2012: Changes in Cotton Weed Management
Practices in Georgia Following the
Development of
Glyphosate-Resistant Palmer Amaranth
Lynn M. Sosnoskie1,2 and A. Stanley Culpepper1
University of Georgia - Tifton
2University of California - Davis
1
Distribution of GR Palmer amaranth
Map credit: R. L. Nichols
Cotton producing regions in US
Map credit: http://www.cottonusa.org/
Glyphosate-resistant cotton:
Changes in weed management
• Shaner (2000) Pest Manage. Sci. 56:320-326.
– Glyphosate use increasing in cotton
– Concomitant decrease in:
•
•
•
•
PS II inhibitors – diuron, fluometuron, prometryn
DNAs – pendimethalin, trifluralin
Arsenates – MSMA
Carotenoid biosynthesis inhibitors - clomazone
Glyphosate-resistant cotton:
Changes in weed management
• Young (2006) Weed Technol. 20:301-307.
– Increase in glyphosate applications:
• 1/crop (1996) to 1.8/crop (2001)
– Decreased use of fluometuron and trifluralin:
• Fluometuron - 27-44% (1992-1998) to 20-27% (1999-2001)
• Trifluralin – 52-67% (1992-1999) to 30-39% (2000-2001)
• Glyphosate – 30-36% (1998-1999) to 56-57% (2000-2001)
Objective:
To determine if cotton weed
management practices in Georgia
have changed following the
development of glyphosate-resistant
Palmer amaranth
Survey development and administration
• Two surveys (growers and extension agents)
• Surveys were designed by the authors and reviewed by an
expert committee consisting of: extension agents, University
(UGA and other) research scientists, UGA rural sociologist,
industry personnel
• Surveys were ‘identical’ except for the fact that the growers
were asked (anonymously) about their individual farming
practices and agents provided 3rd party information about
county-wide activities
Survey development and administration
• Final survey was 8 pages long, contained 19
questions, and was administered in person
• Survey sections:
– Commodities/acreage
– Herbicide use
– Additional weed management practices
• Tillage, cultivation, hand-weeding
– Weed problems
• Including the presence and severity of
glyphosate-resistant Palmer amaranth
BEFORE
2000-2005
AFTER
2006-2010
Survey development and administration
• E-mail was sent to all Georgia extension agents with cotton
responsibilities (2010) describing the survey and requesting
that they and 3-5 ‘representative’ growers in their county
participate in the process
• Grower qualifications:
– Cotton production
– Responsible for making (agricultural) decisions on their
property
– Did not work for a chemical manufacturer, distributor, of
retailer, nor a seed company
County Data
2009 Georgia Farm Gate Value Report (AR-10-01)
County *
Cotton acres
Value (Millions)
Cotton rank
Total commodity rank
Berrien
21,804
$14.3
18
41
Candler
9,000
$6.5
35
79
Grady
22,403
$17.0
14
16
Irwin
28,269
$20.5
10
43
Macon
9,781
$6.4
36
11
Miller
28,366
$21.6
8
47
Randolph
7,229
$6.0
40
73
Seminole
24,369
$14.1
20
56
Screven
12,822
$12.1
24
62
Sumter
17,697
$11.5
25
26
Taylor
452
$0.2
77
88
Terrell
15,466
$9.5
16
75
Tift
18,820
$12.2
23
19
Thomas
25,858
$17.3
13
37
Turner
20,879
$15.1
16
54
Worth
49,185
$37.8
4
21
* Extension agent from Colquitt County also returned a survey (54,010 acres, $42.1 Million, Rank = 2).
Total grower (n = 65) acres = 129,615
(12.6% of GA cotton)
Total agent county (n = 10) acres = 246,034
(24% of GA cotton)
Commodities - example
Grower Question 4: How many acres do you farm?____________________
Grower Question 5: What types of agricultural commodity groups do you produce on your farm?
Yes
No
Approximate number of acres
or number of heads, houses or
ponds
Row and forage crops
___
___
_____________________
Poultry and eggs
___
___
_____________________
Livestock and aquaculture
___
___
_____________________
Forestry products
___
___
_____________________
Vegetables
___
___
_____________________
Ornamental horticulture
___
___
_____________________
Other (Please describe)
(Continued on next page)
Commodity composition of growers' farms
120.0
Percent (%) of surveyed growers
100.0
100.0
80.0
60.0
36.9
40.0
35.4
18.5
20.0
3.1
3.1
3.1
Ornamentals
and turf
Other
0.0
Row and forage Poultry and
eggs
Livestock and
aquaculture
Forestry
Vegetables
Herbicides - example
Grower Question 9: What herbicides have you relied on for weed control in cotton before (20002005) and after (2006-2010) the development of glyphosate-resistant Palmer amaranth (pigweed)?
On what percent of you row crop acreage have you used each product?
PREPLANT and PREEMERGENCE (burndown (including early), applications made at or prior to
planting, and applications made prior to cotton emergence):
Before (2000-2005):
Yes No Average % of Acres
After (2006-2010):
Yes No Average % of Acres
Roundup, Glyphomax,
Touchdown, others
___ ___ _________________
___ ___ _________________
2,4-D
___ ___ _________________
___ ___ _________________
Aim
___ ___ _________________
___ ___ _________________
Clarity
___ ___ _________________
___ ___ _________________
Valor SX
___ ___ _________________
___ ___ _________________
Direx, others
___ ___ _________________
___ ___ _________________
Firestorm, Parazone,
Gramoxone Inteon
___ ___ _________________
___ ___ _________________
(Continued on next page)
Herbicides - example
Herbicides are not divided up/grouped by MOA, activity,
selectivity
Grouped by timing of application as expressed in
Georgia Pest Management handbook
(http://www.ent.uga.edu/pmh/).
1. PREPLANT and PREEMERGENCE (burndown (including early),
applications made at or prior to planting, and applications made
prior to cotton emergence):
2. POSTEMERGENCE OVER-THE-TOP (following cotton emergence):
3. POSTEMERGENCE DIRECTED:
Growers: Pre-plant herbicides applied
Percent (%) of acres treated
100
Percent (%) of acres treated
90
86.1
*
80
73.7
70
60
50
40
*
38.6
34.2
*
24.7
29.4
30
14.9
20
10
0.5
0
2006-2010
Paraquat
2000-2005
2006-2010
2,4-D
2000-2005
2006-2010
2000-2005
2006-2010
2000-2005
Glyphosate
Glufosinate
Agents: Pre-plant herbicides applied
Percent (%) of acres treated
100
Percent (%) of acres treated
90
87.5
74.3
80
*
70
58.9
60
*
50
37.5
40
30
23
23.3
*
11.8
20
10
0.3
0
2006-2010
Paraquat
2000-2005
2006-2010
2,4-D
2000-2005
2006-2010
2000-2005
2006-2010
2000-2005
Glyphosate
Glufosinate
Growers: Pre-plant*/PRE herbicides applied
Percent (%) of acres treated
100
*
90
81
Percent (%) of acres treated
80
70
*
60
45.8
50
40
*
37.8
26.9
30
25.1
26.9
24.7
15.1
20
8.1
10
2.8
0
2000-2005 2006-2010 2000-2005 2006-2010 2000-2005 2006-2010 2000-2005 2006-2010 2000-2005 2006-2010
Diuron
Fluometuron
Pyrithiobac
Flumioxazin *
Fomesafen
Agents: Pre-plant*/PRE herbicides applied
Percent (%) of acres treated
100
90
Percent (%) of acres treated
80
*
70
58
60
50
*
40
*
25.5
30
29.1
20
10
6.7
8.1
11.2
11.7
3.4
11.2
2.7
0
2000-2005 2006-2010 2000-2005 2006-2010 2000-2005 2006-2010 2000-2005 2006-2010 2000-2005 2006-2010
Diuron
Fluometuron
Pyrithiobac
Flumioxazin
*
Fomesafen
PPI herbicides applied
Percent (%) of acres treated
Percent (%) of acres treated
100
90
80
70
*
75.9
69.9
68.5
60
50
37
40
29.6
30
25.2
16.9
20
11
10
0
Pendimethalin
Agents
AGENTS
2006-2010
2000-2005
Growers
GROWERS
2006-2010
Trifluralin
2000-2005
2006-2010
2000-2005
2006-2010
2000-2005
Pendimethalin
Trifluralin
Growers: POST herbicides applied
Percent (%) of acres treated
100
Percent (%) of acres treated
90
94.4
*
88.4
80
*
70
54.4
60
45.7
50
*
40
40.8
29.7
30
16.3
20
10
0.6
0
2000-2005 2006-2010 2000-2005 2006-2010 2000-2005 2006-2010 2000-2005 2006-2010
Glyphosate
Glufosinate
Pyrithiobac
S-metolachlor
Agents: POST herbicides applied Percent
(%) of acres treated
100
Percent (%) of acres treated
90
80
95
*
74.7
70
60
50
*
33.5
40
38.3
*42
40.3
30
20
11.9
10
0.5
0
2000-2005 2006-2010 2000-2005 2006-2010 2000-2005 2006-2010 2000-2005 2006-2010
Glyphosate
Glufosinate
Pyrithiobac
S-metolachlor
Growers: PD herbicides applied
Percent (%) of acres treated
100
Percent (%) of acres treated
90
80
70
67.9
61.6
60
50
*
46.3
63.3
60
59.3
40
*
*
30
25.5
23.1
20
9.6
10
0
0
2006-2010
Flumioxazin
2000-2005
2006-2010
Diuron
2000-2005
2006-2010
MSMA
2000-2005
2006-2010
2000-2005
2006-2010
2000-2005
Glyphosate
S-metolachlor
Agents: PD herbicides applied
Percent (%) of acres treated
100
Percent (%) of acres treated
90
70
68.5
60
*
50
40
40
*74
*70
80
41
*
29.5
34
30
*
20
9.2
10
5.4
3.5
0
2006-2010
Flumioxazin
2000-2005
2006-2010
Diuron
2000-2005
2006-2010
MSMA
2000-2005
2006-2010
2000-2005
2006-2010
2000-2005
Glyphosate
S-metolachlor
Growers: Changes in glyphosate and glufosinate
applications from 2000-2005 to 2006-2010
3.0
Number of applications / year
2.3
2.4
2.5
2.0
*1.5
1.5
1.0
0.5
0.0
0.0
2000-2005
2006-2010
Glyphosate applications
2000-2005
2006-2010
Glufosinate applicatons
Agents: Changes in glyphosate and glufosinate
applications from 2000-2005 to 2006-2010
2.5
Number of applications / year
2.2
2.0
*2.0
1.8
1.5
1.0
0.5
0.2
0.0
2000-2005
2006-2010
Glyphosate applications
2000-2005
2006-2010
Glufosinate applicatons
Growers
2000-2005: Herbicide costs = $32.30/A
2006-2010: Herbicide costs = $62.50/A
Agents
2000-2005: Herbicide costs = $27.80/A
2006-2010: Herbicide costs = $68.00/A
Additional practices - example
Grower Question 13: Have you ever hand-weeded cotton due to insufficient chemical
or mechanical weed control before (2000-2005) and after (2006-2010) the development
of glyphosate-resistant Palmer amaranth (pigweed)?
Before (2000-2005):
Yes No Average % of Acres
___ ___ ___________________
After (2006-2010):
Yes No Average % of Acres
___ ___ ___________________
Grower Question 14: Please estimate the cost of hand-weeding in cotton before (20002005) and after (2006-2010) the development of glyphosate-resistant Palmer amaranth
(pigweed).
Before (2000-2005):
After (2006-2010):
____________________________$/Acre
___________________________$/Acre
(Continued on next page)
2000-2005: 17% of growers hand-weeded
5% cotton acres at $2.40/A
2006-2010: 92% of growers hand-weeded
52% cotton acres at $23.70/A
Photo by A.C. York 2010
2000-2005: According to agents, growers
hand-weeded 3% cotton acres at $3.50/A
2006-2010: According to agents, growers
hand-weeded 66% cotton acres at $21.70/A
Photo by A.C. York 2010
Growers: Changes in tillage/planting practices
from 2000-2005 to 2006-2010
50.0
43.0
45.0
Percent (%) of acres
40.0
36.3
35.2
36.1
2006-2010
2000-2005
35.0
28.0
30.0
25.0
21.4
20.0
15.0
10.0
5.0
0.0
2000-2005
2006-2010
Strip into weeds
2000-2005
Strip into cover crops
2006-2010
Conventional
Agents: Changes in tillage/planting practices
from 2000-2005 to 2006-2010
50.0
45.0
40.9
43.2
2000-2005
2006-2010
Percent (%) of acres
40.0
35.0
35.0
27.8
29.0
30.0
24.1
25.0
20.0
15.0
10.0
5.0
0.0
2000-2005
2006-2010
Strip into weeds
2000-2005
2006-2010
Strip into cover crops
Conventional
In-row cultivation
• Growers:
2000-2005: 34.3% of cotton acres cultivated
2006-2010: 43.9% of cotton acres cultivated
• Agents:
2000-2005: 13.1% of cotton acres cultivated
2006-2010: 32.1% of cotton acres cultivated
Growers: Most troublesome weed*
Percent (%) of growers surveyed
120
100
80
60
2000-2005
40
2006-2010
20
0
* Summed averages are greater than 100% because of multiple votes for most troublesome species/grower
Growers: 2nd Most troublesome weed*
100
Percent (%) of growers surveyed
90
80
70
60
50
40
30
2000-2005
2006-2010
20
10
0
* Summed averages are greater than 100% because of multiple votes for most troublesome species/grower
Agents: Most troublesome weed
Percent (%) of agents surveyed
120
100
80
60
2000-2005
40
20
0
2006-2010
Agents: 2nd Most troublesome weed
100
Percent (%) of agents surveyed
90
80
70
60
50
40
30
20
10
0
2000-2005
2006-2010