Power Point On Bt Crops

Battling the Two-Edged Sword in China: Controlling Pests with Bt Cotton and Managing Resistance Build-up with Refuge Policies

Fangbin Qiao

Bacillus thuringiensis Bt

On the one hand One the other hand

resistant

Refuge On plots with Bt cotton

resistant

On plots with no Bt cotton

susceptible

Is a US-style refuge policy really suitable for all the other countries?

what are the optimal refuge polices for these countries?

It turns out that to properly model this issue, the context of the study (such as the dynamics of the pest population, the nature of the cropping patterns; etc.) all matter. Therefore, a model on cotton is going to be different than a model on corn

es te

W

n

rn

al

th er

0

C en tr

N or

(%) 60

40

20

9

19 82 19 85 19 88 19 91 19 94 19 97 20 00

19 7

(1,000 tons) 5000

4000

3000

2000

1000

0

Helicoverpa armigera

29

93

On the one hand, On the other hand,

In fact, this was not the first time that the bollworm population built up resistance. During the 1980s, it had built up resistance to organophosphates.

Resistance factor of cotton bollworm to pyrethroid

180 160 140 120 100 80 60 40 20 0 1981

So, farmers had to move to using pyrethroid-based insecticides. The problem in the early 1990s was that there was nothing to move into.

1985

1987

1995

This tendency of the bollworm to evolve resistance is an important characteristic that I

Nice wine! Am I drunk?

(1,000 ha)

6000

4000

2000

0 1997 1998 1999 2000 2001 2002 2003 2004

100

(%)

75 50 25 0 1997 1998 1999 2000 2001 2002 2003 2004

Henan, Shandong, and Hebei are the 2nd, 3rd and 4th largest cotton production provinces in China

Bt is just another pesticide. Will bollworms develop resistance like they did to OPs in the 1980s and Pyrethroids in the 1990s?

120 80 40 0 1

10

18

33

38

44

In the US: non-Bt cotton refuge  natural refuge crop

In China: things are different  There are “natural refuge crops” in the diverse cropping pattern Definition of natural refuge crop: a crop other than cotton that can serve as a host for the cotton bollworm

China’s cropping patterns are different than those in the US where cotton is often mono-cropped across huge areas. The typical view in China is like this. Cotton plots are planted among many different crops. Farms are very diversified

And, so the argument is that China does not need to spend the time and effort developing, enforcing cotton refuges.

In China: things are different  There are “natural refuge crops” in the diverse cropping pattern Definition of natural refuge crop: a crop other than cotton that can serve as a host for the cotton bollworm

So, what are the cropping patterns like in Northern China? Are there natural refuges? I use 3 tapes of data to show this. And information from these data sources are incorporated into my analysis

my family farm (2006)

hosted

CORN

No. 1

Dt + − Dt = g

Dt

− Dt −

geno =

∑MR

geno =

geno t

No. 2 wt + − wt = + wt

− wt − wt

wt

g Dt

− Dt −

− Dt −

g Dt

geno =

geno =

∑ MR

geno =

geno t

+

− wt

wt

− wt

g Dt

− Dt −

geno =

∑ MR

geno =

geno t

∑ MR

geno =

geno t

No. 3 vt + − vt = + vt

−v t − vt

vt

g Dt

g Dt

− Dt −

− Dt −

geno =

geno =

∑ MR

∑ MR

geno t

geno t

+

− vt

vt

− vt

g Dt

− Dt −

geno =

∑ MR

geno t

Min ( ∑t =

t =T

≤ qt ≤ ≤btcpt ≤ ≤ nbtcpt ≤

Dt α + cbt qt + ccp

qt btcpt + − qt

nbtcpt

δt)

t =T

Min

t=

V Dt = Dt α + cbt qt + ccp

nbtcpt + δ V Dt +

qt btcpt + − qt

≤ qt ≤ ≤btcpt ≤ ≤ nbtcpt ≤

Dt + −Dt = g wt + − wt = − wt + wt

− wt

vt + − vt = − v t + vt

− vt

wt g Dt g Dt

− Dt −

− Dt −

vt g Dt g Dt

−Dt −

Dt

geno =

∑ MR

geno =

geno t

∑MR

geno =

+

− wt

geno t

wt

− wt

g Dt

− Dt −

geno =

∑ MR

geno =

geno t

∑ MR

geno =

− Dt −

− Dt −

geno =

geno =

)

geno =

geno t

geno =

∑ MR

∑ MR

geno t

geno t

+

− vt

vt

− vt

g Dt

− Dt −

geno =

∑ MR

geno t

1 .5 0 0.5 1 0

5

(Year)

10

15

1 .8 .6 .4 .2 0 0

5

(Year)

10

15

Even though 100% Bt cotton has been planted for 15 years, because of these natural refuge crops, the share of the susceptible gene to Bt toxin is still high (>80%) at the 15th year.

1 .8 .6 .4 .2 0 0

5

(Year)

10

15

However, if we assume natural refuge crops are not available, or cotton is the only host plant for cotton bollworm, and if 100% Bt cotton has been planted for 15 years, then the share of the susceptible gene to Bt toxin will be very low (near zero) at the 15th year. In other words, pest

1 .8 .6 .4 .2 0 0

5

(Year)

10

15

1 .8 .6 .4 .2 0 0

5

10 (Year)

15

20

1 .5 0 0.5 1 0

5

10 (Year)

15

20

Cost of zero refuge policy and optimal dynamic refuge policy for 20-year plan

1 .5 0 0.5 1 0

20

40

60 (Year)

80

100



Thank you!