EVALUATION OF HERBICIDES FOR BROAD SPECTRUM WEED CONTROL IN IRRIGATED CORN

Joel Felix and Joey Ishida

Oregon State University

Malheur Experiment Station

Ontario, OR, 2009

Introduction

A large proportion of the corn acreage in the United States is planted to Roundup Ready^® hybrids and Roundup^® is the herbicide most often used for weed management on these corn acres. Corn acreage in Malheur County in 2007 was 24,900 acres, which was approximately 42 percent of the total corn acreage in the state of Oregon (USDA NASS 2007). Tembotrione (Laudis^®) is a new herbicide marketed by Bayer CropScience for annual broadleaf and grass weed control in corn. Tembotrione is registered for use on field, silage, and seed corn as well as sweet corn and popcorn. The introduction of Laudis provides growers with a tool to control weeds with resistance to other herbicides and weeds that are difficult to control in glyphosate-based weed management programs. Similarly, a new herbicide from BASF, saflufenacil (Integrity™), was evaluated for possible stand-alone applications when applied pre-plant or tank-mixed with glyphosate for improved and more complete burndown of broadleaf weeds, including those resistant to glyphosate and ALS herbicides. Other herbicide treatments in this study included a premix of glyphosate + s-metolachlor (Sequence^®) and glyphosate + s-metolachlor + mesotrione (Halex^® GT) from Syngenta. The objective of this study was to evaluate newly registered herbicides for corn safety and weed control efficacy under local conditions.

Materials and Methods

A field study was established in 2009 at the Malheur Experiment Station near Ontario, Oregon in a well-drained, furrow-irrigated field previously planted to wheat. The predominant soil at the site was an Owyhee silt loam with 1.74 percent organic matter, a pH of 7.3, and a cation exchange capacity of 13 meq/g of soil. The study area was moldboard plowed and disked on May 1 and beds spaced 30 inches apart were formed on May 8, 2009. Roundup Ready corn ('DK C52-59-RR' [VT3]) was planted with a John Deere model 71 flexi planter on May 11 at 7 ⅞-inch spacing within the row. The study followed a randomized complete block design with four replications. Individual plots were 10 ft wide (4 rows) by 25 ft long. The field was furrow irrigated for 24 hours on May 29, 2009. The corn was fertilized on June 12 to provide 180, 50, and 50 lb/acre nitrogen (N), phosphorus (P), and sulfur (S), respectively. The study was furrow irrigated on a calendar schedule (8 times during the growing season) to maintain moisture in the top 12 inches of the soil profile starting May 29. Early post-emergence (EPOST) herbicide treatments were applied on June 3 and post-emergence (POST) on June 12, 2009. All herbicide treatments were applied using a CO₂-pressurized backpack sprayer with a boom fitted with six 8002EVS Teejet nozzles calibrated to deliver 20 gal/acre at 35 psi and 3 mph. The predominant weeds in the study area were common lambsquarters, pigweed species, and barnyardgrass. Plots were visually evaluated for crop injury and weed control using a 0-100 percent scale (where 0 = no crop injury or no weed control and 100 = complete crop kill or complete weed control) at 5, 17, 34, and 88 days after treatment (DAT). Corn ears were hand harvested from two (15 ft long) center rows on October 26, 2009. The data were subjected to analysis of variance and means separated using the least significant difference (LSD) at P = 0.05. Treatment performance and yield data for Laudis are presented in Tables 1-4, while those for Prowl H₂O, Integrity, Status, Sequence, Halex, and Roundup are presented in Tables 5 and 6.

Results and Discussion

Corn plants were not injured by any of the herbicides tested in this study. Visual evaluation on July 17 indicated control for common lambsquarters and pigweed with Laudis ranged from 99 to 100 percent while control of barnyardgrass was 90 to 95 percent (Table 1). Evaluations on June 29 indicated 100 percent control of common lambsquarters and pigweed species (Table 2). Control for barnyardgrass was 93 to 100 percent and best when Laudis was mixed with atrazine (AAtrex^®). The level of weed control on July 16 was still 100 percent for common lambsquarters and pigweed species (Table 3). Barnyardgrass control was 95 to 100 percent and again best when Laudis was mixed with Aatrex. A late season weed control evaluation was conducted on September 8 (Table 4). Tembotrione provided season-long control for common lambsquarters and pigweed species. Late season control for barnyardgrass was 94 to 99 percent. Corn yield for different herbicide treatments ranged from 245 to 261 bu/acre compared to 233 bu/acre without herbicides.

Control of common lambsquarters and pigweed species with Integrity herbicide on June 17 ranged from 90 to 94 percent (Table 5). Sequence and Halex GT provided 100 percent control for common lambsquarters and pigweed species. Barnyardgrass control with Integrity ranged from 69 to 83 percent while control with Sequence and Halex GT was about 96 percent. All herbicides provided 100 percent control for kochia. Late season control for common lambsquarters, pigweed species, and kochia with Integrity herbicide on September 8 was 100 percent (Table 6). Corn yield with Integrity herbicide ranged from 247 to 256 while that for Sequence and Halex GT was 274 and 265 bu/acre, respectively.

Weed control in furrow-irrigated corn with Laudis and Integrity herbicides was as good as that provided by other registered herbicides. Tank mixing Laudis with Aatrex provided superior weed control. Even though tank mixture did not control weeds better than glyphosate alone, this management strategy can be useful to delay the evolution of glyphosate resistant weeds.

Reference

USDA National Agricultural Statistics Services. 2007. http://www.nass.usda.gov/Data_and_Statistics/County_Data_Files/Release_Schedule/index.asp Accessed December 8, 2009.

Table 5. Corn response and weed control on June 17 with Prowl H₂O, Integrity, Status, Sequence, Halex, and Roundup in Roundup Ready irrigated field corn at the Malheur Experiment Station, Oregon State University, Ontario, OR, 2009.

Weed controlb

Treatment

Rate

Timinga

Corn injury

Common lambsquarters

Pigweed spp

Barnyardgrass

Kochia

----------------------------------- % -----------------------------------

Untreated

0

a

0

f

0

c

0

d

0

b

Integrity (Saflufenacil)

20

fl oz/a

PRE

0

a

91

cd

91

b

79

c

100

a

Pendimethrin (Prowl H2O)

1.8

pt/a

PRE

0

a

94

b

91

b

80

bc

100

a

Dimethenamid-p (Outlook)

16

fl oz/a

PRE

Pendimethrin (Prowl H2O)

1.8

pt/a

PRE

0

a

90

de

93

b

83

abc

100

a

Integrity (Saflufenacil)

20

fl oz/a

PRE

Integrity (Saflufenacil)

13

fl oz/a

PRE

0

a

93

bc

93

b

80

bc

100

a

Glyphosate

22

fl oz/a

POST

NISc

0.4

pt/a

POST

AMS

5

% V/V

POST

Integrity (Saflufenacil)

13

fl oz/a

PRE

0

a

94

b

93

b

69

c

100

a

Glyphosate

22

fl oz/a

POST

Status (diflufenzopyr + dicamba)

2.5

oz/a

POST

NIS

0.4

pt/a

POST

AMS

5

% V/V

POST

s-metolachlor (Dual II Magnum)

2.25

pt/a

PRE

0

a

89

e

91

b

80

bc

100

a

Glyphosate

22

fl oz/a

POST

NIS

0.4

pt/a

POST

AMS

5

% V/V

POST

Sequence (Glyphosate + s-metolachlor)

2.5

pt/a

EPOST

0

a

100

a

100

a

95

ab

100

a

AMS

2.5

% V/V

Halex GT

3.6

pt/a

EPOST

0

a

100

a

100

a

96

a

100

a

NIS

0.8

pt/a

AMS

2.5

% V/V

Glyphosate

22

fl oz/a

POST

0

a

100

a

100

a

98

a

100

a

AMS

2.5

% V/V

Glyphosate

22

fl oz/a

POST

AMS

2.5

% V/V

^aPRE = Pre-emergence; EPOST = Early post-emergence; POST = Post-emergence.

^bMeans within a column followed by the same letter are not significantly different (LSD, P = 0.05).

^cNIS = non-ionic surfactant; AMS = ammonium sulfate.

Table 6. Late season weed control on September 8 and corn yield with Prowl H₂O, Sharpen, Status, Sequence, Halex, and Roundup in Roundup Ready irrigated field corn at the Malheur Experiment Station, Oregon State University, Ontario, OR, 2009.

Weed controlb

Treatment

Rate

Timinga

Common lambsquarters

Pigweed species

Barnyard-grass

Kochia

Corn yield

------------------------------- % --------------------------

bu/acre

Untreated

0

c

0

d

0

e

0

c

239

d

Integrity (Saflufenacil)

20

fl oz/a

PRE

90

a

91

ab

43

d

100

a

255

a-d

Pendimethrin (Prowl H2O)

1.8

pt/a

PRE

94

a

94

ab

70

b

100

a

249

bcd

Dimethenamid-p (Outlook)

16

fl oz/a

PRE

Pendimethrin (Prowl H2O)

1.8

pt/a

PRE

89

a

88

b

69

b

100

a

247

bcd

Integrity (Saflufenacil)

20

fl oz/a

PRE

Integrity (Saflufenacil)

13

fl oz/a

PRE

100

a

100

a

91

a

100

a

251

bcd

Glyphosate

22

fl oz/a

POST

NISc

0.4

pt/a

POST

AMS

5

% V/V

POST

Integrity (Saflufenacil)

13

fl oz/a

PRE

100

a

100

a

91

a

100

a

256

a-d

Glyphosate

22

fl oz/a

POST

Status (diflufenzopyr + dicamba)

2.5

oz/a

POST

NIS

0.4

pt/a

POST

AMS

5

% V/V

POST

s-metolachlor (Dual II Magnum)

2.25

pt/a

PRE

99

a

99

ab

98

a

100

a

243

cd

Glyphosate

22

fl oz/a

POST

NIS

0.4

pt/a

POST

AMS

5

% V/V

POST

Sequence (Glyphosate + s-metolachlor)

2.5

pt/a

EPOST

100

a

100

a

95

a

100

a

274

a

AMS

2.5

% V/V

Halex GT

3.6

pt/a

EPOST

100

a

100

a

99

a

100

a

265

abc

NIS

0.8

pt/a

AMS

2.5

% V/V

Glyphosate

22

fl oz/a

POST

100

a

100

a

95

a

100

a

266

ab

AMS

2.5

% V/V

Glyphosate

22

fl oz/a

POST

AMS

2.5

% V/V

^aPRE = Pre-emergence; EPOST = Early post-emergence; POST = Post-emergence.

^bMeans within a column followed by the same letter are not significantly different (LSD, P = 0.05).

^cNIS = non-ionic surfactant; AMS = ammonium sulfate.

Cite as:

 

Felix, J. and Ishida, J.  2010. Evaluation of Herbicides for Broad Spectrum Weed Control in Irrigated Corn. p 18-26. In Shock C.C. (Ed.) Oregon State University Agricultural Experiment Station, Malheur Experiment Station Annual Report 2009, Department of Crop and Soil Science Ext/CrS 131.