz + cloma fbquin + imaz

PRE 224 + 336 59 41 85 58 58 85 92 82 25 98 64PREFLD 560 + 224


PRE 336 + 336 62 50 87 30 76 98 87 80 13 98 55PREFLD 560 + 336

Imaz + cloma fbprop + imaz

PRE 224 + 336 58 61 89 53 58 88 92 91 25 99 84PREFLD 4,480 + 224


PRE 336 + 336 59 63 91 58 62 88 91 85 10 99 63PREFLD 4,480 + 336

Cloma + quin fbprop + halo

PRE 336 + 560 86 51 100 97 61 45 98 96 5 100 96PREFLD 4,480 + 53

LSD (0.05)e 14 13 11 17 17 11 12 9 19 6 13

Contrastsf

Standardg vs. PRE fb EPOST (+) (+) NS NS (+) (+) NS (+) (+) NS NSStandard vs. imaz + cloma EPOST (2) (+) (2) NS NS (+) (2) (2) (+) (2) (2)Standard vs. imaz + quin EPOST NS (+) NS NS (+) (+) NS (2) (+) NS (2)Standard vs. PRE fb PREFLD (2) NS (2) (2) NS (+) (2) (2) (+) NS (2)

a Abbreviations: EPOST, early-POST; fb, followed by; PREFLD, preflooding; WA, weeks after; cloma, clomazone; halo, halosulfuron; imaz, imazosulfuron; NS,nonsignificant at a 5 0.05; prop, propanil; quin, quinclorac; thio, thiobencarb.

b All POST treatments with imazosulfuron plus clomazone/quinclorac contained adjuvant3 (a blend of deposition agents, nonionic surfactants, and activators) at 2.5%v/v.

c Yellow nutsedge was absent at Keiser and Stuttgart during 2009, and a low density was present at the time of EPOST applications at Keiser in 2010. Thus, for 2 WAEPOST, yellow nutsedge control is presented only for Stuttgart in 2010.

d Broadleaf signalgrass was absent at Keiser during both years.e Treatment means within a column can be compared using Fisher’s Protected LSD (a 5 0.05).f Symbols: (+), program more effective than standard at a 5 0.05; (2), program less effective than standard at a 5 0.05.g Clomazone plus quinclorac PRE fb propanil plus halosulfuron PREFLD was used as a standard herbicide program.


Stuttgart in 2010 because of reduced control of yellow nutsedgeplants with PRE application of imazosulfuron plus clomazone.Broadleaf signalgrass control at Stuttgart was $ 95% in bothyears, except in imazosulfuron plus clomazone EPOST fbquinclorac plus propanil PREFLD program in 2009.

Contrasts revealed that all imazosulfuron-containing pro-grams controlled barnyardgrass, broadleaf signalgrass, hempsesbania, and yellow nutsedge similar to or greater than thestandard program in at least one site-year (Table 3). Greater than91% control of hemp sesbania (at Keiser and Stuttgart),barnyardgrass (at Keiser in 2009 and at Stuttgart both years),yellow nutsedge (Keiser in 2010), and broadleaf signalgrass (bothyears at Stuttgart) with imazosulfuron in tank-mixture withclomazone, propanil, and quinclorac reveals that imazosulfurondoes not antagonize the efficacy of these herbicides.

Late-Season Weed Control. Hemp sesbania, yellow nutsedge,and broadleaf signalgrass control was $ 96% followingall herbicide programs in all site-years (data not shown).Data for barnyardgrass control are presented by site-yearsbecause of significant treatment-by-site-year interactions(Table 4). Barnyardgrass control at Keiser in 2010 andStuttgart both years was $ 90% in all herbicide programs.Because of greater early-season control, PRE fb EPOSTprograms and imazosulfuron plus clomazone EPOST fbthiobencarb plus propanil PREFLD program with imazosul-furon at 336 g ha21 controlled barnyardgrass greater than PREfb PREFLD programs at Keiser in 2009. Barnyardgrasscontrol with all imazosulfuron-containing programs wassimilar to or greater than the standard program at Keiser(both years) and Stuttgart in 2010.

Table 3. Hemp sesbania, barnyardgrass, yellow nutsedge, and broadleaf signalgrass control in rice at 2 WA PREFLD at Keiser and Stuttgart, AR during 2009and 2010.a–c


Control

Hemp sesbaniad Barnyardgrass Yellow nutsedge Broadleaf signalgrass

Keiser Stuttgart

Keiser Stuttgart Keiser Stuttgart Stuttgart

2009 2010 2009 2010 2010 2010 2009 2010

g ai ha21 ---------------------------------------------------------------------------------------------------------------% --------------------------------------------------------------------------------------------------------------


PRE 224 + 336 97 100 95 100 100 99 100 98 100 95EPOST 560 + 4,480


PRE 336 + 336 98 100 97 98 100 100 100 96 100 95EPOST 560 + 4480


EPOST 224 + 336 100 100 68 86 93 100 100 90 84 95PREFLD 560 + 4,480


EPOST 336 + 336 100 100 70 86 91 99 100 88 91 95PREFLD 560 + 4,480


EPOST 224 + 560 100 100 93 100 99 92 100 88 99 95PREFLD 3,360 + 3,360


EPOST 336 + 560 99 100 90 99 99 97 100 91 99 95PREFLD 3,360 + 3,360


PRE 224 + 336 96 100 51 100 99 98 100 58 99 95PREFLD 560 + 224


PRE 336 + 336 96 100 69 100 99 95 100 75 96 95PREFLD 560 + 336


PRE 224 + 336 100 100 69 91 97 99 100 90 96 95PREFLD 4,480 + 224


PRE 336 + 336 99 100 73 96 99 99 100 85 98 95PREFLD 4,480 + 336

Cloma + quinfb prop + halo

PRE 336 + 560 100 100 82 93 100 99 100 99 99 95PREFLD 4,480 + 53

LSD (0.05)e NS NS 22 4 2 NS NS 22 7 NS

Contrastsf

Standardg vs. PRE fb EPOST (2) NS NS (+) NS NS NS NS NS NSStandard vs. quin + prop PREFLD NS NS NS (2) (2) NS NS NS (2) NSStandard vs. thio + prop PREFLD NS NS NS (+) NS (2) NS NS NS NSStandard vs. quin + imaz PREFLD NS NS (2) (+) NS NS NS (2) NS NSStandard vs. prop + imaz PREFLD NS NS NS NS (2) NS NS NS NS NS

a Abbreviations: EPOST, early-POST; fb, followed by; PREFLD, preflooding; WA, weeks after; cloma, clomazone; halo, halosulfuron; imaz, imazosulfuron; NS, non-significant at a 5 0.05; prop, propanil; quin, quinclorac; thio, thiobencarb.


c Yellow nutsedge was absent at Keiser and Stuttgart during 2009. Broadleaf signalgrass was absent at Keiser during both years.d The treatment-by-year interaction was nonsignificant; therefore, data were pooled over years at Keiser and Stuttgart.e Treatment means within a column can be compared using Fisher’s Protected LSD (a 5 0.05).f Symbols: (+), program more effective than standard at a 5 0.05; (2), program less effective than standard at a 5 0.05.g Clomazone plus quinclorac PRE fb propanil plus halosulfuron PREFLD was used as a standard herbicide program.


Rice Injury and Yield. No injury to rice was observed with anyherbicide program in any site-year (data not shown). Treatment-by-site-year interactions were nonsignificant for rice yield. Thus,data were pooled across site-years (Table 4). Rice yield withall imazosulfuron-containing herbicide programs (6,630 to8,130 kg ha21 ) was similar to that of the standard program(7,240 kg ha21 ).

In summary, imazosulfuron EPOST or PREFLD at 224 or336 g ha21 controlled $ 93% hemp sesbania (except in 2009)and yellow nutsedge. Adequate rainfall or irrigation is required toachieve $ 90% yellow nutsedge control with PRE-appliedimazosulfuron. Imazosulfuron plus clomazone PRE fb quin-clorac plus propanil EPOST and imazosulfuron plus quincloracEPOST fb thiobencarb plus propanil PREFLD controlled weedsmore consistently than all other herbicide programs and providedweed control greater or similar to the standard herbi-cide program. With all imazosulfuron-containing programs,

late-season control of barnyardgrass (except at Keiser in 2009),hemp sesbania, broadleaf signalgrass, and yellow nutsedge was$ 90% in all site-years. Addition of imazosulfuron to rice weedmanagement programs will increase the choice of herbicides formid-South rice producers. Although there was no indication ofantagonism between imazosulfuron and other tank-mixedherbicides in the present study, future studies are needed tofully evaluate possible interactions. This will help improve early-season weed control efficacy of imazosulfuron and potential tank-mix partners.

Sources of Materials1 Roundup PowerMaxTM, Monsanto Co., 800 N. Lindbergh

Blvd. St. Louis, MO 63167.2 V-10142 experimental compound, Valent U.S.A. Corporation,

Walnut Creek, CA 94596.

Table 4. Rice yield (pooled over site-years) and late-season (6 WA PREFLD) barnyardgrass control in rice at Keiser and Stuttgart during 2009 and 2010.a–c


Control

Yield

Barnyardgrass

Keiser Stuttgart

2009 2010 2009 2010

g ai ha21 --------------------------------------------------------------------% ------------------------------------------------------------------- kg ha21


PRE fb EPOST 224 + 336 fb 560 + 4,480 88 99 100 100 8,030


PRE fb EPOST 336 + 336 fb 560 + 4,480 89 99 100 100 8,130


EPOST fb PREFLD 224 + 336 fb 560 + 4,480 79 92 95 100 7,460






EPOST fb PREFLD 336 + 560 fb 3,360 + 3,360 90 99 97 96 7,430


PRE fb PREFLD 224 + 336 fb 560 + 224 63 99 100 95 7,870


PRE fb PREFLD 336 + 336 fb 560 + 336 59 100 99 98 7,150


PRE fb PREFLD 224 + 336 fb 4,480 + 224 64 92 92 96 6,630


PRE fb PREFLD 336 + 336 fb 4,480 + 336 60 96 98 93 7,630

Cloma + quin fbprop + halo

PRE fb PREFLD 336 + 560 fb 4,480 + 53 73 91 100 98 7,240

LSD (0.05)d 22 6 6 NS NS

Contrastse

Standardf vs. PRE fb EPOST NS (+) NS NS NSStandard vs. quin + prop PREFLD NS NS (2) NS NSStandard vs. thio + prop PREFLD NS (+) (2) NS NSStandard vs. quin + imaz PREFLD NS (+) NS NS NSStandard vs. prop + imaz PREFLD NS NS (2) NS NS

a Abbreviations: EPOST, early-POST; fb, followed by; PREFLD, preflooding; WA, weeks after; cloma, clomazone; halo, halosulfuron; imaz, imazosulfuron; NS, non-significant at a 5 0.05; prop, propanil; quin, quinclorac; thio, thiobencarb.


c Late-season evaluations at Stuttgart in 2010 were made at 10 WA PREFLD.d Treatment means within a column can be compared using Fisher’s Protected LSD (a 5 0.05).e Symbols: (+), program more effective than standard at a 5 0.05; (2), program less effective than standard at a 5 0.05.f Clomazone plus quinclorac PRE fb propanil plus halosulfuron PREFLD was used as a standard herbicide program.


3 Dyne-A-Pak, Helena Chemical Co., 225 Schilling Boulevard,Suite 300, Collierville, TN 38017.

4 110015XR flat-fan spray nozzles, Teejet Technologies, 1801Business Park Drive, Springfield, IL 62703.

5 SAS software for Windows, Version 9.1.3. SAS Institute Inc.,100 SAS Campus Dr., Cary, NC 27513.

6 CommandH 3 ME, FMC Corporation, Agricultural ProductsGroup, 1735 Market Street, Philadelphia, PA 19103.

7 Facet 75 DF, BASF Corporation, P.O. Box 13528, ResearchTriangle Park, NC 27709.

8 Stam M-4, Dow AgroSciences LLC, 9330 Zionsville Road,Indianapolis, IN 46258.

9 Bolero 8.0 EC, Valent U.S.A. Corporation, P.O. Box 8025.Walnut Creek, CA 94596.

10 PermitTM, Gowan Company LLC, 370 Main Street, Yuma,AZ 85364.

Acknowledgments

This research was supported by the Valent Corporation andArkansas Rice Research and Promotion Board.

Literature Cited

Ahmadi, M. S., L. C. Haderlie, and G. A. Wicks. 1980. Effect of growth stageand water stress on barnyardgrass (Echinochloa crus-galli) control and onglyphosate absorption and translocation. Weed Sci. 28:277–282.

Avila, L. A., S. A. Senseman, G. N. McCauley, J. M. Chandler, and J. H. O’-Barr.2005. Effect of flood timing on red rice (Oryza spp.) control with imazethapyrapplied at different dry-seeded rice growth stages. Weed Technol. 19:476–480.

Baron, J. 2006. The IR-4 Project: 2006 IR-4 New Products/Transitional SolutionList. http://www.aftresearch.org/sai/public/pdf/NewProductsAugust2006.pdf.Accessed: April 5, 2011.

[CDMS] Crop Data Management Systems, Inc. 2011. CommandH 3ME. http://www.cdms.net/LDat/ld3U6001.pdf. Accessed: April 15, 2011.

Crawford, S. H. and D. L. Jordan. 1995. Comparison of single and multipleapplications of propanil and residual herbicides in dry-seeded rice (Oryzasativa). Weed Technol. 9:153–157.

Felix, J. and R. A. Boydston. 2010. Evaluation of imazosulfuron for yellownutsedge (Cyperus esculentus) and broadleaf weed control in potato. WeedTechnol. 24:471–477.

Godara, R. K. 2010. Texasweed [Caperonia palustris (L.) St. Hil.] interference andmanagement in drill-seeded rice. Ph.D dissertation. Baton Rouge, LA:Louisiana State University. Pp. 105–108.

Henry, G. M. and B. S. Sladek. 2008. Control of yellow and purple nutsedge inbermudagrass turf with V-10142. Proc. South. Weed Sci. Soc. 61:125.

Jordan, D. L. 1997. Efficacy of reduced rates of quinclorac applied with propanil orpropanil plus molinate in dry-seeded rice (Oryza sativa). Weed Sci. 45:824–828.

Jordan, D. L., D. K. Miller, and S. H. Crawford. 1998. Barnyardgrass(Echinochloa crus-galli) control in dry-seeded rice (Oryza sativa) with soilapplied and postemergence herbicide programs. Weed Technol. 12:69–73.

Kirksey, K. B., R. M. Hayes, W. A. Charger, C. A. Mullions, and T. C. Mueller.1996. Clomazone dissipation in two Tennessee soils. Weed Sci. 44:959–963.

Kwon, S. L., R. J. Smith, Jr., and R. E. Talbert. 1991. Interference duration ofred rice (Oryza sativa) in rice (O. sativa). Weed Sci. 39:363–368.

Masson, J. A., E. P. Webster, and B. J. Williams. 2001. Flood depth, applicationtiming, and imazethapyr activity in imidazolinone-tolerant rice (Oryza sativa).Weed Technol. 15:315–319.

McGregor, J. T., Jr., R. J. Smith, Jr., and R. E. Talbert. 1988. Interspecific andintraspecific interference of broadleaf signalgrass (Brachiaria platyphylla) in rice(Oryza sativa). Weed Sci. 36:589–593.

Mills, J. A. and W. W. Witt. 1989. Efficacy, phytotoxicity, and persistence ofimazaquin, imazethapyr, and clomazone in no-till double-crop soybeans(Glycine max). Weed Sci. 37:353–359.

Morrica, P., F. Barbato, R. Dello-Iacovo, S. Seccia, and F. Ungaro. 2001a.Kinetics and mechanism of imazosulfuron hydrolysis. J. Agric. Food Chem.49:3816–3820.

Morrica, P., F. Barbato, A. Giordano, S. Seccia, and F. Ungaro. 2000. Adsorptionand desorption of imazosulfuron by soil. J. Agric. Food Chem. 48:6132–6137.

Morrica, P., A. Giordano, S. Seccia, F. Ungaro, and M. Ventriglia. 2001b.Degradation of imazosulfuron in soil. Pest Manag. Sci. 57:360–365.

Norsworthy, J. K., N. R. Burgos, R. C. Scott, and K. L. Smith. 2007. Consultantperspectives on weed management needs in Arkansas rice. Weed Technol.21:832–839.

Norsworthy, J. K., S. K. Bangarwa, R. C. Scott, J. Still, and G. M. Griffith. 2010.Use of propanil and quinclorac tank mixtures for broadleaf weed control onrice (Oryza sativa) levees. Crop Protect. 29:255–259.

Norsworthy, J. K., S. S. Rana, J. Mattice, D. B. Johnson, J. Wilson, and R. C.Scott. 2011. Use of imazosulfuron in Arkansas rice. Pages 160–166 in R. J.Norman and K.A.K. Moldenhauer, eds. B. R. Wells Rice Research Studies2010. Arkansas Agricultural Experiment Station Research Series 591.

Payne, S. A. and L. R. Oliver. 2000. Weed control programs in drilledglyphosate-resistant soybean. Weed Technol. 14:413–422.

Slaton, N. and R. Cartwright. 2010. Rice stand establishment. Pages 21–28 inN. A. Slaton, ed. Rice Production Handbook. Little Rock, AR: ArkansasCooperative Extension Service, University of Arkansas, Pub. MP-192.

Smith, R. J., Jr. 1968. Weed competition in rice. Weed Sci. 16:252–255.Smith, R. J., Jr. 1974. Competition of barnyardgrass with rice cultivars. Weed Sci.

22:423–426.Smith, R. J., Jr. 1981. Control of red rice (Oryza sativa) in water-seeded rice (O.

sativa). Weed Sci. 39:663–666.Smith, R. J., Jr. 1988. Weed thresholds in southern U.S. rice (Oryza sativa). Weed

Technol. 2:232–241.Smith, R. J., Jr. and W. T. Fox. 1973. Soil water and growth of rice and weeds.

Weed Sci. 21:61–63.Smith, R. J., Jr. and J. E. Hill. 1990. Weed control technology in U.S. rice.

Pages 314–327 in B. T. Grayson, M. B. Green and L. D. Coping, eds. PestManagement in Rice. London: Elsevier.

Tacker, P., E. Vories, C. Wilson, Jr., and N. Slaton. 2010. Water management.Pages 75–86 in N. A. Slaton, ed. Rice Production Handbook. Little Rock,AR: Arkansas Cooperative Extension Service, University of Arkansas, Pub.MP-192.

Usui, K. 2001. Metabolism and selectivity of rice herbicides in plants. Weed Biol.Manag. 1:137–146.

Zhang, W., E. P. Webster, K. J. Pellerin, and D. C. Blouin. 2006. Weed controlprograms in drill-seeded imidazolinone-resistant rice (Oryza sativa). WeedTechnol. 20:956–960.

Received May 2, 2011, and approved June 28, 2011.


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Use of Imazosulfuron in Herbicide Programs for Drill-Seeded Rice (Oryza sativa) in the Mid-South United States