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
1University of Georgia - Tifton2University of California - Davis
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 Data2009 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 - exampleGrower 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)
100.0
3.1
36.9 35.4
18.5
3.1 3.10.0
20.0
40.0
60.0
80.0
100.0
120.0
Row and forage Poultry andeggs
Livestock andaquaculture
Forestry Vegetables Ornamentalsand turf
Other
Perc
ent (
%) o
f sur
veye
d gr
ower
s
Commodity composition of growers' farms
Herbicides - exampleGrower Question 9: What herbicides have you relied on for weed control in cotton before (2000-2005) 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): After (2006-2010):Yes No Average % of Acres 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 - exampleHerbicides 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 appliedPercent (%) of acres treated86.1
73.7
34.238.6
14.9
29.4
0.5
24.7
0
10
20
30
40
50
60
70
80
90
100
2000-2005
2006-2010
2000-2005
2006-2010
2000-2005
2006-2010
2000-2005
2006-2010
Glyphosate 2,4-D Paraquat Glufosinate
Perc
ent (
%) o
f acr
es tr
eate
d *
* *
Agents: Pre-plant herbicides appliedPercent (%) of acres treated
87.5
74.3
23.3
58.9
23
37.5
0.3
11.8
0
10
20
30
40
50
60
70
80
90
100
2000-2005
2006-2010
2000-2005
2006-2010
2000-2005
2006-2010
2000-2005
2006-2010
Glyphosate 2,4-D Paraquat Glufosinate
Perc
ent (
%) o
f acr
es tr
eate
d
*
*
*
Growers: Pre-plant*/PRE herbicides appliedPercent (%) of acres treated
37.8
45.8
26.9
15.1
25.1 24.7
2.8
26.9
8.1
81
0
10
20
30
40
50
60
70
80
90
100
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
Perc
ent (
%) o
f acr
es tr
eate
d
*
*
*
*
Agents: Pre-plant*/PRE herbicides applied Percent (%) of acres treated
3.4
25.5
6.7 8.1 11.2 11.7
2.7
29.1
11.2
58
0
10
20
30
40
50
60
70
80
90
100
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
Perc
ent (
%) o
f acr
es tr
eate
d
*
*
*
*
PPI herbicides appliedPercent (%) of acres treated
69.9
75.9
29.6 25.237
68.5
1116.9
0
10
20
30
40
50
60
70
80
90
100
2000-2005
2006-2010
2000-2005
2006-2010
2000-2005
2006-2010
2000-2005
2006-2010
Pendimethalin Trifluralin Pendimethalin Trifluralin
Growers Agents
Perc
ent (
%) o
f acr
es tr
eate
d
GROWERS AGENTS
*
Growers: POST herbicides appliedPercent (%) of acres treated
94.488.4
0.6
29.7
40.8
45.7
16.3
54.4
0
10
20
30
40
50
60
70
80
90
100
2000-2005 2006-2010 2000-2005 2006-2010 2000-2005 2006-2010 2000-2005 2006-2010
Glyphosate Glufosinate Pyrithiobac S-metolachlor
Perc
ent (
%) o
f acr
es tr
eate
d
*
*
*
Agents: POST herbicides applied Percent (%) of acres treated
95
74.7
0.5
33.538.3 40.3
11.9
42
0
10
20
30
40
50
60
70
80
90
100
2000-2005 2006-2010 2000-2005 2006-2010 2000-2005 2006-2010 2000-2005 2006-2010
Glyphosate Glufosinate Pyrithiobac S-metolachlor
Perc
ent (
%) o
f acr
es tr
eate
d *
**
Growers: PD herbicides applied Percent (%) of acres treated
61.6
46.3
63.360 59.3
67.9
0
23.1
9.6
25.5
0
10
20
30
40
50
60
70
80
90
100
2000-2005
2006-2010
2000-2005
2006-2010
2000-2005
2006-2010
2000-2005
2006-2010
2000-2005
2006-2010
Glyphosate MSMA Diuron Flumioxazin S-metolachlor
Perc
ent (
%) o
f acr
es tr
eate
d
*
* *
Agents: PD herbicides appliedPercent (%) of acres treated
68.5
40 41
70
34
74
3.5
9.25.4
29.5
0
10
20
30
40
50
60
70
80
90
100
2000-2005
2006-2010
2000-2005
2006-2010
2000-2005
2006-2010
2000-2005
2006-2010
2000-2005
2006-2010
Glyphosate MSMA Diuron Flumioxazin S-metolachlor
Perc
ent (
%) o
f acr
es tr
eate
d
*
* *
**
Growers: Changes in glyphosate and glufosinate applications from 2000-2005 to 2006-2010
2.3 2.4
0.0
1.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
2000-2005 2006-2010 2000-2005 2006-2010
Glyphosate applications Glufosinate applicatons
Num
ber o
f app
licati
ons /
yea
r
*
Agents: Changes in glyphosate and glufosinate applications from 2000-2005 to 2006-2010
2.2
1.8
0.2
2.0
0.0
0.5
1.0
1.5
2.0
2.5
2000-2005 2006-2010 2000-2005 2006-2010
Glyphosate applications Glufosinate applicatons
Num
ber o
f app
licati
ons /
yea
r
*
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 = $68.00/A
Additional practices - exampleGrower Question 13: Have you ever hand-weeded cotton due to insufficient chemical or mechanical weed control before (2000-2005) and after (2006-2010) the development of glyphosate-resistant Palmer amaranth (pigweed)?
Before (2000-2005): After (2006-2010):
Yes No Average % of Acres Yes No Average % of Acres ___ ___ ___________________ ___ ___ ___________________
Grower Question 14: Please estimate the cost of hand-weeding in cotton before (2000-2005) and after (2006-2010) the development of glyphosate-resistant Palmer amaranth (pigweed).
Before (2000-2005): After (2006-2010):
____________________________$/Acre ___________________________$/Acre
(Continued on next page)
Photo by A.C. York 2010
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
Growers: Changes in tillage/planting practices from 2000-2005 to 2006-2010
28.0
21.4
36.3 35.2 36.1
43.0
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
50.0
2000-2005 2006-2010 2000-2005 2006-2010 2000-2005 2006-2010
Strip into weeds Strip into cover crops Conventional
Perc
ent (
%) o
f acr
es
Agents: Changes in tillage/planting practices from 2000-2005 to 2006-2010
35.0
29.0
24.1
27.8
40.9 43.2
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
50.0
2000-2005 2006-2010 2000-2005 2006-2010 2000-2005 2006-2010
Strip into weeds Strip into cover crops Conventional
Perc
ent (
%) o
f acr
es
In-row cultivation
• Growers:2000-2005: 34.3% of cotton acres cultivated2006-2010: 43.9% of cotton acres cultivated
• Agents:2000-2005: 13.1% of cotton acres cultivated2006-2010: 32.1% of cotton acres cultivated
Growers: Most troublesome weed*
0
20
40
60
80
100
120
Perc
ent (
%) o
f gro
wer
s sur
veye
d
2000-2005
2006-2010
* Summed averages are greater than 100% because of multiple votes for most troublesome species/grower
Growers: 2nd Most troublesome weed*
* Summed averages are greater than 100% because of multiple votes for most troublesome species/grower
0
10
20
30
40
50
60
70
80
90
100
Perc
ent (
%) o
f gro
wer
s sur
veye
d
2000-2005
2006-2010
Agents: Most troublesome weed
0
20
40
60
80
100
120
Perc
ent (
%) o
f age
nts s
urve
yed
2000-2005
2006-2010
Agents: 2nd Most troublesome weed
0
10
20
30
40
50
60
70
80
90
100Pe
rcen
t (%
) of a
gent
s sur
veye
d
2000-2005
2006-2010