Transcript Document

Growing Herbicide Resistant
Crops Sustainably:
What Farmers Are (and Are Not) Doing
George Frisvold
Department of Agricultural & Resource Economics
University of Arizona
17th ICABR Conference
Innovation & Policy for the Bioeconomy
Ravello, Italy
June 18-21, 2013
Adoption of Herbicide
Resistant Crops in the US
100
90
% of planted acres
80
70
60
50
40
30
Corn
20
Cotton
10
Soybeans
0
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012
USDA, ERS
Claimed Environmental Benefits
of HR Crops
Increased adoption of conservation tillage
Reduced soil erosion
Reduced carbon emissions
Substitution to less toxic and persistent herbicides
Evidence regarding conservation tillage adoption
stronger than for herbicide substitution
Effects on Impact-Adjusted
Herbicide Use
Much cited evidence based on ex ante
opinion surveys of extension specialists
Good micro-level studies that account for
selection bias sometimes consistent with
expert opinion, sometimes not
Formal comparisons of expert opinion and
actual on-farm behavior lacking
Reduced Diversity of Weed
Control Tactics
Increased reliance on chemical control
Increased reliance on a single
mechanism of action (MOA) within
chemical control
Enormous selection pressure for HR
weeds
US pesticide applications in
kilotons
Total Pesticides
Total Herbicides
Corn
Cotton
Soybeans
Herbicide a.i / Total a.i
USDA, NASS
1964
1995
2005
97.5
21.9
11.6
2.1
1.9
22%
235.7
146.1
84.5
14.7
30.9
62%
222.8
144.6
76.4
13.1
38.9
65%
Specific crop herbicide ai as a %
of total herbicide ai
Corn
Cotton
Soybeans
Three Crops
USDA, NASS
1964
1995
2005
53%
10%
9%
71%
58%
10%
21%
89%
53%
9%
27%
89%
Glyphosate Kg of active ingredient (a.i.) applied as a
% of total Kg of herbicide a.i. applied
Crop
Year
Percent
Corn
1997
1
1999
3
2005
15
2010
35
1995
11
1999
54
2006
89
1995
3
1999
20
2005
57
2010
62
Soybeans
Cotton
USDA, NASS
Herbicides applied to corn by
herbicide family and MOA
% of total
herbicide hectaretreatments
1996
2005
2
19
Herbicide family
Phosphinic acid
Mechanism of action
G(9)
Triazine
Amides
Benzoic / Phenoxy
Sulfonylurea
C1(5)
K3(15)
O(4)
B(2)
38
27
15
11
48
4
5
5
Pyridine
Other herbicides
F1(12)
0
8
6
9
USDA, NASS
Herbicides applied to cotton by
herbicide family and MOA
% of total
herbicide hectaretreatments
1996
2007
3
60
Herbicide family
Phosphinic acid
Mechanism of action
G(9)
Dinitroaniline
Urea
Triazine
Organic arsenical
K1(3)
C2(7)
C1(5)
Z(17)
26
20
13
12
14
6
2
1
Benzothiadiazole
Other herbicides
C3(6)
3
23
1
17
USDA, NASS
Herbicides applied to soybeans by
herbicide family and MOA
% of total herbicide
hectare-treatments
Herbicide family
Mechanism of action
1996
2006
Phosphinic acid
G(9)
10
77
Dinitroaniline
K1(3)
20
3
Imidazolinone
B(2)
21
2
Sulfonylurea
B(2)
9
NA2
Diphenyl ether
E(14)
8
1
Oxime
A(1)
7
1
Aryloxyphenoxy propionic acid
A(1)
7
NA
Phenoxy
O(4)
5
5
Amides
K3(15)
4
2
Triazine
C1(5)
4
1
Benzothiadiazole
C3(6)
4
NA
2
6
Other herbicides
Planned glyphosate resistant (GR) crop
plantings and residual herbicide use from a
survey of 1,205 growers
Variable
Corn Soybeans Cotton
2008 GR acreage planned (%)
73
96
92
2008 GR acreage with residual
planned (%)
66
28
66
2008 GR acreage following GR
acreage planned (%)
63
47
68
Hurley et al., 2009b
Fields Scouted for Weeds
100
90
80
% of Acres
70
1996
2000
2005
2006
2007
60
50
40
30
20
10
0
Corn
USDA, ARMS
Soybeans
Cotton
Pre-emergence Weed Control
100
90
80
% of acres
70
1996
2000
2005
2006
2007
60
50
40
30
20
10
0
Corn
USDA, ARMS
Soybeans
Cotton
Post-emergence Weed Control
100
90
80
% of acres
70
1996
2000
2005
2006
2007
60
50
40
30
20
10
0
Corn
USDA, ARMS
Soybeans
Cotton
Cultivation for Weed Control
100
90
80
% of acres
70
1996
2000
2005
2006
2007
60
50
40
30
20
10
0
Corn
USDA, ARMS
Soybeans
Cotton
Percent of respondents who believed growers
were following the practice “less” or “much less”
as a result of HR crop adoption (from internet
survey of agricultural professionals
Practice
% of
respondents
Combination of weed control methods
>60%
Crop rotation for weed control
>40%
Annual rotation of herbicides
>50%
Use of multiple herbicides
>60%
Tillage for weed control
>80%
Harrington et al., 2009
Number of US States with
Glyphosate Resistant Weeds
Number of States
Number of Weeds
Room for improvement in BMP
adoption
Many growers practicing many Best
Management Practices (BMPs) to delay
resistance much of the time, but . . .
. . . adoption of some of the most
critical BMPs remains low
Most Growers Practicing Most
BMPs Much of the Time
Growers adopting practice often or always
Corn
Frisvold et al., 2009
Note similarity in
adoption across crops
Corn
Soybeans
Source: Frisvold et al., 2009
Cotton
Perceptions that Discourage
BMP Adoption
Attribution of spread of resistant weeds to
Natural forces
Neighbors’ behavior
Belief that individual action has little effect on
resistance
As of mid-2000s, low awareness of
How practices affect weed resistance
Importance of rotating herbicides with different
modes of action & use of tank mixes for managing
resistance
Perceptions that Discourage
BMP Adoption
As of early 2000s, low concern over
resistance
Confidence that new products will
become available
Plant Breeders to the Rescue?
New stacked varieties resistant to
multiple herbicides
Reduces reliance on a single MOA
Possibility of “optimal rotations” of MOAs
Not based on new MOAs or compounds
Regulatory approval possibly faster
Summing Up
Pervasive reduction in the diversity of weed
control tactics from mid-1990s to mid-2000s
Significant room for improvement in BMP
adoption, particularly using herbicides with
diverse mechanisms of action
As of mid-2000s, many growers had
perceptions that tend to discourage BMP
adoption
MR varieties seen as short run solution, but
questions remain about strategy
Concerns about Stacked Varieties
with Multiple Resistance (MR)
No new MOAs for some time
Some weeds already resistant to multiple
MOAs
Could generate “hidden” selection pressure
Return to reliance on more persistent and
toxic herbicides