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Crop Protection 27 (2008) 1495–1497

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Crop Protection

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Tolerance of spring barley (Hordeum vulgare L.), oats (Avena sativa L.)and wheat (Triticum aestivum L.) to saflufenacil

Peter H. Sikkema, Christy Shropshire, Nader Soltani*

University 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 19 February 2008Received in revised form 7 July 2008Accepted 10 July 2008

Keywords:BarleyHeightHerbicide sensitivityOatsToleranceYieldWheat

* Corresponding author. Tel.: þ1 519 674 1645; fax:E-mail address: nsoltani@ridgetownc.uoguelph.ca

0261-2194/$ – see front matter � 2008 Elsevier Ltd.doi:10.1016/j.cropro.2008.07.009

a b s t r a c t

Saflufenacil is a new herbicide being developed by BASF for pre-emergence application for broadleavedweed control in maize and other crops. Three field studies were conducted in Ontario, Canada overa 2-year period (2006 and 2007) to evaluate the tolerance of spring cereals (barley, oats, and wheat) topre-emergence and post-emergence applications of saflufenacil at 50 and 100 g ai ha�1. Saflufenacil pre-emergence caused minimal visible injury (1% or less) at 3, 7, 14 and 28 days after emergence and had noadverse effect on plant height or yield of barley, oats, and wheat. Saflufenacil plus the surfactant Merge(1% v/v) applied post-emergence caused as much as 76, 60, 52 and 35% visible injury in spring cereals at3, 7, 14 and 28 DAT, respectively. Injury with saflufenacil plus Merge applied post-emergence decreasedover time and was generally greater as dose increased. Saflufenacil plus Merge applied post-emergencereduced plant height by as much as 16% and reduced yield of spring barley and wheat by 24 and 13%,respectively, but had no effect on the yield of spring oats. Based on these results, saflufenacil applied pre-emergence at the proposed dose can be safely used in spring planted barley, oats and wheat; however,the post-emergence application of saflufenacil results in unacceptable injury and yield loss. These resultsare consistent with the proposed pre-emergence use pattern for saflufenacil.

� 2008 Elsevier Ltd. All rights reserved.

1. Introduction

Spring cereals such as barley (Hordeum vulgare L.), oats (Avenasativa L.), and wheat (Triticum aestivum L.) are important cerealcrops in southwestern Ontario. Cereal crops have become morepopular among growers in Ontario in recent years as new improvedvarieties and competitive prices have caused a shift away fromother field crops such as maize and soybean. Cereals are an excel-lent crop to include in a rotation for the control of annual, biennial,and perennial weeds as cereal crops are planted in narrower rowsallowing them to better compete with weeds. The relative earlyharvest of spring cereals provides an excellent opportunity forpost-harvest control of perennial weeds. The fibrous roots systemof cereal crops can also improve soil structure (Tottman, 1980).

Registered herbicide choices for weed control in cereals havenot changed much over the past 10–15 years in Canada.Depending on the weed species present, products such as 2,4-D,MCPA, dichlorprop, dicamba, bromoxynil, thifensulfuron-methyland tribenuron-methyl are still being used, either alone or incombination (Ivany et al., 1990; OMAFRA, 2006; Vencill, 2002).Although these herbicides provide effective control of specific

þ1 519 674 1600.(N. Soltani).

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broadleaved weeds depending on herbicide choice, there may beinjury to sensitive cereal varieties (Sikkema et al., 2007). There arecurrently no soil applied residual herbicides available for broad-leaved weed control in spring cereals. To remain competitiveOntario cereal growers need new weed management options thatprovide selective and consistent control of annual broadleavedweeds in barley, oats, and wheat. More research is needed todetermine tolerance of cereal crops to newly developedherbicides with a novel mode of action.

Saflufenacil (provisionally approved by ISO) is a new herbicidebeing developed globally by BASF for residual pre-emergencebroadleaved weed control in maize and other crops. The proposedsaflufenacil use dose for spring cereals in Ontario is 50 g ai ha�1.Saflufenacil can also be used for pre-plant foliar burndown ofbroadleaved weeds including herbicide resistant biotypes (Anon-ymous, 2008). Saflufenacil is a pyrimidinedione that inhibitsprotoporphyrinogen-IX-oxidase (PPO). Saflufenacil is absorbed byboth roots and foliage in plants. It is mainly translocated in thexylem and has limited mobility in the phloem (Liebl et al., 2008).Susceptible weeds show injury symptoms within a few hours anddie in 1–3 days. Saflufenacil is applied at relatively low doses andhas low environmental, toxicological and eco-toxicological impact(Anonymous, 2008). There is minimal residual carryover withsaflufenacil as the herbicide does not persist in the soil (Anony-mous, 2008).

Table 1Significance of main effects and interactions for percent visible injury, height andyield of spring cerealsa

Main effectsb Spring cereal injury (%) Height(cm)

Yield(t ha�1)

3 DAT 7 DAT 14 DAT 28 DAT

Application timing ** ** ** ** * **Untreated 0 0a 0 0 81a 3.5Pre-emergence 0 1a 0 1 83a 3.6Post-emergence 71 60b 51 33 68b 3.0SE 1 1 2 1 1 0.2

Type of spring cereal NS NS NS NS NS *Barley 31 27 24 17 75 3.5Oats 27 22 17 8 80 4.3Wheat 28 23 21 16 75 2.3SE 5 4 3 3 1 0.1

Saflufenacil dosec

(g ai ha�1)* NS * NS NS NS

0 0 0 0 0 81 3.550 34 28 24 15 76 3.4100 38 33 27 19 75 3.2SE 4 4 3 2 1 0.1

InteractionsT� C NS NS NS NS NS **T�D * NS * * NS NSC�D NS NS NS NS NS NST�D� C NS NS NS NS NS NS

a Means followed by the same letter within a column are not significantly differentaccording to Fisher’s Protected LSD at P< 0.05. Means for a main effect were sepa-rated only if there were no significant interactions involving that main effect.Abbreviations: DAT, days after treatment; T, application timing; C, type of springcereal; D, saflufenacil dose; NS, not significant at P¼ 0.05 level.

b Significance at P< 0.05 and P< 0.01 levels denoted by * and **, respectively.c Post-emergence treatments included Merge (surfactant/solvent) at 1% v/v.

P.H. Sikkema et al. / Crop Protection 27 (2008) 1495–14971496

Pre-emergence and post-emergence applications of saflufenacilcan control troublesome weeds such as Abutilon theophrasti (vel-vetleaf), Ambrosia artemisiifolia (common ragweed), Ambrosiatrifida (giant ragweed), Xanthium strumarium (common cocklebur),Polygonum persicaria (ladysthumb), Amaranthus retroflexus (redrootpigweed), Amaranthus tuberculatus var. rudis (common waterhemp)and Chenopodium album (common lambsquarters) (Anonymous,2008; Liebl et al., 2008). Tolerance of spring barley, oats, and wheatto saflufenacil is not known. If tolerance is adequate, saflufenacilwould provide growers with an additional herbicide mode of actionoption to effectively manage troublesome broadleaved weeds inspring cereals.

The objective of this research was to evaluate tolerance of springcereals (barley, oats, and wheat) to pre-emergence and post-emergence applications of saflufenacil at 50 and 100 g ai ha�1,representing the proposed use dose and twice the proposed usedose in spring cereals, respectively.

2. Materials and methods

Three field studies were conducted at the Huron ResearchStation, Exeter, Ontario over a 2-year period (2006 and 2007). Thesoils for study sites were a Brookston clay loam with 44% sand, 33%silt, 23% clay, 4.1% OM, and pH of 7.9 in 2006; 34% sand, 36% silt, 30%clay, 3.6% OM, and pH of 8.0 at site 1 in 2007; and 31% sand, 38% silt,31% clay, 4.4% OM, and pH of 7.9 at site 2 in 2007. Seedbed prepa-ration consisted of moldboard plowing in the autumn followed bytwo passes with a cultivator with a rolling basket harrows in thespring.

The experimental design was a split–split plot established asa randomized complete block with four replications. Main plotswere application timing (pre-emergence and post-emergence),subplots were type of spring cereal (barley, oat, and wheat), andsub-subplots were dose of saflufenacil (0, 50, and 100 g ai ha�1).Saflufenacil post-emergence treatments included Merge� [surfac-tant blendþ solvent (petroleum hydrocarbons); 1% v/v]. Plots were2 m wide by 10 m long. Spring barley ‘Sunderland’, oat ‘Goslin’, andwheat ‘Winfield’ were seeded with a double disc drill at130 kg ha�1 in rows 17.5 cm apart at a depth of 4 cm on April 19,2006 and April 21, 2007 (both sites).

Pre-emergence herbicides were applied 3 days after planting(DAP) and post-emergence herbicides were applied at Zadoks stage18–22 with a CO2 pressurized backpack sprayer calibrated todeliver 200 L ha�1 at 241 kPa. The boom was 1.5 m long with fourTeejet 8002 flat-fan nozzles tips (Spraying Systems Co., Wheaton,IL, USA) spaced 50 cm apart. All plots including the non-treatedcontrol were kept weed-free by hand weeding.

Visible crop injury was rated on a scale of 0–100% (0¼ no visibleinjury, and 100¼ plant death) at 3, 7, 14, and 28 days after treat-ment (DAT). Ten plants were randomly selected per plot and theheight from the soil surface to the highest growing point of eachplant was measured at 35 DAT. All cereals were harvested on July24, 2006, July 23, 2007, and July 23, 2007 using a plot combine andyields were adjusted to 14.5% moisture.

All data were subjected to analysis of variance. Tests werecombined over locations and years and analyzed using the MIXEDprocedure of SAS (1999). Variances were partitioned into therandom effects of locations, years, locations by years, blocks withinyears by locations, and the interactions with fixed effects (herbicidedose, application timing, and cereal type). Significance of randomeffects was tested using a Z-test of the variance estimate and fixedeffects were tested using F-tests. Error assumptions of the varianceanalyses (random, homogeneous, and normal distribution of error)were confirmed using residual plots and the Shapiro–Wilknormality test. To meet assumptions of the variance analysis,percent injury was arcsine square-root transformed (Bartlett, 1947).

Means were converted back to the original scale for presentation ofresults. Means were separated using Fisher’s protected LSD atP< 0.05.

3. Results and discussion

There was no significant location by year or location by appli-cation timing by cereal type by dose interaction for any variableanalyzed, therefore all experiments were combined and analyzedtogether. Application timing was significant for all variables eval-uated. The application timing by dose interaction was significantfor visible injury at 3, 14 and 28 DAT. Yields were separated basedon a significant cereal type by application timing interaction.

3.1. Visible injury

Visible injury symptoms included whitening followed by chlo-rosis of the leaf tissue and plant height reduction. Saflufenacilapplied pre-emergence caused minimal visible injury (1% or less) at3, 7,14 and 28 days after emergence (DAT) and had no adverse effecton plant height or yield of barley, oats and wheat (Tables 1 and 2).The minimal injury observed with the pre-emergence application ofsaflufenacil in this study is similar to those found with currentlyused post-emergence herbicides in Ontario such as 2,4-D, bro-moxynil plus MCPA, and dichlorprop plus 2,4-D (OMAFRA, 2006;Sikkema et al., 2007; Soltani et al., 2006).

Saflufenacil plus Merge (1% v/v) applied post-emergence causedas much as 76, 60, 52 and 35% visible injury in spring cereals at 3, 7,14 and 28 DAT, respectively (Table 2). Injury with saflufenacil plusMerge applied post-emergence decreased over time and wasgenerally greater as dose increased (Table 2). In other studies, overa 3-year period post-emergence applied herbicides such asdicamba plus MCPA plus mecoprop consistently resulted in cropinjury in winter wheat (Sikkema et al., 2007). Tottman (1977)

Table 3Yield for three types of spring cereals (barley, oats, and wheat) as a function ofsaflufenacil timinga

Type of spring cereal Yield at different application timing (t ha�1) SE (�)

Untreated Pre-emergence Post-emergence

Barley 3.8Z 3.9Z 2.9Y 0.1Oats 4.4Z 4.4Z 4.1Z 0.1Wheat 2.3Z 2.5Z 2.0Y 0.1

a Means followed by the same letter within a row (Y–Z) are not significantlydifferent according to Fisher’s Protected LSD at P< 0.05. Yield of cereals for eachtime of application is means for two saflufenacil doses.

Table 2Percent visible injury of spring cereals at two application timings as a function ofsaflufenacil dosea

Saflufenacil doseb (g ai ha�1)by variable

Injury at different applicationtiming (%)

SE (�)

Pre-emergence Post-emergence

Injury 3 DAT50 0aZ 67aY 4100 0aZ 76bY 5SE (�) 0 1

Injury 14 DAT50 0aZ 45aY 3100 0aZ 52bY 4SE (�) 0 2

Injury 28 DAT50 1aZ 27aY 2100 1aZ 35bY 3SE (�) 0 2

a Means followed by the same letter within a column (a–b) or row (Y–Z) for eachsection are not significantly different according to Fisher’s Protected LSD at P< 0.05.Abbreviations: DAT, days after treatment.

b Post-emergence treatments included Merge (surfactant/solvent) at 1% v/v.

P.H. Sikkema et al. / Crop Protection 27 (2008) 1495–1497 1497

indicated similar results in which underdeveloped seeds wereobserved with post-emergence application of dicamba plus MCPAplus mecoprop. Schroeder and Banks (1989) also found that earlypost-emergence applications of dicamba or dicamba plus 2,4-Dresulted in wheat injury.

3.2. Height

Saflufenacil applied pre-emergence caused no adverse effect onplant height of barley, oats and wheat (Table 1). These results aresimilar to those found with currently used post-emergence herbi-cides in Ontario such as 2,4-D amine, bromoxynil plus MCPA, anddichlorprop plus 2,4-D (OMAFRA, 2006; Sikkema et al., 2007).

Saflufenacil plus Merge applied post-emergence reduced plantheight by as much as 16% (Table 1). There was no differencebetween saflufenacil doses in their effect on plant height (Table 1).Other studies have shown plant height reduction of up to 11% insome cereals with post-emergence herbicides such as dicamba(Quimby and Nalewaja, 1966), dicamba plus MCPA plus mecoprop(Sikkema et al., 2007), dicamba plus 2,4-D amine (Martin et al.,1989), and dicamba plus MCPA (Martin et al., 1989).

3.3. Yield

Saflufenacil applied pre-emergence had no adverse effect onyield of barley, oats and wheat compared to the untreated check(Table 3). This is similar to the yield response of other cereals withcurrently used post-emergence herbicides in Ontario such as 2,4-Damine, bromoxynil plus MCPA, and dichlorprop plus 2,4-D (OMA-FRA, 2006; Sikkema et al., 2007).

Saflufenacil plus Merge (1% v/v) applied post-emergencereduced yield of spring barley and wheat by 24 and 13%, respec-tively, but had no effect on the yield of spring oats (Table 3). Therewas no difference between saflufenacil doses in respect to theireffect on yield of barley, oats and wheat (Table 1). Martin et al.(1989) found that other post-emergence herbicides such asdicamba alone, or in combination with a phenoxy herbicide,reduced yields of some cereals 12–39%. Tottman (1978) also foundthat tankmixes containing dicamba, 2,3,6-TBA, MCPA or mecopropapplied post-emergence to winter wheat can reduce grain yield.The results of this study are consistent with those found by Ivany

et al. (1990), Rinella et al. (2001), and Tottman (1982) who alsonoted cereal yield losses from use of post-emergence herbicidessuch as dicamba.

4. Conclusions

Based on this study, saflufenacil applied pre-emergence at theproposed dose of 50 g ai ha�1 can be safely used in spring plantedbarley, oats, and wheat. However, saflufenacil applied post-emergence results in unacceptable injury in spring planted barley,oats, and wheat. These results are consistent with the proposedpre-emergence 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 Ontario Wheat Producers and BASF.

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