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Crop Protection 31 (2012) 45e49

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Crop Protection

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Weed control and sensitivity of oats (Avena sativa) with various dosesof saflufenacil

Nader Soltani*, Christy Shropshire, Peter H. SikkemaUniversity of Guelph Ridgetown Campus, 120 Main Street East, Ridgetown, Ontario, Canada N0P 2C0

a r t i c l e i n f o

Article history:Received 13 April 2011Received in revised form25 August 2011Accepted 26 August 2011

Keywords:DensityDry weightDose responseHerbicide sensitivityOats (Avena sativa L.)ToleranceYield

* Corresponding author. Tel.: þ1 519 6751221; fax:E-mail address: nsoltani@ridgetownc.uoguelph.ca

0261-2194/$ e see front matter � 2011 Elsevier Ltd.doi:10.1016/j.cropro.2011.08.016

a b s t r a c t

Saflufenacil is a new herbicide being developed by BASF for broadleaved weed control in maize, soybeanand other crops prior to crop emergence. Six field studies were conducted in Ontario, Canada over a threeyear period (2008e2010) to evaluate the potential of saflufenacil applied pre-emergence (PRE) at variousdoses for broadleaved weed control in oats. Saflufenacil applied PRE caused minimal visible injury at 1, 2and 4 weeks after emergence (WAE) in oats. At 4 WAE, the dose of saflufenacil required to provide 95%control of Ambrosia artemisiifolia (common ragweed), Chenopodium album (common lambsquarters),Polygonum convolvulus (wild buckwheat), Polygonum scabrum (green smartweed) and Sinapsis arvensis(wild mustard) was 72 to >100, >100, 74, 58 and >100 g ai ha�1, respectively. Generally, similar saflu-fenacil dose-response trends were seen at 8 WAE. The doses of saflufenacil required to provide 95%reduction in density and dry weight ranged from 95 to >100 and 42 to >100 g ai ha�1 respectively for A.artemisiifolia, C. album, P. convolvulus, P. scabrum and S. arvensis. Oat yield showed no sensitivity tosaflufenacil at the doses evaluated. Based on this study, saflufenacil applied PRE can be safely used inspring planted oats for the control of some troublesome annual broadleaved weeds.

� 2011 Elsevier Ltd. All rights reserved.

1. Introduction

Oats (Avena sativa) are an important spring cereal grown inOntario. In 2009, growers in Ontario seeded 34,000 ha andproduced nearly 80,000 tonnes of oats with a farm gate value ofapproximately $15,000,000 (McGee, 2011). Weed management isa critical component in successful oat production (Sikkema et al.,2008). Substantial crop yield and associated economic losses canoccur if weeds are not adequately controlled. Efficacious pre-emergence (PRE) applied residual broadleaved herbicides with anadequate margin of crop safety that can be tankmixed withglyphosate would allow no-till oat producers to combine twoweedcontrol operations in one pass, burndown of emerged weeds priorto seeding and full season residual broadleaf weed control. Thiswould be an additional crop production tactic that would help oatgrowers to be more competitive in the marketplace.

Herbicides available for oats in Ontario have not changed muchin recent years (OMAFRA, 2010; Sikkema et al., 2008; Soltani et al.,2006). There have been reports of crop sensitivity in cereals withsome of these herbicides (Sikkema et al., 2007). There are currentlyno soil applied residual herbicides available for broadleaved weed

þ1 519 674 1600.(N. Soltani).

All rights reserved.

control in oats in Ontario. Availability of new residual herbicidesthat provide selective and consistent control of annual broadleavedweeds will enable Ontario oat growers to improve their competi-tive edge in the marketplace. More research is needed to determinethe efficacy of newly developed herbicides with a novel mode ofaction in oats.

Saflufenacil is a new herbicide being developed for pre-plantburndown and residual broadleaved weed control prior to cropemergence in maize, soybean, sorghum, wheat and other crops(Soltani et al., 2009). Saflufenacil can control troublesome broad-leaved weeds including Abutilon theophrasti (velvetleaf), Ambrosiaartemisiifolia (common ragweed), Xanthium strumarium (commoncocklebur), Polygonum persicaria (ladysthumb), Amaranthus retro-flexus (redroot pigweed), Amaranthus tuberculatus var. rudis(common waterhemp) and Chenopodium album (common lambs-quarters) including Group 2, 5 and 9 herbicide resistant biotypes(Anonymous, 2008; Liebl et al., 2008). Saflufenacil is a pyr-imidinedione chemical compound that inhibits protoporphy-rinogen-IX-oxidase (PPO). Saflufenacil has both contact andresidual activity against susceptible weeds which show injurysymptomswithin a fewhours anddie in 1e3days (Liebl et al., 2008).Saflufenacil is mainly translocated in the xylem and has limitedmobility in the phloem (Liebl et al., 2008). Saflufenacil is applied atrelatively low doses and has low environmental, toxicological and

N. Soltani et al. / Crop Protection 31 (2012) 45e4946

eco-toxicological impact with minimal residual carryover andpersistence in the soil (Anonymous, 2008).

The few studies published on saflufenacil weed control efficacyhave shown very good control of some broadleaved weeds (Frihaufet al., 2010a, 2010b; Geier et al., 2009; Knezevic et al., 2009a).Saflufenacil applied PRE in cereals has been shown to causeminimal crop injury in winter wheat (Triticum aestivum), springbarley (Hordeum vulgare), oats and wheat (Knezevic et al., 2010;Sikkema et al., 2008). There is little information on the efficacy ofsaflufenacil at various doses for the control of broadleaf weeds inoats. Saflufenacil has the potential to provide oat growers inOntario with an additional herbicide mode of action option toeffectively manage troublesome broadleaved weeds. The proposedsaflufenacil use dose for oats in Ontario is 25 g ai ha�1. The objectiveof this research was to evaluate the potential of saflufenacil appliedPRE at 6.25e100 g ai ha�1 for broadleaved weed control in springoats.

2. Materials and methods

Six field studies were conducted at the Huron Research Station,Exeter, Ontario over a three year period (2008e2010). The soil forstudy sites was a Brookston clay loam with 38% sand, 41% silt, 21%clay, 3.7% OM and pH of 7.8 in 2008; 39% sand, 33% silt, 28% clay,4.7% OM and pH of 7.9 in 2009; and 32% sand, 42% silt, 26% clay,3.7% OM and pH of 7.8 in 2010. Seedbed preparation consisted ofmoldboard plowing in the autumn followed by two passes witha cultivator with a rolling basket harrows in the spring.

The experimental designwas a randomized complete block withfour replications. Therewere nine treatments that included aweedycontrol, weed-free control, bromoxynil/MCPA at 560 g ai ha�1 (thestandard treatment) applied early post-emergence (POST) andsaflufenacil applied pre-emergence (PRE) at 6.25, 12.5, 25, 50, 75and 100 g ai ha�1. Plots were 2 m wide by 10 m long. Spring oats‘Sherwood’ was seeded with a double disc drill at 130 kg ha�1 inrows 17.5 cm apart at a depth of 4 cm on April 17 and 21 in 2008,April 16 and 25 in 2009, and April 3 and 5 in 2010.

Treatments were applied PRE within 3 days after planting (DAP)with a CO2 pressurized backpack sprayer calibrated to deliver200 L ha�1 at 241 kPa. The boomwas 1.5 m long with four ultra lowdrift nozzles (ULD120-02, Hypro, New Brighton, MN) spaced 50 cmapart. All plots including the non-treated control were kept weed-free as required.

Estimates of crop injury were rated visually at 1, 2 and 4 weekafter emergence (WAE) and weed control was rated at 4 and 8WAEon a scale of 0e100% (0 ¼ no visible injury/weed control and100 ¼ plant death/no weed control). At 8 WAE, a random 1 mquadrat section of each plot was selected, naturally occurringweeds within the quadrat were counted by species to determinepopulation density and were cut at the soil surface, bagged byspecies for each plot and dried to constant moisture at 60 �C todetermine shoot dry weight. Oats were harvested on July 29, 2008,July 8, 2009 and July 22, 2010 using a plot combine. Yields wereadjusted to 13.5% moisture.

2.1. Statistical analysis

Data were analyzed using non-linear regression (PROC NLIN) inSAS (2008). When doseeresponse did not fit the data, a segmentedlinear regression was used. The weedy and weed-free checks andthe bromoxynil/MCPA treatment were not included in regressionanalysis. Weed density and dry weight were converted to a percentof the weedy check and yield was converted to a percent of theweed-free check prior to analysis. The PROC MIXED procedure ofSAS (2008) was used to determine which environments

(comprising sites and years) could be combined for regressionanalysis (only if the environment by dose interaction was notsignificant).

2.1.1. Regression equations (models) usedAll parameters were regressed against saflufenacil dose, desig-

nated as DOSE in the equations.The equations used for percent injury of oats (segmented linear)

were as follows:

YL ¼ a0þ b1�DOSE [1a]

YR ¼ a0þ b1�jþ br1�ðDOSE� jÞ [1b]

where YL and YR are the left and right segments, respectively, a0 isthe left intercept, b1 is the slope of the left segment, br1 is the slopeof the right segment and j is the junction point of the two segments.

The equation used for percent weed control (doseeresponse),using a four parameter log-logistic model was:

Y ¼ C þ ðD� CÞ=ð1þ exp ½ � bðln DOSE � ln I50Þ�Þ [2]

where C is the lower asymptote, D is the upper asymptote, b is theslope and I50 is the dose which gives a response halfway between Cand D (in one case, doseeresponse did not fit the data (SINAR forenvironment 1, 4 WAE), and a segmented linear regression Eq. (1)was used instead).

The equation used for percent density and dry weight (doseeresponse), using a four parameter log-logistic model was:

Y ¼ C þ ðD� CÞ=ð1þ exp ½bðln DOSE� ln I50Þ�Þ [3]

where parameters are identical to Eq.(2), the only difference is thatb is positive to reflect the change in direction of the response.

The equation used for yield (exponential to maximum) was:

Y ¼ f þ g�ð1� exp ½�h � DOSE�Þ [4]

where f is the intercept, g is the magnitude of the response and h isthe rate (slope) of the response.

2.1.2. Predicted valuesRegression equations were used to calculate predicted saflufe-

nacil doses (g ai ha�1) that resulted in 5 and 10% crop injury (R5,R10), or the doses required to achieve 50 and 95% control of weedspecies or a 50 and 95% reduction in percent weed density or dryweight (R50 and R95), or the dose which provided 90, 95 and 98%yield of the weed-free check (R90, R95, R98). If any dose was pre-dicted to be higher than 100 g ai ha�1, it was simply expressed as“>100” since it would be improper to extrapolate outside the rangeof doses evaluated in these experiments.

3. Results and discussion

3.1. Visible injury

At 1 WAE, visible injury in all environments was zero (data forvisible injury are not presented). At 2WAE, only environment 2 (thesecond site in 2008) had non-zero injury and could not becombined with the other environments having zero injury. The R5

(dose causing 5% injury) was 64 g ai ha�1 of saflufenacil and R10(dose causing 10% injury) was 87 g ai ha�1. At 4WAE, environments2, 5 and 6 (the second site in 2008 and both 2010 sites) were non-zero and could not be combined with other the environments thathad zero injury. The R5 and R10 were both >100 g ai ha�1.

In other studies, saflufenacil applied PRE has been shown tocause little injury in wheat at doses up to 400 g ai ha�1 and in

Table 1Regression parameter estimates and predicted saflufenacil doses from doseeresponse and segmented linear models of visual weed control at 4 WAE.a

Weed WAE Envd Parameter estimatesb (�SE) Predicted saflufenacil dosec

C D b I50 R50 R95

% g ai/ha

Dose responseAMBEL 4 3 �2.7 � 10�11(0.0) 61 (9) 3.0 (1.9) 26 (6) 44 >100AMBEL 4 1, 2, 4e6 2.1 (4.8) 100 (0) 2.3 (0.4) 21 (2) 20 72CHEAL 4 1e6 4.1 � 10�2(2.6) 97 (4) 2.7 (0.5) 28 (2) 28 >100POLCO 4 1, 2, 5, 6 0.0 (0.0) 100 (0) 2.1 (0.4) 18 (2) 18 74POLSC 4 1e4 0.0 (0.0) 100 (0) 1.8 (0.4) 11 (1) 11 58SINAR 4 2e6 1.4 � 10�1(3.2) 95 (4) 1.8 (0.3) 16 (1) 17 >100Segmented linear a0 b1 br1 jSINAR 4 1 1.4 � 10�15(8.5) �2.3 � 10�16 (1.0) 0.77 (0.17) 18 (21) 83 >100

a Abbreviations: AMBEL, common ragweed; CHEAL, common lambsquarters; Env, environment; POLCO, wild buckwheat; POLSC, green smartweed; SINAR, wild mustard;WAE, weeks after oat emergence.

b Dose response parameters (Eq. (2)): b, slope; C, lower asymptote; D, upper asymptote; I50, dose required for 50% response. Segmented linear parameters (Eq. (1a) and(1b)): a0, left intercept; b1, slope of left segment; br1, slope of right segment; j, junction of left and right segments.

c R50 and R95 are the doses required to give a reduction in percent weed dry weight of 50 and 95%, respectively, for a given weed species.d Environments: 1, 2008a; 2, 2008b; 3, 2009a; 4, 2009b; 5, 2010a; 6, 2010b.

N. Soltani et al. / Crop Protection 31 (2012) 45e49 47

spring planted barley at doses up to 100 g ai ha�1 (Knezevic et al.,2010; Sikkema et al., 2008; Jenks et al., 2008). The minimal injuryseen with saflufenacil applied PRE in oats in this study is alsosimilar to those found with currently used POST herbicides inOntario such as 2,4-D, bromoxynil plus MCPA and dichlorprop plus2,4-D (Sikkema et al., 2007, 2008; Soltani et al., 2006). However,other studies have seen significant injury with POST appliedherbicides such as dicamba, dicamba plus MCPA plus mecopropand dicamba plus 2,4-D in winter wheat (Schroeder and Banks,1989; Sikkema et al., 2007; Tottman, 1977).

3.2. Percent weed control, density and dry weight

3.2.1. Ambrosia artemisiifoliaAt 4 WAE, the doses of saflufenacil required to provide 50% and

95% control of A. artemisiifolia ranged from 20 to 44 and 72 to>100 g ai ha�1, respectively (Table 1). At 8 WAE, the doses ofsaflufenacil required to provide 50% and 95% control of A. artemi-siifolia were 18e52 and 44e>100 g ai ha�1, respectively (Table 2).Weed population density and dry weight of A. artemisiifolia showedthe same general trend as the visible control. The doses of saflu-fenacil required to provide 50% and 95% reduction in percent A.artemisiifolia density were 13 and >100 g ai ha�1, respectively(Table 3). The doses of saflufenacil required to provide 50% and 95%reduction in percent A. artemisiifolia dry weight were 12 and88 g ai ha�1, respectively (Table 4).

Table 2Regression parameter estimates and predicted saflufenacil doses from doseeresponse m

Weed Envd Parameter estimatesb (�SE)

C D

%

AMBEL 3 �4.5 � 10�12 (0.0) 100 (0)AMBEL 1, 2, 4e6 2.7 � 10�2 (3.1) 100 (0)CHEAL 5 0.0 (0.0) 99 (4)CHEAL 1e3, 4, 6 0.0 (0.0) 99 (4)POLCO 1, 2, 5, 6 2.7 (4.4) 100 (0)POLSC 1e4 2.0 (7.1) 100 (0)SINAR 1e6 0.0 (0.0) 100 (0)

a Abbreviations: AMBEL, common ragweed; CHEAL, common lambsquarters; Env, envWAE, weeks after oat emergence.

b Dose response parameters (Eq. (2)): b, slope; C, lower asymptote; D, upper asymptoc R50 and R95 are the doses required to give a reduction in percent weed dry weight ofd Environments: 1, 2008a; 2, 2008b; 3, 2009a; 4, 2009b; 5, 2010a; 6, 2010b.

3.2.2. C. albumAt 4 WAE, the doses of saflufenacil required to provide 50% and

95% control of C. album were 28 and >100 g ai ha�1, respectively(Table 1). At 8 WAE, the doses of saflufenacil required to provide50% and 95% control of C. album were 8e23 and 15e98 g ai ha�1,respectively (Table 2). Weed density and dry weight of C. albumresponded similarly to the visible control. The doses of saflufenacilrequired to provide 50% and 95% reduction in percent C. albumdensity were 17 and >100 g ai ha�1, respectively (Table 3). Thedoses of saflufenacil required to provide 50% and 95% reduction inpercent C. album dry weight were 12 and >100 g ai ha�1, respec-tively (Table 4).

3.2.3. Polygonum convolvulusAt 4 WAE, the doses of saflufenacil required to provide 50% and

95% control of P. convolvulus were 18 and 74 g ai ha�1, respectively(Table 1). At 8 WAE, responses were similar to 4 WAE. The doses ofsaflufenacil required to provide 50% and 95% control of P. convol-vulus were 25 and 71 g ai ha�1, respectively (Table 2). Weed pop-ulation density and dry weight of P. convolvulus showed the samegeneral trend as the visible control. The doses of saflufenacilrequired to provide 50% and 95% reduction in percent P. convolvulusdensity were 18 and 95 g ai ha�1, respectively (Table 3). The doses ofsaflufenacil required to provide 50% and 95% reduction in percent P.convolvulus dry weight were 13 and 71 g ai ha�1, respectively(Table 4). In other studies Convolvulus arvensis was controlled with

odels of visual weed control at 8 WAE.a

Predicted saflufenacil dosec

b I50 R50 R95

g ai/ha

2.2 (0.3) 52 (3) 52 >1003.2 (0.4) 18 (1) 18 445.1 (1.7) 8 (1) 8 152.2 (0.3) 22 (2) 23 982.8 (0.5) 25 (2) 25 711.8 (0.4) 17 (3) 17 841.6 (0.1) 20 (1) 20 >100

ironment; POLCO, wild buckwheat; POLSC, green smartweed; SINAR, wild mustard;

te; I50, dose required for 50% response.50 and 95%, respectively, for a given weed species.

Table 3Regression parameter estimates and predicted saflufenacil doses from doseeresponse models of percent weed density at 8 WAE.a

Weed Envd Parameter estimatesb (�SE) Predicted saflufenacil dosec

C D b I50 R50 R95

% g ai/ha

AMBEL 1e6 3.3 (6.7) 100 (6) 1.7 (0.5) 12 (2) 13 >100CHEAL 1e6 �6.2 � 10�12 (0.0) 98 (7) 1.2 (0.2) 18 (4) 17 >100POLCO 1, 2 �7.3 � 10�12 (0.0) 97 (12) 1.8 (0.7) 19 (5) 18 95POLSC 2, 4 �4.3 � 10�12 (0.0) 97 (14) 1.2 (0.5) 11 (5) 11 >100SINAR 1e6 6.1 (8.3) 100 (9) 1.9 (0.7) 13 (3) 14 >100

a Abbreviations: AMBEL, common ragweed; CHEAL, common lambsquarters; Env, environment; POLCO, wild buckwheat; POLSC, green smartweed; SINAR, wild mustard;WAE, weeks after oat emergence.

b Dose response parameters (Eq. (3)): b, slope; C, lower asymptote; D, upper asymptote; I50, dose required for 50% response.c R50 and R95 are the doses required to give a reduction in percent weed dry weight of 50 and 95%, respectively, for a given weed species.d Environments: 1, 2008a; 2, 2008b; 3, 2009a; 4, 2009b; 5, 2010a; 6, 2010b.

N. Soltani et al. / Crop Protection 31 (2012) 45e4948

saflufenacil applied at 7e71 g ai ha�1 in Nebraska (Knezevic et al.,2009a,b, 2010).

3.2.4. Polygonum scabrumAt 4 WAE, the doses of saflufenacil required to provide 50% and

95% control of P. scabrum were 11 and 58 g ai ha�1, respectively(Table 1). At 8 WAE, the doses of saflufenacil required to provide50% and 95% control of P. scabrum were 17 and 84 g ai ha�1,respectively (Table 2). Density and dry weight of P. scabrumresponded similarly to the visible control. The doses of saflufenacilrequired to provide 50% and 95% reduction in percent P. scabrumdensity were 11 and >100 g ai ha�1, respectively (Table 3). Thedoses of saflufenacil required to provide 50% and 95% reduction inpercent P. scabrum dry weight were 6 and >100 g ai ha�1, respec-tively (Table 4).

3.2.5. Sinapsis arvensisAt 4 WAE, the doses of saflufenacil required to provide 50% and

95% control of S. arvensis were 17e83 and >100 g ai ha�1, respec-tively (Table 1). At 8 WAE, the doses of saflufenacil required toprovide 50% and 95% control of S. arvensis were 20 and>100 g ai ha�1, respectively (Table 2). Density and dry weight of S.arvensis responded similarly to the visible control. The doses ofsaflufenacil required to provide 50% and 95% reduction in percent S.arvensis density were 14 and >100 g ai ha�1, respectively (Table 3).The doses of saflufenacil required to provide 50% and 95% reductionin percent S. arvensis dry weight were 8 and 42 g ai ha�1, respec-tively (Table 4).

In other studies, Knezevic et al. (2009a) reported that thesaflufenacil applied at 103 g ai ha�1 provided 90% dry weightreduction of Thlaspi arvense. Geier et al. (2009) found 82e98%reduction in dry weight and 77e98% reduction in density of

Table 4Regression parameter estimates and predicted saflufenacil doses from doseeresponse m

Weed Envd Parameter estimatesb (�SE)

C D

%

AMBEL 1e6 2.5 (6.4) 101 (7)CHEAL 1e6 5.6 (11.1) 100 (6)POLCO 1, 2 1.5 (11.7) 102 (12)POLSC 2, 4 5.6 (18.7) 100 (12)SINAR 1e6 �2.5 � 10�11 (0.0) 100 (7)

a Abbreviations: AMBEL, common ragweed; CHEAL, common lambsquarters; Env, envWAE, weeks after oat emergence.

b Dose response parameters (Eq. (3)): b, slope; C, lower asymptote; D, upper asymptoc R50 and R95 are the doses required to give a reduction in percent weed dry weight ofd Environments: 1, 2008a; 2, 2008b; 3, 2009a; 4, 2009b; 5, 2010a; 6, 2010b. 11.

Chorispora tenella, Descurainia sophia, Amaranthus palmeri, A.retroflexus, and Amaranthus albus (averaged across species) withsaflufenacil applied at 6e30 g ai ha�1. Knezevic et al. (2009a) alsoreported that the dose of saflufenacil required for providing 90%dry weight reduction of Taraxacum officinale was 93 g ai ha�1.

3.3. Yield

Oats yield showed no sensitivity to saflufenacil at the dosesevaluated. Even in theweedy check (dose¼ 0), mean crop yield wasgreater than 90% of the weed-free check, so the values for R90, R95and R98 were 0, 1 and 4 g ai ha�1, respectively (data not shown).Knezevic et al. (2010) found no effect on yield of winter wheat withsaflufenacil applied PRE at doses as high 400 g ai ha�1 which is 16times the proposed registration dose of 25 g ai ha�1. Frihauf et al.(2010b) also found no adverse yield effect with saflufenacil aloneup to 50 g ai ha�1 or tankmixed with 2,4-D in winter wheat.Saflufenacil applied PRE at doses up to 100 g ai ha�1 had no adverseeffect on yield of spring planted barley and wheat (Sikkema et al.,2008). Yield responses with saflufenacil are similar to the yieldresponses of other cereals with currently used POST herbicides inOntario such as 2,4-D amine, bromoxynil plus MCPA and dichlor-prop plus 2,4-D (Sikkema et al., 2007). However, other studies haveshown yield reduction of 12e39% with dicamba alone, or incombination with a phenoxy herbicide (Martin et al., 1989). Ivanyet al. (1990), Rinella et al. (2001) and Tottman (1982) also foundsignificant yield losses in cereals with herbicides such as dicamba,while Tottman (1978) found reduced yields with tankmixes con-taining dicamba, 2,3,6-TBA, MCPA or mecoprop applied POST towinter wheat.

odel of percent weed dry weight at 8 WAE.a

Predicted saflufenacil dosec

b I50 R50 R95

g ai/ha

1.8 (0.5) 12 (2) 12 881.3 (0.5) 11 (3) 12 >1002.0 (1.0) 13 (4) 13 711.1 (1.2) 6 (3) 6 >1001.8 (0.4) 8 (1) 8 42

ironment; POLCO, wild buckwheat; POLSC, green smartweed; SINAR, wild mustard;

te; I50, dose required for 50% response.50 and 95%, respectively, for a given weed species.

N. Soltani et al. / Crop Protection 31 (2012) 45e49 49

4. Conclusions

Based on this study, saflufenacil applied PRE can be safely usedin spring planted oats for the control of some troublesome weeds.The doses of saflufenacil required to adequately control A. artemi-siifolia, C. album and S. arvensiswere higher than the doses requiredto control P. convolvulus and P. scabrum. The registration of saflu-fenacil would provide Ontario oat growers with an additional novelherbicide mode of action for the control of troublesome broad-leaved weeds. In addition, since saflufenacil can be tankmixed withglyphosate it would allow oat growers to combine their pre-plantburndown and PRE residual broadleaf weed control operations inone pass across the field. These results are consistent with theproposed PRE use pattern for saflufenacil.

Acknowledgements

The authors acknowledge Todd Cowan for his expertise andtechnical assistance in these studies. Funding for this project wasprovided in part by the Grain Farmers of Ontario (GFO).

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