Response of winter wheat (<i>Triticum aestivum</i> L.) to autumn applied saflufenacil

doi:10.4236/as.2012.35091

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Vol.3, No.5, 755-758 (2012) Agricultural Sciences

http://dx.doi.org/10.4236/as.2012.35091

Response of winter wheat (Triticum aestivum L.) to

autumn applied saflufenacil

Lynette R. Brown, Nader Soltani*, Christy Shropshire, Peter H. Sikkema

University of Guelph Ridgetown Campus, Ridgetown, Canada; *Corresponding Author: [email protected]

Received 29 May 2012; revised 30 June 2012; accepted 16 July 2012

ABSTRACT

There is limited information on the effect of

saflufenacil application timing when applied in

autumn to winter wheat. Five field experiments

were conducted over a three-year period (2007-

2009) at two locations (Ridgetown and Exeter,

Ontario) to evaluate the tolerance of winter

wheat to autumn applications of saflufenacil

applied pre-plant (PP), pre-emergence (PRE), or

post-emergence (POST) at 25, 50, 100 and 200 g

a.i. ha−1. As the dose of saflufenacil increased,

the amount of injury observed also increased.

By May of the following spring, injury ranged

from 11% to 20% at the 25 to 200 g a.i. ha−1 doses

of saflufenacil. Saflufenacil applied PP and PRE

caused little to no injury in winter wheat. Saf-

lufenacil applied POST and POST + Merge in the

autumn caused up to 41% injury with the POST +

Merge application being the most injurious.

However, this injury was transient with no effect

on winter wheat height or yield the following

summer.

Keywords: Cereals; Injury; Height; Herbicide;

Tolerance; Yield

1. INTRODUCTION

Herbicide application timing is influenced by tillage

system (no-tillage, reduced tillage, conventional tillage),

weed species (annual, biennial or perennial) and type of

crop (wheat, maize or soybean). Spring is a very busy

time of the year for many growers. Consequently, poste-

mergence (POST) herbicide application in winter wheat

may be delayed beyond the optimum application timing

resulting in yield losses due to early weed interference.

Most growers apply herbicides for broadleaf weed con-

trol in winter wheat in the spring, however, by exploring

autumn applied herbicides, growers may be able to 1)

spread out their work load; 2) obtain improved control of

winter annual, biennial and perennial broadleaf weeds;

and 3) increase winter wheat yield due to reduced weed

interference.

Saflufenacil is a herbicide used for broadleaf weed

control that is being investigated in a number of different

crops including maize, soybean, cereal and pulse crops

[1-5]. It has a different mode of action from other com-

monly used herbicides for weed control in winter wheat.

As a result, there have been a number of recent studies

looking at the tolerance of saflufenacil in cereal crops.

However, there is minimal research that has studied the

effect of saflufenacil application timing [pre-plant (PP),

pre-emergence (PRE) and POST] in the autumn.

Research has shown that saflufenacil can be used as an

effective tool to control winter annual weeds such as

Chorispora tenella Pallas (blue mustard), Descurainia

Sophia L. (flixweed), Capsella bursa-pastoris L. (shep-

herd’s purse), Thlaspi arvense L. (field pennycress), La-

mium amplexicaule L. (henbit) and perennials such as

Convolvulus arvensis L. (field bindweed) and Taraxacum

officinale Weber (dandelion) [6-8]. There is potential for

saflufenacil to be used with glyphosate as an enhanced

burndown prior to planting wheat as well as providing

residual control of annual broadleaf weeds the following

spring. Since glyphosate-resistant weeds have been docu-

mented in some areas of Ontario, growers will need her-

bicide options other than glyphosate for burndown in

winter wheat. If there is adequate tolerance in winter

wheat to autumn applications of saflufenacil, it may eli-

minate the need for broadleaf herbicides in the spring.

Therefore, the objective of this study was to determine

the sensitivity of winter wheat to autumn applications

(PP, PRE and POST) of saflufenacil at various doses.

2. MATERIALS AND METHODS

A total of five field trials were established over a

three-year period (2007-2009) at the Huron Research

Station near Exeter, ON and the University of Guelph

Ridgetown Campus, Ridgetown, ON. The soil character-

ristics for each field trial are presented in Table 1.

The experiments were established as a 2-way factorial

and plots were arranged in n RCBD with four replica- a

L. R. Brown et al. / Agricultural Sciences 3 (2012) 755-758

756

Table 1. Soil characteristics at Exeter and Ridgetown, ON in 2007-2009.

Location Year Sand (%) Silt (%) Clay (%) OMa (%) pH CEC

Ridgetown 2007 45 29 26 4.9 7.0 11

Exeter 2008 39 37 24 4.3 7.9 38

Ridgetown 2008 52 28 20 5.9 6.4 21

Exeter 2009 28 38 34 4.1 7.9 36

Ridgetown 2009 41 34 25 6.5 6.7 22

aAbbreviation: OM, Organic matter.

tions. Factor one was saflufenacil dose (25, 50, 100 and

200 g a.i. ha−1) and factor two was application timing [PP,

PRE, POST (without adjuvant) and POST plus adjuvant

(Merge; 1.0% v/v)]. Winter wheat “Pioneer 25R47” was

seeded in the autumn at both locations at a rate of 140 -

170 kg·ha−1 in rows that were 17.5 or 19 cm apart in

plots that were 2 m wide by 8 or 10 m long. Pre-plant

herbicides were applied 1 day before planting, Pre-emer-

gence herbicides were applied 3 days after planting and

post-emergence herbicides were applied at 2 - 3 leaf

stage with a CO2-pressurized backpack sprayer equipped

with 120-02 ultra low drift nozzles (Hypro, New Brigh-

ton, MN) calibrated to deliver 200 L·ha−1 at 207 or 241

kPa. A cover spray of bromoxynil/MCPA (560 g a.i. ha−1)

was applied in the spring to maintain the entire experi-

mental area weed free.

Crop injury was evaluated visually 1 and 2 weeks after

treatment (WAT) in the autumn and at the beginning of

May and July of the following year. Crop injury was

evaluated on a scale of 0 (no injury) to 100% (complete

death). Wheat height was measured before harvest from

10 randomly selected plants per plot. Yield was measured

at crop maturity by harvesting the middle 1.5 m of each

plot with a plot combine. Yields were adjusted to 14.5%

moisture.

All data were subjected to analysis of variance using

the PROC MIXED procedure of SAS (software Ver. 9.1,

SAS Institute, Inc., Cary, NC). The assumptions of the

variance analyses (random, homogeneous, normal dis-

tribution of error) were confirmed using residual plots

and the Shapiro-Wilk normality test. To meet the as-

sumptions of variance analyses, the July injury rating

was log transformed. Data were converted back to origi-

nal scale for presentation of results. Injury 1 and 2 WAT

as well as May injury, height and yield data met the as-

sumptions of normality, therefore no transformations

were necessary. Crop injury was not observed at any of

the Ridgetown sites therefore was excluded from analy-

sis and are not shown. Data were combined and analyzed

over environments when possible (i.e. environment by

timing by dose interactions were not significant).

Means were separated using Fisher’s protected LSD.

Type I error was set at 0.05 for all statistical compari-

sons.

3. RESULTS AND DISCUSSION

There was no effect of saflufenacil dose at the PP and

PRE application timings on winter wheat injury 1 WAT

and in May of the following spring (Table 2 ). These re-

sults are consistent with a recent study conducted by

Knezevic et al. [8] that also showed no injury on winter

wheat when saflufenacil (at doses up to 400 g a.i. ha−1)

was applied PRE. There was however, a dose effect

when saflufenacil was applied POST with and without

the adjuvant Merge. At 1 WAT, the POST application of

saflufenacil applied at 100 and 200 g a.i. ha−1 caused 7%

and 10% injury. This injury was transient with 5% injury

observed at the 200 g a.i. ha−1 in the following May.

There was greater injury when saflufenacil was ap-

plied POST + Merge. At 1 WAT, injury from saflufenacil

(25 to 200 g a.i. ha−1) applied POST with Merge was

12% - 18% higher than the POST application without an

adjuvant (Table 2). Similarly, winter wheat injury the

following May from saflufenacil (25 to 200 g a.i. ha−1)

applied POST with Merge was 2% - 9% higher than the

POST application without an adjuvant. Saflufenacil ap-

plied POST with Merge consistently had the greatest

injury at all the doses evaluated.

Other research has also shown that POST applications

of saflufenacil can cause significant injury in cereals.

Frihauf et al. [2] showed that a POST application of

saflufenacil + non-ionic surfactant at 25 to 50 g a.i. ha−1

caused 27% - 38% injury in winter wheat at 1 WAT. In

another experiment, Frihauf et al. [6] showed that in-

creasing saflufenacil doses caused winter wheat injury to

be as high as 30% at 3 - 6 days after treatment. Similarly,

Sikkema et al. [4] showed injury from a POST applica-

tion of saflufenacil at 50 g a.i. ha−1 on spring cereals to

be as high as 67% at 3 days after treatment.

When data were combined for all application timings

(Table 3), saflufenacil applied at 25 to 200 g a.i. ha−1,

caused 4% to 11% injury in winter wheat 2 WAT with the

POST + Merge application ausing the greatest injury c

L. R. Brown et al. / Agricultural Sciences 3 (2012) 755-758 757

Table 2. Winter wheat injury as a function of saflufenacil application timing and dose. Means followed by the same letter within a

column (a-e) or row (X-Z) for each section are not significantly different according to Fisher’s Protected LSD at P < 0.05a.

Injury at various application timings %

Saflufenacil dose (g a.i. ha−1)

PP PRE POST POST + Merge

1 WAT injuryb

0 0 a Z 0 a Z 0 a Z 0 a Z 0

25 0 a Z 0 a Z 4 a Z 16 b Y 1

50 0 a Z 0 a Z 5 ab Z 19 c Y 2

100 2 a Z 1 a Z 7 bc Z 24 d Y 2

200 1 a Z 2 a Z 10 c Z 28 e Y 2

SE 0 0 1 1

May injuryc

0 0 a Z 0 a Z 0 a Z 0 a Z 0

25 0 a Z 2 a Z 1 a Z 3 b Z 1

50 1 a Z 1 a Z 1 a Z 9 c Y 1

100 0 a Z 1 a Z 2 ab Z 7 c Y 1

200 1 a Z 2 a YZ 5 b Y 14 d X 1

SE 0 1 1 1

aAbbreviations: Merge added at 1% v/v; WAT: Weeks after treatment; PP: Pre-plant; PRE: Pre-emergence; POST: Post-emergence; bData averaged for Exeter in

2008 & 2009; cExeter 2008.

Table 3. Winter wheat injury, height and yield as a function of saflufenacil dose and application timing. Means followed by the same

letter within a column are not significantly different according to Fisher’s Protected LSD at P < 0.05a.

Injury%

2 WATb Mayc Julyb Heightd cm Yieldd MT ha−1

Saflufenacil dose (g a.i. ha−1)

0 0 a 0 a 0 a 79.9 a 6.87 a

25 4 b 11 b 1 a 79.6 a 6.68 a

50 5 b 11 b 1 a 80.0 a 6.73 a

100 8 c 18 c 1 a 79.5 a 6.60 a

200 11 d 20 c 1 a 79.8 a 6.55 a

SE 1 2 0 0.2 0.05

Application timing

Untreated 0 a 0 a 0 a 79.9 a 6.87 a

PP 1 a 1 a 0 a 80.2 a 6.87 a

PRE 1 a 2 a 0 a 80.2 a 6.85 a

POST 6 a 16 b 1 a 79.6 a 6.68 a

POST + Merge 20 b 41 c 1 a 79.1 a 6.35 a

SE 1 2 0 0.2 0.05

aAbbreviations: Merge added at 1% v/v; WAT, week after treatment; PP, pre-plant; PRE, pre-emergence; POST, post-emergence; bData averaged for Exeter in

008 & 2009; cExeter 2009; dData averaged for Exeter and Ridgetown in 2007-2009. 2

L. R. Brown et al. / Agricultural Sciences 3 (2012) 755-758

758

(20%). Saflufenacil caused 11% (25 and 50 g a.i. ha−1),

18% (100 g a.i. ha−1) and 20% (200 g a.i. ha−1) injury in

May of the following spring in winter wheat with the

greatest injury occurring with the POST (16%) and

POST + Merge (41%) applications (Table 3). As the

season progressed into July, there was little to no injury

from saflufenacil application the previous autumn.

There was no effect of saflufenacil on winter wheat

height or yield (Table 3). Even though saflufenacil ap-

plied POST and POST + Merge caused up to 16% and

41% injury respectively, this injury was transient with no

effect on winter wheat height or yield. These results dif-

fer from studies conducted by Knezevic et al. [8] who

reported a significant yield reduction (up to 66%) with

autumn POST applications of saflufenacil and up to 67%

with spring POST applications in winter wheat.

4. CONCLUSION

This study concludes that there is an acceptable mar-

gin of crop safety in winter wheat to PP and PRE appli-

cations of saflufenacil. The POST applications caused

injury that would be unacceptable to growers even

though in this study it did not result in a yield loss. There

was greater injury when saflufenacil was applied POST +

Merge. Injury was the greatest at higher doses. Since this

research has shown that saflufenacil can be applied

safely to winter wheat either PP or PRE future research

should focus on the control of winter annual, biennial

and perennial broadleaf weeds. The autumn application

of saflufenacil may eliminate the need for spring applied

herbicides for broadleaf weed control.

5. ACKNOWLEDGEMENTS

The authors would like to acknowledge Todd Cowan for his exper-

tise and technical assistance in these studies. Funding for this project

was provided in part by the Grain Farmers of Ontario (GFO) and

BASF.

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