Control of Glyphosate-Resistant Palmer amaranth in DHT Cotton

Control of Glyphosate-Resistant Palmer amaranth in DHT Cotton.

Culpepper and Chaffin; University of Georgia

Braxton and Richburg; Dow AgroSciences

Georgia counties confirmed to be infested with glyphosate-resistant Palmer amaranth.

2004 – 1 county

2005 – 2 counties

2006 – 7 counties

2007 – 10 counties

2008 – 18 counties

Hand weeding cotton during 2009

52 counties surveyed Acres in survey: 799,000 Acres hand weeded: 437,660 54% cotton hand weeded

$3 to $100/A Average $26 $11.4 million

Grower Costs

Acres Hand Weeded

Some of the hand weeding expense was from the removal of plants from the field.

GR Palmer amaranth control in dryland conservation tillage systems

Prowl + Reflex PRE

Roundup + Dual POST

Diuron + MSMA PD

Prowl + Reflex PRE

Ignite + Dual POST

Diuron + MSMA PD

Palmer Amaranth regrowth after being treated with Ignite.

2,4-D- Resistant Cotton Being Developed

2,4-D resistant cotton

2,4-D sensitive cotton

Objective

• Begin to determine the most effective 2,4-D weed management systems for glyphosate-resistant Palmer amaranth.

Experiments

1. Single application study (non-crop)

2. 2,4-D weed management systems (DHT cotton)

Experiment 1: Single Application

Macon County(2 locations)

Tift County(1 location)

Factorial Treatment Arrangement(Experiment 1: Single Application)

2,4-D (Weedar) Option: 0, 1.0, 1.5, or 2.0 pt/A

Ignite Option: 0 or 29 oz/A

Palmer was 8 inch at time of application (15 GPA)

Percent GR Palmer amaranth control at 20 d. Average 3 loc., GA, 2009.

0

20

40

60

80

100

0.5 lb 0.75 lb 1.0 lb1.0 lb 0.25 lb 0.5 lb

2,4-D 2,4-D

69 cd

77 bc

73 bcd

79 b

91 a

92 a

96 a

Ignite

(29 oz)+

Ignite

Non-treated Ignite

12 DAT

Non-treated

12 DAT

1.5 pt 2,4-D

1.5 pt of 2,4-D

12 DAT 24 DAT

Non-treated Ignite + 2,4-D

12 DAT

Experiment 2: Systems

PRE

Prowl

Prowl

Prowl

Prowl

POST (4-6” Palmer)

Weedar

Ignite + Weedar

Ignite

None

Residual programs

Direx + MSMA directed to all systems. Prowl 2.1 pt/A; Reflex 1 pt/A; Ignite 23 oz/A; Weedar 1.5 pt/A; Direx 2 pt/A; MSMA 2 lb ai/A.

TRT

1

2

3

4

Prowl + Reflex

Prowl + Reflex

Prowl + Reflex

Prowl + Reflex

Weedar

Ignite + Weedar

Ignite

None

5

6

7

8

Experiment 2: Systems

POST 1 (4-6“ Palmer)

Weedar

Weedar + Ignite

Ignite

None

POST 2 (3-6” Palmer)

Weedar

Weedar + Ignite

Ignite

None

Total POST programs

Direx + MSMA directed to all systems. Weedar 1.5 pt/A; Ignite 23 oz/A; Direx 2 pt/A; MSMA 2 lb ai/A.

TRT

1

2

3

4

One inch of rainfall occurred within 5 days of planting and PRE treatments. Rainfall continued throughout the season.

Percent GR Palmer amaranth control 28 d after layby. Macon Co. GA, 2009.

0

20

40

60

80

100

86 bc

82 c

20 d

93 ab

99 a

99 a

99 a

2,4-D Ignite + 2,4-D

None

Prowl

Ignite

+ ReflexProwl ProwlProwl

+ Reflex

+ Reflex

+ Reflex

POST 2,4-D Ignite + 2,4-D

None Ignite

82 c

Direx + MSMA directed to all systems.

Percent GR Palmer amaranth control at harvest. Macon Co. GA, 2009.

0

20

40

60

80

100

48 c

50 c

81 b

90 a

90 a

93 a

2,4-D Ignite + 2,4-D

None

Prowl

Ignite

+ ReflexProwl ProwlProwl

+ Reflex

+ Reflex

+ Reflex

POST 2,4-D Ignite + 2,4-D

None Ignite

43 c

Direx + MSMA directed to all systems.

Seed Cotton Yield (lb/A). Macon Co. GA, 2009.

0

300

600

900

1200

490 c

530 c

955 a

1120 a

1080 a

1100 a

2,4-D Ignite + 2,4-D

None

Prowl

Ignite

+ ReflexProwl ProwlProwl

+ Reflex

+ Reflex

+ Reflex

POST 2,4-D Ignite + 2,4-D

None Ignite

140 d

Direx + MSMA directed to all systems.

Percent GR Palmer amaranth control comparing POST and residual programs 28 d after layby .

Macon Co. GA, 2009.

0

20

40

60

80

10099 a

81 c

93

ab

94 a

Ignite + 2,4-D

Prowl+

Reflex

POST Ignite

Ignite

Ignite + 2,4-D 2,4-D

2,4-D

Ignite + 2,4-D

Ignite + 2,4-D

88 b

Direx + MSMA directed to all systems.

POST 2

Non-treated Control (July 5)

Ignite + 2,4-D

Ignite + 2,4-D

2,4-D

2,4-D

Glyphosate-resistant Palmer amaranth response to sequential POST applications. Macon Co., 2009.

0

20

40

60

80

100

93 a

50 c

81 b

85 b

Ignite + 2,4-D

Prowl+

Reflex

POST Ignite

Ignite

Ignite + 2,4-D 2,4-D

2,4-D

Ignite + 2,4-D

Ignite + 2,4-D

50 c

Direx + MSMA directed to all systems.

POST 2

Percent GR Palmer amaranth control with POST programs at harvest . Macon Co. GA, 2009.

0

300

600

900

1200

1100 a

440 b

955 a

1026 a

Ignite + 2,4-D

Prowl+

Reflex

POST Ignite

Ignite

Ignite + 2,4-D 2,4-D

2,4-D

Ignite + 2,4-D

Ignite + 2,4-D

550 b

Direx + MSMA directed to all systems.

POST 2

Seed cotton yields (lb/A) with total POST programs. Macon Co. GA, 2009.

Summary

(Experiment 1, Single Application)

• Ignite (29 oz) controlled GR Palmer amaranth 73%

• 2,4-D (1 to 2 pt) controlled GR Palmer amaranth 69-79%

• Ignite + 2,4-D controlled GR Palmer amaranth 91-96%

Summary

(Experiment 2, Systems)

• Prowl fb 2,4-D or Ignite fb Direx + MSMA controlled Palmer 50%. Mixing Ignite with 2,4-D improved control at least 31%.

• Prowl plus Reflex fb Ignite, 2,4-D, or Ignite + 2,4-D controlled Palmer 90 to 93%.

• Total POST programs with sequential Ignite or 2,4-D applications provided only 50% control. Mixtures of Ignite plus 2,4-D improved control 35%.

At harvest

Summary

(Experiment 2, Systems)

Prowl fb Ignite + 2,4-D fb Direx + MSMA

Prowl + Reflex fb Ignite, 2,4-D or Ignite + 2,4-D fb Direx + MSMA

Sequential Ignite + 2,4-D applications fb Direx + MSMA

Highest seed cotton yields

Conclusions

The addition of 2,4-D in a systems approach offers growers a significant advantage of managing emerged glyphosate-resistant Palmer amaranth

Physical movement of 2,4-D is of great concern; however, research to address this is in progress