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- Words: 1,990
- Pages: 35
2006-9-8
1
Managing Pest Resistance in Fragmented Farms: An Analysis of the Risk of Bt Cotton in China and its Zero Refuge Strategy and Beyond
Fangbin Qiao1, Jikun Huang2, Scott Rozelle1 and James Wilen1 1 University 2
of California, Davis Chinese Academy of Sciences
Presented at the “Economic Consideration of Biosafety and Biotechnology Regulations in India: A Policy Dialogue” August 24-25, 2006, The Claridges, New Delhi, India
Authors note: The authors acknowledge the financial support of the Economy and Environment Program for Southeast Asia (EEPSEA) and National Science Foundation of China (70021001 and 70333001). 2006-9-8
2
Introduction • The development of Bacillus thuringiensis (Bt) crops has been the most successful application of agricultural biotechnology 2002: 20% cotton 9% maize • One of the major worries lurking behind this success is pest resistance. 2006-9-8
3
Introduction – cont. To counter the threat of resistance – refuge strategy. Bt field
Non-Bt field
Resistant Pests
Susceptible Pests
Mating
Slow down the buildup of the resistance in the pest population 2006-9-8
4
Introduction – cont. • Refuge policy – Refuge requirement in the US, 5% non-spray or 20% spray – All the other Bt countries follow – Except for China: 0% refuge
• Question: all the empirical studies is in US, is it really suitable for all the other Bt countries? 2006-9-8
5
Objective • Is US-styled refuge policy appreciate for all Bt countries, including developing countries? • If not, what is the optimal refuge policy to manage pest resistance in a developing country?
2006-9-8
6
Why China? • One of the leaders in the creation and use of Bt crops in the world: – Largest Bt cotton planting country • 3.7 million ha in 2004, 66% of all the cotton
– 0% refuge policy
• Empirical data 2006-9-8
7
Main topics • Cotton, Cotton Bollworm and Cropping System in China • The Model • Simulation Result • Conclusion and Discussion 2006-9-8
8
Cotton, cotton bollworm and cropping system: Cotton and Bt cotton in China
2006-9-8
9
Cotton, cotton bollworm and cropping system: Cotton and Bt cotton in China – cont. 4000 Yel l ow Ri ver va l l ey Yangt s e Ri ver val l ey Nor t hwes t
(1000 tons)
3000
2000
1000
2006-9-8
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
1989
1988
1987
1986
1985
1984
1983
1982
1981
1980
1979
0
10
Cotton, cotton bollworm and cropping system:
Bt cotton adoption rate, 1997-2004
100
Sown area of Bt & non-Bt cotton in China, 1997-2004
0
0
20
40
(%)
60
(1,000 ha) 2000 4000
80
6000
Cotton and Bt cotton in China – cont.
1997
1998
1999
2000 non-Bt cotton
2006-9-8
2001
2002 Bt cotton
2003
2004
1997
1998
1999 Hebei
2000
2001 Shandong
2002
2003
2004
Henan
11
Cotton, cotton bollworm and cropping system: Cotton and Bt cotton in China – cont. • Yellow River Valley cotton production region became the largest cotton production after the 1980s • However, production decreases since early 1990s • Pest problem, especially the cotton bollworm is the most important pest • Bt cotton spread rapidly in China, especially in Yellow River Valley 2006-9-8
12
Cotton, cotton bollworm and cropping system: Cotton bollworm
2006-9-8
13
Cotton, cotton bollworm and cropping system: Cotton bollworm - cont. Actual loss (%) of grain and cotton China
Potential loss (%) of cotton
Yellow River Valley
Cotton
Grain
Cotton
Grain
China
Yellow River Valley
1990
5
3
8
4
24
35
1992
14
2
29
3
45
93
1997
6
2
9
3
35
62
2006-9-8
14
Cotton, cotton bollworm and cropping system: Cotton bollworm - cont. •
The CBW is the most important pest in China’s cotton production regions, especially in Yellow River Valley (YRV) – Without spray: potential yield loss: • Official estimation: 24-50% (China), 35-93% (YRV) • Some farmers even say: 100% in YRV
– With spray: in 1992 • 14% in China • 29% in YRV • More than 50% in some place in YRV
2006-9-8
15
Cotton, cotton bollworm and cropping system: Cotton bollworm - cont. Resistant factor of cotton bollworm to pyrethroid from 1981 to 1995, China
180 160 140 120 100 80 60 40 20 0
Resistance of cotton bollworm to Bt toxin in the lab
(resistant factor)
120 100 80 60 40 20 0 1 5 9 10 13 14 15 16 18 25 30 33 36 38 44
1981
2006-9-8
1985
1987
1995
(generation)
16
Cotton, cotton bollworm and cropping system: Cotton bollworm - cont. • The CBW developed resistance to any conventional pesticides in only 10/20 years • More pesticides use – Per hectare pesticide cost in 1995 price ($/ha) • 31 in 1980 to 101 in 1995
– Share (%) of pesticide cost in total material costs of crop production • 13% in 1980 to 22% in 1995 2006-9-8
17
Cotton, cotton bollworm and cropping system • Cotton bollworm (CBW) is the most important pest, especially in Yellow River Valley • CBW developed resistance to conventional pesticides (field data), and Bt toxin (lab data) • Should China plant non-Bt cotton as refuge? – Yes, all the other Bt countries did – No, special cropping system (natural refuge crops)
2006-9-8
18
Cotton, cotton bollworm and cropping system: Cropping system in Yellow River Valley
2006-9-8
19
Cotton, cotton bollworm and cropping system: Cropping system in Yellow River Valley – cont.
2006-9-8
20
Cotton, cotton bollworm and cropping system: no field evidence of buildup of resistance to Bt toxin
Cotton bollworm Region
Pink bollworm
N.China
N. Carolina
Arizona
Initial (year)
0.0095 (1998)
0.00043 (2000)
0.16 (1997)
Final (year)
0.0022 (2000)
0 (2001)
0.075 (2001)
2006-9-8
21
Cotton, cotton bollworm and cropping system: Natural refuge crops • CBW can easily find nature refuge crops: – 1st generation: wheat only – 2nd and 3rd generations: soybean, peanuts, weeds, fruit trees, etc. – 4th generation: soybean, peanuts, weeds, fruit trees, etc. + CORN
• Is planting non-Bt cotton as refuge economic? – need quantitatively analysis
2006-9-8
22
The model: biological part •
Susceptibility to Bt toxin (or conventional pesticide) is considered as the good “resource”
•
Two-locus four-allele model • Susceptible gene to Bt toxin • Susceptible gene to conventional pesticide
•
The susceptibility (X) and resistant (x) alleles to Bt toxin at locus one, and the susceptibility (Y) and resistant (y) alleles to conventional pesticide at locus two divided the total pest population into nine types of pests with different genotypes.
•
Two treatment (Bt cotton and conventional pesticide) divided all the land into four type: Bt cotton with CP spray; Bt cotton without CP spray; Non-Bt cotton with CP spray; Non-Bt cotton without spray and natural refuge crops
2006-9-8
23
The model: biological part • Three state variables: – Dynamic of total pest population – Dynamic of the fraction of the susceptible gene to Bt toxin in the total pest population – Dynamic of the fraction of the susceptible gene to conventional pesticide in the total pest population
•
two control variables: – Bt cotton – Conventional pesticide spray
•
renewable resource model
2006-9-8
24
A simple sketch figure of the biological part of the model New pests
Bt field Spray
No-Spray
Non-Bt refuge Natural Spray
Refuge No-Spray crops
death
2006-9-8
25
The model: biological part Nine genotype pests, their fractions in the total pest population, and mortality rate in different fields
2006-9-8
26
The model: regulatory part • A social planer minimize the total cost: – Damage cost caused by the pests – Control costs of Bt cotton – Control costs of conventional pesticide
• Subject to change of the total pest population and the change of the resources. 2006-9-8
27
The model Min
t =T
t =1 0 ≤ qt ≤1
V ( D t ) = DCTN t * α + cbt * q t + ccp * [ q t * dbt t + (1 − q t ) * dnbt t ] + δ V ( D t +1 )
geno = 9
∑ MR
D t +1 − D t = g * D t * (1 − D t ) −
geno t
, Dt=0 = D 0
geno =1 geno=3
∑
wt +1 − wt = (1 −wt ) * (wt2 * g * Dt * (1 − Dt ) −
geno=6
MRtgeno ) + (0.5 − wt ) * (2 * wt * (1 − wt ) * g * Dt * (1 − Dt ) −
geno=1
∑MR
geno ) t
geno=4
geno=9
+ (wt ) * ((1 − wt ) 2 * g * Dt * (1 − Dt ) −
∑ MR
geno ), wt =0 t
= w0
geno=7
geno=1, 4,7
vt +1 − vt = (1 −v t ) * (vt2 * g * Dt * (1 − Dt ) −
∑
geno=2,5,8
MRtgeno ) + (0.5 − vt ) * (2 * vt * (1 − vt ) * g * Dt * (1 − Dt ) −
∑ MR
geno ) t
geno=3,6,9
+ (v t ) * ((1 − vt ) 2 * g * Dt * (1 − Dt ) −
2006-9-8
∑ MR
geno ), vt =0 t
= v0
28
Parameters • Biological parameters: calculating using data from Institute of Plant Protection of the Chinese Academy of Agricultural Sciences , and their publications • Economic parameters: calculating using data from Center for Chinese Agricultural Policy of the Chinese Academy of Sciences, and their publications 2006-9-8
29
Parameters: default value Economic parameters Unit damage cost caused by the CBW Bt cotton planting cost Conventional pesticide spray cost Discount rate Biological parameters Initial resistant (to Bt toxin) gene frequency Initial resistant (to conventional pesticide) gene frequency Mortality rate of susceptible pest to Bt toxin in Bt field
Default value
Source
$1030/ha
0.036
Calculated based on data collected by IPPa Calculated based on data collected by CCAPb Calculated based on data collected by CCAPb The people’s bank of China
0.001
Gould, 1998; Livingston et al., 2002
$143/ha $252/ha
0.50
Ru et al., 2002; Wu, 2000
0.90
Mortality rate of susceptible pest to conventional pesticides if spray Fitness cost of resistant pests to Bt toxin Fitness cost of resistant pests to conventional pesticides Dominance of susceptible gene (to Bt toxin) in heterozygote Dominance of susceptible gene (to conventional pesticide) in heterozygote
0.90
Wu et al., 2000; Livingston et al., 2002; Storer et al. 2003; Mike Caprio, 2000 No data
0.05
Livingston et al., 2002
0.05
No data
0.75
Private discussion with Wu
0.75
No data
The threshold value for spray Natural growth rate
0.28 0.68
Guo (1999?) Calculated by the author using field date
a b
IPP is the Institute of Plant Protection of the Chinese Academy of Agricultural Science. CCAP is the Center for Chinese Agricultural Policy (CCAP) of the Chinese Academy of Sciences (CAS).
2006-9-8
30
Simulation result • Optimal refuge size for – 10-year plan: 0% – 15-year plan: 0%
2006-9-8
31
Simulation result
2006-9-8
32
Simulation result: 20-year plan Cost of zero refuge policy and optimal dynamic refuge policy for 20-year plan
2006-9-8
Zero refuge policy
Optimal dynamic policy
Cost saving from zero refuge policy to optimal dynamic refuge strategy
Average cost (US$ per ha per year)
Average cost (US$ per ha per year)
In absolute value (US$ per ha per year)
In percentage (%)
176.83
174.37
2.46
1.39
33
Simulation result: 20-year plan – cont.
• Transaction costs are ignored in the model – Cost associated with enforcement – Monitoring cost
• Monitoring cost: US $ 6.97 per hectare per years >> US $ 2.46
2006-9-8
34
Conclusion and discussion • China does not need to re-think its zero refuge policy • Does not mean zero refuge is right – if Bt corn is commercialized – if Bt rice is commercialized
• Other developing countries: need quantitative analysis because of – Nature of the pest – Nature of the cropping system
2006-9-8
35
1
Managing Pest Resistance in Fragmented Farms: An Analysis of the Risk of Bt Cotton in China and its Zero Refuge Strategy and Beyond
Fangbin Qiao1, Jikun Huang2, Scott Rozelle1 and James Wilen1 1 University 2
of California, Davis Chinese Academy of Sciences
Presented at the “Economic Consideration of Biosafety and Biotechnology Regulations in India: A Policy Dialogue” August 24-25, 2006, The Claridges, New Delhi, India
Authors note: The authors acknowledge the financial support of the Economy and Environment Program for Southeast Asia (EEPSEA) and National Science Foundation of China (70021001 and 70333001). 2006-9-8
2
Introduction • The development of Bacillus thuringiensis (Bt) crops has been the most successful application of agricultural biotechnology 2002: 20% cotton 9% maize • One of the major worries lurking behind this success is pest resistance. 2006-9-8
3
Introduction – cont. To counter the threat of resistance – refuge strategy. Bt field
Non-Bt field
Resistant Pests
Susceptible Pests
Mating
Slow down the buildup of the resistance in the pest population 2006-9-8
4
Introduction – cont. • Refuge policy – Refuge requirement in the US, 5% non-spray or 20% spray – All the other Bt countries follow – Except for China: 0% refuge
• Question: all the empirical studies is in US, is it really suitable for all the other Bt countries? 2006-9-8
5
Objective • Is US-styled refuge policy appreciate for all Bt countries, including developing countries? • If not, what is the optimal refuge policy to manage pest resistance in a developing country?
2006-9-8
6
Why China? • One of the leaders in the creation and use of Bt crops in the world: – Largest Bt cotton planting country • 3.7 million ha in 2004, 66% of all the cotton
– 0% refuge policy
• Empirical data 2006-9-8
7
Main topics • Cotton, Cotton Bollworm and Cropping System in China • The Model • Simulation Result • Conclusion and Discussion 2006-9-8
8
Cotton, cotton bollworm and cropping system: Cotton and Bt cotton in China
2006-9-8
9
Cotton, cotton bollworm and cropping system: Cotton and Bt cotton in China – cont. 4000 Yel l ow Ri ver va l l ey Yangt s e Ri ver val l ey Nor t hwes t
(1000 tons)
3000
2000
1000
2006-9-8
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
1989
1988
1987
1986
1985
1984
1983
1982
1981
1980
1979
0
10
Cotton, cotton bollworm and cropping system:
Bt cotton adoption rate, 1997-2004
100
Sown area of Bt & non-Bt cotton in China, 1997-2004
0
0
20
40
(%)
60
(1,000 ha) 2000 4000
80
6000
Cotton and Bt cotton in China – cont.
1997
1998
1999
2000 non-Bt cotton
2006-9-8
2001
2002 Bt cotton
2003
2004
1997
1998
1999 Hebei
2000
2001 Shandong
2002
2003
2004
Henan
11
Cotton, cotton bollworm and cropping system: Cotton and Bt cotton in China – cont. • Yellow River Valley cotton production region became the largest cotton production after the 1980s • However, production decreases since early 1990s • Pest problem, especially the cotton bollworm is the most important pest • Bt cotton spread rapidly in China, especially in Yellow River Valley 2006-9-8
12
Cotton, cotton bollworm and cropping system: Cotton bollworm
2006-9-8
13
Cotton, cotton bollworm and cropping system: Cotton bollworm - cont. Actual loss (%) of grain and cotton China
Potential loss (%) of cotton
Yellow River Valley
Cotton
Grain
Cotton
Grain
China
Yellow River Valley
1990
5
3
8
4
24
35
1992
14
2
29
3
45
93
1997
6
2
9
3
35
62
2006-9-8
14
Cotton, cotton bollworm and cropping system: Cotton bollworm - cont. •
The CBW is the most important pest in China’s cotton production regions, especially in Yellow River Valley (YRV) – Without spray: potential yield loss: • Official estimation: 24-50% (China), 35-93% (YRV) • Some farmers even say: 100% in YRV
– With spray: in 1992 • 14% in China • 29% in YRV • More than 50% in some place in YRV
2006-9-8
15
Cotton, cotton bollworm and cropping system: Cotton bollworm - cont. Resistant factor of cotton bollworm to pyrethroid from 1981 to 1995, China
180 160 140 120 100 80 60 40 20 0
Resistance of cotton bollworm to Bt toxin in the lab
(resistant factor)
120 100 80 60 40 20 0 1 5 9 10 13 14 15 16 18 25 30 33 36 38 44
1981
2006-9-8
1985
1987
1995
(generation)
16
Cotton, cotton bollworm and cropping system: Cotton bollworm - cont. • The CBW developed resistance to any conventional pesticides in only 10/20 years • More pesticides use – Per hectare pesticide cost in 1995 price ($/ha) • 31 in 1980 to 101 in 1995
– Share (%) of pesticide cost in total material costs of crop production • 13% in 1980 to 22% in 1995 2006-9-8
17
Cotton, cotton bollworm and cropping system • Cotton bollworm (CBW) is the most important pest, especially in Yellow River Valley • CBW developed resistance to conventional pesticides (field data), and Bt toxin (lab data) • Should China plant non-Bt cotton as refuge? – Yes, all the other Bt countries did – No, special cropping system (natural refuge crops)
2006-9-8
18
Cotton, cotton bollworm and cropping system: Cropping system in Yellow River Valley
2006-9-8
19
Cotton, cotton bollworm and cropping system: Cropping system in Yellow River Valley – cont.
2006-9-8
20
Cotton, cotton bollworm and cropping system: no field evidence of buildup of resistance to Bt toxin
Cotton bollworm Region
Pink bollworm
N.China
N. Carolina
Arizona
Initial (year)
0.0095 (1998)
0.00043 (2000)
0.16 (1997)
Final (year)
0.0022 (2000)
0 (2001)
0.075 (2001)
2006-9-8
21
Cotton, cotton bollworm and cropping system: Natural refuge crops • CBW can easily find nature refuge crops: – 1st generation: wheat only – 2nd and 3rd generations: soybean, peanuts, weeds, fruit trees, etc. – 4th generation: soybean, peanuts, weeds, fruit trees, etc. + CORN
• Is planting non-Bt cotton as refuge economic? – need quantitatively analysis
2006-9-8
22
The model: biological part •
Susceptibility to Bt toxin (or conventional pesticide) is considered as the good “resource”
•
Two-locus four-allele model • Susceptible gene to Bt toxin • Susceptible gene to conventional pesticide
•
The susceptibility (X) and resistant (x) alleles to Bt toxin at locus one, and the susceptibility (Y) and resistant (y) alleles to conventional pesticide at locus two divided the total pest population into nine types of pests with different genotypes.
•
Two treatment (Bt cotton and conventional pesticide) divided all the land into four type: Bt cotton with CP spray; Bt cotton without CP spray; Non-Bt cotton with CP spray; Non-Bt cotton without spray and natural refuge crops
2006-9-8
23
The model: biological part • Three state variables: – Dynamic of total pest population – Dynamic of the fraction of the susceptible gene to Bt toxin in the total pest population – Dynamic of the fraction of the susceptible gene to conventional pesticide in the total pest population
•
two control variables: – Bt cotton – Conventional pesticide spray
•
renewable resource model
2006-9-8
24
A simple sketch figure of the biological part of the model New pests
Bt field Spray
No-Spray
Non-Bt refuge Natural Spray
Refuge No-Spray crops
death
2006-9-8
25
The model: biological part Nine genotype pests, their fractions in the total pest population, and mortality rate in different fields
2006-9-8
26
The model: regulatory part • A social planer minimize the total cost: – Damage cost caused by the pests – Control costs of Bt cotton – Control costs of conventional pesticide
• Subject to change of the total pest population and the change of the resources. 2006-9-8
27
The model Min
t =T
t =1 0 ≤ qt ≤1
V ( D t ) = DCTN t * α + cbt * q t + ccp * [ q t * dbt t + (1 − q t ) * dnbt t ] + δ V ( D t +1 )
geno = 9
∑ MR
D t +1 − D t = g * D t * (1 − D t ) −
geno t
, Dt=0 = D 0
geno =1 geno=3
∑
wt +1 − wt = (1 −wt ) * (wt2 * g * Dt * (1 − Dt ) −
geno=6
MRtgeno ) + (0.5 − wt ) * (2 * wt * (1 − wt ) * g * Dt * (1 − Dt ) −
geno=1
∑MR
geno ) t
geno=4
geno=9
+ (wt ) * ((1 − wt ) 2 * g * Dt * (1 − Dt ) −
∑ MR
geno ), wt =0 t
= w0
geno=7
geno=1, 4,7
vt +1 − vt = (1 −v t ) * (vt2 * g * Dt * (1 − Dt ) −
∑
geno=2,5,8
MRtgeno ) + (0.5 − vt ) * (2 * vt * (1 − vt ) * g * Dt * (1 − Dt ) −
∑ MR
geno ) t
geno=3,6,9
+ (v t ) * ((1 − vt ) 2 * g * Dt * (1 − Dt ) −
2006-9-8
∑ MR
geno ), vt =0 t
= v0
28
Parameters • Biological parameters: calculating using data from Institute of Plant Protection of the Chinese Academy of Agricultural Sciences , and their publications • Economic parameters: calculating using data from Center for Chinese Agricultural Policy of the Chinese Academy of Sciences, and their publications 2006-9-8
29
Parameters: default value Economic parameters Unit damage cost caused by the CBW Bt cotton planting cost Conventional pesticide spray cost Discount rate Biological parameters Initial resistant (to Bt toxin) gene frequency Initial resistant (to conventional pesticide) gene frequency Mortality rate of susceptible pest to Bt toxin in Bt field
Default value
Source
$1030/ha
0.036
Calculated based on data collected by IPPa Calculated based on data collected by CCAPb Calculated based on data collected by CCAPb The people’s bank of China
0.001
Gould, 1998; Livingston et al., 2002
$143/ha $252/ha
0.50
Ru et al., 2002; Wu, 2000
0.90
Mortality rate of susceptible pest to conventional pesticides if spray Fitness cost of resistant pests to Bt toxin Fitness cost of resistant pests to conventional pesticides Dominance of susceptible gene (to Bt toxin) in heterozygote Dominance of susceptible gene (to conventional pesticide) in heterozygote
0.90
Wu et al., 2000; Livingston et al., 2002; Storer et al. 2003; Mike Caprio, 2000 No data
0.05
Livingston et al., 2002
0.05
No data
0.75
Private discussion with Wu
0.75
No data
The threshold value for spray Natural growth rate
0.28 0.68
Guo (1999?) Calculated by the author using field date
a b
IPP is the Institute of Plant Protection of the Chinese Academy of Agricultural Science. CCAP is the Center for Chinese Agricultural Policy (CCAP) of the Chinese Academy of Sciences (CAS).
2006-9-8
30
Simulation result • Optimal refuge size for – 10-year plan: 0% – 15-year plan: 0%
2006-9-8
31
Simulation result
2006-9-8
32
Simulation result: 20-year plan Cost of zero refuge policy and optimal dynamic refuge policy for 20-year plan
2006-9-8
Zero refuge policy
Optimal dynamic policy
Cost saving from zero refuge policy to optimal dynamic refuge strategy
Average cost (US$ per ha per year)
Average cost (US$ per ha per year)
In absolute value (US$ per ha per year)
In percentage (%)
176.83
174.37
2.46
1.39
33
Simulation result: 20-year plan – cont.
• Transaction costs are ignored in the model – Cost associated with enforcement – Monitoring cost
• Monitoring cost: US $ 6.97 per hectare per years >> US $ 2.46
2006-9-8
34
Conclusion and discussion • China does not need to re-think its zero refuge policy • Does not mean zero refuge is right – if Bt corn is commercialized – if Bt rice is commercialized
• Other developing countries: need quantitative analysis because of – Nature of the pest – Nature of the cropping system
2006-9-8
35
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