Weed Management in Corn Questions from Ontario Farmers · PDF fileWeed Management in Corn Questions from Ontario ... Lady's thumb Lamb's-quarters Flower-of-an-hour ... I have used

Peter H. Sikkema

Eastern Ontario Crop

Conference

Kemptville, ON

February 23, 2012

Weed Management in Corn

Questions from Ontario Farmers

Untreated check

Giant ragweed in corn Volunteer RR corn in corn

High rate Roundup

applied late

Primextra; Roundup

I seeded RR corn after RR

corn and noticed I have

some volunteer RR corn.

a. What can I do to control

it?

b. What is the effect on

corn yield?

Question # 1

Poor control of volunteer RR

corn in RR corn 15

6

16

0

0

0

0

0

0 20 40 60 80 100

Roundup

Liberty

Roundup + Liberty

Elim

Accent

Ultim

Option

Summit

Average of 3 studiesNurse, AAFC

Sikkema, UG

Volunteer RR corn control (%) – 56 DAA

Volunteer RR corn in RR

corn can reduce yield

252 249 245 241 234 232 228

0

50

100

150

200

250

300

Weed Free 3000 6000 12000 18000 24000 30000

Volunteer RR corn density (#/acre)

Average of 3 experiments

Yie

ld (

bu/a

c)

Nurse, AAFC

Sikkema, UG

1. There are no effective postemergence herbicides for the control of volunteer RR corn in RR corn

a. Interrow cultivation (UM)

2. Yield loss is correlated with density and environment

a. Up to 10% yield loss at 30000 plants/acre (UG)

b. Up to 13% yield loss at 16000 plants/acre (SDSU)

c. Up to 19% yield loss at 21000 plants/acre (UM)

Summary

Volunteer RR corn in RR

corn can reduce yield

I sprayed my corn at the 6? leaf stage and I noticed

some weeds that came up after application.

Will they reduce corn yield?

Is it worth it to spray again?

Question # 2

Weed free to 2-leaf Weed free to 10-leaf


Weed free to 6-leaf

Weed free to 8-leaf

Weedy check

Experimental Design

Weed free to 10-leaf

61

82

91 97 99

0

20

40

60

80

100

2 4 6 8 10

Corn leaf stage at last Roundup application

Average of 13 weed species in 11 experiments

Weed C

ontr

ol (%

) – 4

2 D

AA

End of season weed control improves

the longer the corn is kept weed free

Nurse, AAFC

Sikkema, UG

Everman, MSU

Sprague, MSU

Keep corn weed-free until at

least the 6-leaf stage

105

185 198

206 207 206 204

0

50

100

150

200

250

Weedycheck

2 4 6 8 10 Weed freecheck

Corn leaf stage at last Roundup application


Yie

ld (

bu

/ac)

Nurse, AAFC

Sikkema, UG

Everman, MSU

Sprague, MSU


Weed free to 6-leaf

Weed free to 8-leaf

Weedy check

Weed free to 10-leaf



1. To be conservative, and to avoid any yield loss, corn should be kept weed free until the 6-leaf stage

2. In our studies, if corn was kept weed free until the …

a. 2-leaf state - there was no yield loss 45% of the time

b. 4-leaf stage - there was no yield loss 82% of the time

c. 6-leaf stage - there was no yield loss 100% of the time

3. There are other benefits to controlling late emerging weeds

a. Improved harvest efficiency

b. Reduced weed seed return to the soil and therefore reduced weed density the following years

Summary



My weeds are pretty big, should I increase the

rate of Roundup?

Question # 3

0

20

40

60

80

100

Lady's thumb Lamb's-quarters Flower-of-an-hour

Mustard, wild Pigweed

10 cm weeds 20 cm weeds 30 cm weeds

Weed C

on

trol (%

)

Nurse, AAFC

Sikkema, UG

Everman, MSU

Sprague, MSU

Decrease in weed control with

Roundup as the weeds get bigger

0

20

40

60

80

100

Ragweed Smartweed, green Velvetleaf Foxtail, green

10 cm weeds 20 cm weeds 30 cm weeds

Weed C

on

trol (%

)

Nurse, AAFC

Sikkema, UG

Everman, MSU

Sprague, MSU

Decrease in weed control with

Roundup as the weeds get bigger

50

60

70

80

90

100

10 20 30

Weed size (cm)

112.5 225 450 675 900 1350

Weed C

ontr

ol (%

) -

42 D

AA

Sikkema, UG

Increase the rate of Roundup as

weeds get bigger

Ragweed control

203 195

181

159

0

50

100

150

200

250

Weed Free 10 cm 20 cm 30 cm

Weed size at the time of herbicide application


Yie

ld (

bu/a

c)

Nurse, AAFC

Sikkema, UG

Corn yield decreases as weed size at

time application increases

1. Weed control decreases as size at the time of application increases

2. Increasing the rate of glyphosate partially overcomes the problem

3. Corn yield consistently decreases as weed size at the time of application increases

a. 10 com weeds – reduction in corn yield of 8 bu/ac

b. 20 com weeds – reduction in corn yield of 22 bu/ac

c. 30 com weeds – reduction in corn yield of 44 bu/ac

Summary

Weed Size

Peter, I planned to spray much earlier but due to

frequent rain events I could not. My corn is now at

the 10-leaf stage and the weeds are more than 12

inches in height.

How high a rate of Roundup can I use and not hurt

my RR corn?

Question # 4

Untreated check High rate Roundup applied late

High rates and late application of

Roundup can injure RR corn

0 0

2

5

0 0

3

12

0

3

6

9

12

15

0.67 1.33 2.67 5.33

Roundup Weathermax Rate (Litres/acre)

8-leaf stage 10-leaf stage

Cro

p I

nju

ry (

%)

– 1

4 D

AA

Nurse, AAFC

Sikkema, UG

Everman, MSU

Sprague, MSU

1. Leaf tissue deterioration

a. Breakdown of tissue of the leaf that was in the whorl at the time of application

b. Usually only one leaf is affected (sometimes two)

2. Leaf wrapping

a. Looks similar to Banvel injury

3. Stem leans over 900 to 1200 cm above the ground

4. Cob deformity

What does it look like?

Roundup injury symptoms in RR corn

High rates and late

application of Roundup

can injure RR corn

9.9 9.8 9.7 9.2

9.9 9.7

8.7 8.1

0

2

4

6

8

10

0.67 1.33 2.67 5.33



Co

b D

efo

rmity (

1-1

0)


Roundup can cause cob deformity

Nurse, AAFC

Sikkema, UG

Everman, MSU

Sprague, MSU

8-leaf; 5.33 L/ac 8-leaf; 2.67 L/ac

10-leaf; 1.33 L/ac

10-leaf; 2.67 L/ac

8-leaf; 1.33 L/ac

10-leaf; 5.33 L/ac

High rates and late

application of Roundup

can cause cob deformity

220 219 219 219 210

220 213 217

209 197

0

50

100

150

200

250

Weed FreeCheck

0.67 1.33 2.67 5.33



Co

rn Y

ield

(b

u/a

c)


Roundup can reduce RR corn yield

Nurse, AAFC

Sikkema, UG

Everman, MSU

Sprague, MSU

1. No injury and yield loss with labeled rates and application timing

2. At 8-leaf stage there was minimal injury and no yield loss at rates up to 2.67 L/ac

a. 10 bu/ac yield loss at 5.33 L/ac

3. At 10-leaf stage there was minimal injury and no yield loss at rates up to 1.33 L/ac

a. 11 bu/ac yield loss at 2.67 L/ac

b. 23 bu/ac yield loss at 5.33 L/ac

4. To summarize

a. Increased injury with higher rates of Roundup

b. Increased injury as application was delayed

Summary

Injury and yield loss increase as the rate is

increased and application is delayed

Peter, I have no-till RR corn where I planned to put on

my preplant burndown. The corn was seeded and

it has rained ever since. I have huge dandelions

and other perennials, biennials and winter annuals.

The corn has emerged.

How high a rate of Roundup can I use and not injure

the corn?

Question # 5

Very little injury from high rates of

Roundup applied early in RR corn

0 0 0

1

0 0 0

2

0

2

4

6

8

10

0.67 1.33 2.67 5.33


Spike - 1 leaf 1-2 leaf stage

Cro

p I

nju

ry (

%)

– 2

8 D

AA

Sikkema, UG

9.9 9.9 9.7 9.7 9.8 9.9 9.8 9.5

0

2

4

6

8

10

0.67 1.33 2.67 5.33



Co

b D

efo

rmity (

1-1

0)

Sikkema, UG

Very little cob deformity from high rates of


229 226 227 228 225 229 227 223 222 221

0

50

100

150

200

250

Control 0.67 1.33 2.67 5.33



Co

rn Y

ield

(b

u/a

c)

Sikkema, UG

Very little yield loss from high rates of


1. Very little impact of high rates of Roundup applied early in RR corn in respect to …

a. Visible crop injury

b. Cob deformity

c. Cob length

d. Maturity

e. Yield

Summary

Very little Injury and yield loss from high

rates of Roundup applied early in RR corn

I have used Roundup for weed control in corn for the

past few years. I am happy with the weed control

at the end of the season but it works so slow. I am

convinced that I am losing yield because Roundup

is such a slow acting herbicide.

What can I add to Roundup to increase the speed of

control and thereby increase my corn yield?

Question # 6

Speed of Roundup

0 20 40 60 80 100

Roundup alone

Ammonium Sulfate

Atrazine

Distinct

Marksman

Pardner + Atrazine

Callisto + Atrazine

Impact + Atrazine

Primextra

Elim

Weed Control (%) - 3 DAA

Average of 13 weed species in 7 experiments

Roundup Tankmixes

Sikkema, UG

Roundup plus …

Speed of Roundup

0 20 40 60 80 100

Roundup alone

Ammonium Sulfate

Atrazine

Distinct

Marksman

Pardner + Atrazine

Callisto + Atrazine

Impact + Atrazine

Primextra

Elim

Pigweed Control (%) - 3 DAA

Summary of 4 studies

Roundup Tankmixes

Sikkema, UG

Roundup plus …

Speed of Roundup

0 20 40 60 80 100

Roundup alone

Ammonium Sulfate

Atrazine

Distinct

Marksman

Pardner + Atrazine

Callisto + Atrazine

Impact + Atrazine

Primextra

Elim

Polygonum Species Control (%) - 3 DAA

Summary of 6 evaluations

Roundup Tankmixes

Sikkema, UG

Roundup plus …

Speed of Roundup

0 50 100 150 200 250

Weedy check

Roundup alone

Ammonium Sulfate

Atrazine

Distinct

Marksman

Pardner + Atrazine

Callisto + Atrazine

Impact + Atrazine

Primextra

Elim

Weed free check

Corn Yield (bu/ac)

Summary of 6 studies

Roundup Tankmixes

Sikkema, UG

Roundup plus …

1. The benefits of a tankmix partner was species specific

2. Improved control of …

a. Wild buckwheat and green smartweed with atrazine

b. Velvetleaf, ragweed, lamb’s-quarters, wild buckwheat, lady’s thumb, green smartweed and Eastern black nightshade with Distinct

3. Decreased control of …

a. Pigweed and barnyard grass with atrazine

4. The faster control did not translate into a yield increase

Summary

Speed of Roundup

Peter, there are so many formulations of glyphosate

on the market.

Is there any difference in respect to weed control, crop

tolerance and yield?

Question # 7

0

3

0 0

1

5

0

2

4

6

8

10

1X 2X

Glyphosate Rate

Roundup Weathermax Clearout Wise-up + N-Tank

Cro

p I

nju

ry (

%)

– 1

4 D

AA

Sikkema, UG

Small difference in crop injury among

glyphosate formulations

20.1 20.2 19.9 20.1 20.0 19.5

0.0

5.0

10.0

15.0

20.0

25.0

1X 2X

Glyphosate Rate


Cob L

ength

(cm

)

Sikkema, UG

Small difference in cob length

among glyphosate formulations

9.7 9.1

9.7 9.2

9.7

9.0

0.0

2.0

4.0

6.0

8.0

10.0

1X 2X

Glyphosate Rate


Cob D

efo

rmity (

0-1

0)

Sikkema, UG

Very little difference in cob deformity


229 227 233 232 230 216

0

50

100

150

200

250

1X 2X

Glyphosate Rate


Corn

Yie

ld (

bu/a

c)

Sikkema, UG

Small difference in yield among


45

67

88

46

70

87

51

74

87

0

20

40

60

80

100

0.5X 1X 2X

Glyphosate Rate


Weed C

ontr

ol (%

) -

56 D

AA

Sikkema, UG

Small difference in weed control


Mean of 12 weed species in 4 corn experiments

68

86

96

64

80

95

75

91 96

0

20

40

60

80

100

0.5X 1X 2X

Glyphosate Rate


Weed C

ontr

ol (%

) -

56 D

AA

Sikkema, UG

Small difference in weed control


Mean of 8 weed species in 4 soybean experiments

177 186

203

169

197 203

181 194 188

0

50

100

150

200

250

0.5X 1X 2X

Glyphosate Rate


Corn

Yie

ld (

bu/a

c)

Sikkema, UG

Small difference in corn yield among


Mean of 4 RR corn experiments

1. Generally little difference among glyphosate formulations in …

a. Weed control

b. Crop tolerance

2. However, it appears that Wiseup + N-Tank may …

a. Provide slightly better weed control

b. Cause slightly more crop injury and yield loss

3. The above will need to be confirmed in future studies

Summary

Glyphosate Formulations

I heard about glyphosate resistant weeds and

would like to add more diversity to my weed

management program in RR corn.

What is the best setup program in RR corn?

Question # 8

Roundup Ready Soybean

4

12 16 18

28

42

56

64 64 64 65 65 64 66

72

0

20

40

60

80

Year

Stratus

Market Share - Eastern Canada

Mark

et

Share

(%

)

Roundup Ready Corn

4 7

10 12

21

30

40

56

69

80

90

0

20

40

60

80

100

2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Year

Market Share - Eastern Canada

Stratus

Mark

et

Share

(%

)

Giant Ragweed

2008

One Resistant Site

Giant Ragweed

2009

18 Resistant Sites

Essex county and Pelee Island

Giant Ragweed

2010

29 Resistant Sites

Essex, Kent and Lambton counties

Pelee Island

Giant ragweed in corn

Canada fleabane

8 sites

Essex county

Canada fleabane

2011

69 Resistant Sites

Essex, Kent, Lambton and Elgin

counties

Canada fleabane in Essex county

Two-Pass Programs

86

91

95

98

0 20 40 60 80 100

Roundup EP

Roundup LP

Roundup; Roundup

Residual; Roundup

Average of 11 species in 6 experiments

Weed Control

Sikkema, UG

Weed Control (%) – 56 DAC

Two-Pass Programs

98

98

98

97

98

99

99

99

97

97

99

50 60 70 80 90 100

Marksman

Prowl + Atrazine

Prowl + Marksman

Integrity

Converge + Atrazine

Primextra + Broadstrike

Dual + Broadstrike + Lontrel

Battalion

Atrazine

Primextra

Primextra + Callisto

Average control of 11 species in 6 experiments

Weed control

Sikkema, UG

Weed Control (%) – 56 DAC

PRE Herbicide fb

Roundup POST

Two-Pass Programs

99

96

98

98

99

98

99

99

96

96

99

50 60 70 80 90 100

Marksman

Prowl + Atrazine

Prowl + Marksman

Integrity

Converge + Atrazine

Primextra + Broadstrike

Dual + Broadstrike + Lontrel

Battalion

Atrazine

Primextra

Primextra + Callisto


Common ragweed control

Sikkema, UG

Ragweed Control (%) – 56 DAC

PRE Herbicide fb

Roundup POST

Two-Pass Programs

84

180

177

192

192

194

0 40 80 120 160 200

Weedy check

Roundup EP

Roundup LP

Roundup; Roundup

Residual; Roundup

Weed free check


Corn Yield

Sikkema, UG

Corn Yield (bu/ac)

1. Weed control was reduced with one pass Roundup programs

1. 86% control with Roundup EP

2. 91% control with Roundup LP

2. Corn yield was reduced with the one pass Roundup programs

a. 14 bu/ac less with Roundup EP

b. 17 bu/ac less with Roundup LP

Summary

Two-Pass Programs

3. The best weed control was with the two pass programs

a. 95% control with sequential application of Roundup

b. 98% control PRE residual followed by Roundup

4. Corn yield was maximized with two pass programs

a. Within 2 bu/ac of weed free control

Summary

Two-Pass Programs

5. The PRE residual followed by Roundup POST is recommended

a. Protect the full yield potential of the crop

b. Open the window for the POST Roundup

c. Reduce the selection intensity for glyphosate-resistant weeds

6. The ideal PRE residual herbicide is field specific and depends on

a. Weed species composition

b. Soil texture, pH, OM and CEC

c. Future crops in the rotation

Summary

Two-Pass Programs

Weed Management in Corn

Questions from Ontario Farmers

Untreated check

Giant ragweed in corn Volunteer RR corn in corn

High rate Roundup

applied late

Primextra; Roundup

Peter H. Sikkema

Eastern Ontario Crop

Conference

Kemptville, ON

February 23, 2012

Weed Management in Corn Questions from Ontario Farmers · PDF fileWeed Management in Corn Questions from Ontario ... Lady's thumb Lamb's-quarters Flower-of-an-hour ... I have used

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